[Edwin sherman] advanced_marine_electrics_and_elec(bookos.org)

Advanced Marine Electrics and Electronics

Troubleshooting


TroubleshootingA Manual for Boatowners

and Marine Technicians

Ed Sherman

International Marine / McGraw-HillCamden, Maine • New York • Chicago • San Francisco • Lisbon • London • Madrid • Mexico City • Milan • New Delhi • San Juan • Seoul • Singapore • Sydney • Toronto

Copyright © 2007 by Edwin R. Sherman. All rights reserved. Manufactured in the United States of America. Except as permitted underthe United States Copyright Act of 1976, no part of this publication may be reproduced or distributed in any form or by any means, orstored in a database or retrieval system, without the prior written permission of the publisher.

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Professional

Want to learn more?

To the hundreds of

ABYC Certified Marine

Electricians I’ve had the

pleasure of meeting and

working with over the years.

Keep up the good work!

C O N T E N T S

vi

Foreword by Tim Murphy, Executive Editor, Cruising World xPreface xiAcknowledgments xiii

2 Testing Batteries, Charging Systems, and Starter Circuits,and Measuring Voltage Drop 14

Catalysts for Change 14Conductance Battery Tester 15Diagnostic Meter 22Value and Utility 35

3 Testing Continuity and Tracing Circuits 37

Tone-Generating Circuit Tracer 38Alphanumeric Time Domain Reflectometer 40Value and Utility 44

4 Testing AC and Grounding Systems for Polarity, Voltage Drop,Impedance, and Frequency 46

The SureTest Circuit Analyzer 46Value and Utility 59

5 Temperature Monitoring as a Diagnostic Aid 60

Infrared Heat-Sensing Gun 61Other Uses for Temperature Monitoring 64Value and Utility 65

6 Using Power Factor to Determine Energy Efficiency 67

Understanding Power Factor 67Improving Your Power Factor 68Determining Power Consumption 68

P A R T 1 : E L E C T R I C A L S Y S T E M S T R O U B L E S H O O T I N G 1 3

1 Marine Troubleshooting the Modern Way 1

Finding Your Way 2Electrics versus Electronics 2Basic Troubleshooting Steps 11

For more information about this title, click here

vii

Using a Power Analyzer 71Value and Utility 73

7 Analyzing Harmonic Distortion 74

Do You Need a Scope? 74AC Loads 75Harmonic Distortion 78Value and Utility 82

8 Using a Laptop for Intermittent Problems 83

Laptop Link-Ups 83Real-World Examples 85

9 Testing for Electromagnetic and Radio Frequency Interference 87

Understanding Electromagnetic Interference 87Standards and Regulations 88Common Sources and Victims of Interference 88Tools of the Trade 90

10 Testing for Residual Current and Isolating Its Sources 93

AC Leakage from Appliances 93Using a Clamp-On AC Leak Tester 95AC Leakage from Degraded Insulation 98Using a Megohmmeter 100Value and Utility 101

11 A Basic Corrosion Survey 103

Tools of the Trade 103Underwater Metal Corrosion and Protection Basics 104Conducting a Corrosion Survey 108

12 Grounding Systems 120

Lightning Protection 120Grounding to Minimize RFI Effects 122Comparing ABYC and NMEA Grounding Standards 124Troubleshooting Redux 128

P A R T 2 : M A R I N E E L E C T R O N I C S I N S T A L L A T I O NA N D T R O U B L E S H O O T I N G 12 9

13 Electronic Equipment Installation Guidelines 130

Ergonomics 130Watertight Integrity 133Thermal Limits 133Power Supply 136Guidelines Summary 138

14 Installing Communications and Position-Finding Systemsand Radar 139

Communications Systems 139Position-Finding Systems 148Radar 152

15 Installing Depth Sounders, Weather Systems, and Autopilots 156

Depth Sounders 156Wind- and Weather-Monitoring Instruments 161Autopilots 163

16 Coaxial Cable and Antennas 165

Coaxial Cable Basics 165Choosing Coax for Marine Applications 167Installing Coaxial Cable 169VHF Antennas 174SSB Antennas 177Satellite Television and Radio Antennas 183Cell Phone Antennas 183Radar Antennas 184

17 Onboard Networks 190

Network Types 190NMEA 2000 192Troubleshooting 193The Future of Onboard Power Distribution 196Closing Thoughts 198

viii

ix

Appendix A: Metric Equivalents 200

Appendix B: Resources 201

Appendix C: ABYC Standards of Interest for Marine Electricians

and Boatowners 203

Glossary 204

List of Acronyms 209

Index 211

F O R E W O R D

x

In 1996 I had the good sense to enroll in a course on diesel maintenance at NewEngland Institute of Technology; that much I can take credit for. What I can’t takecredit for was my exquisite good luck at landing in a class taught by Ed Sherman. It

only slowly dawned on me that I was in the presence of one of the country’s great teachersand communicators of marine technology. What I knew immediately, though, was that Iwas getting my money’s worth. In the intervening years Ed has moved on to the AmericanBoat and Yacht Council, where he teaches the teachers on boat technology, and for nearlya decade now, he’s brought his incomparable teaching into Cruising World ’s pages to thebenefit of us all.

You hold in your hand a fine example of his teaching. As our boats have grown morecomplex, truly competent skippers are part systems operators as well as navigators and boathandlers. Consequently, the line between recreational boaters and technicians has blurred.Advanced Marine Electrics and Electronics Troubleshooting may aim at the professionaltechnician—and it hits that target squarely—but for the dedicated boatowner who reallywants to be self-sufficient, this book provides the guidance to solve the most vexing problemsin electrical and electronic systems. If you’re like me and you’re serious about wanting tounderstand all the details that make up today’s boats, you’ll find more than ample paybackfor every moment spent in Ed Sherman’s company. You’ll certainly come away smarter.

—Tim MurphyExecutive Editor, Cruising World

Copyright © 2007 by Edwin R. Sherman. Click here for terms of use.

P R E F A C E

xi

Unlike the first two books I’ve published that discuss marine electrical installations—The Powerboater’s Guide to Electrical Systems and the revision work for the secondedition of the classic 12-Volt Bible by Miner Brotherton—Advanced Marine Electrics

and Electronics Troubleshooting is intended to help serve the needs of marine electrical techni-cians and experienced boatowners who want to use the latest technology and techniques totroubleshoot onboard electrical problems. These earlier works were intended for the lessexperienced boater; this one is not. You won’t see information in this book that explainsOhm’s law or how circuits are designed. Rather I’ve assumed you’ve already grasped thoseconcepts and have more than a rudimentary understanding of how electrical power, bothDC and AC, is distributed around a boat.

Over the years, many have accused me of being somewhat of a “gadget freak” becauseI’m always conducting seminars or writing magazine articles that discuss the use of sophis-ticated “toys” of the sort that are mentioned in this book.

It’s true that I am continually employing new and often unrecognized equipment inmy work—not because I feel any particular need to always have the latest gadgets at hand,but rather because I’m always looking for easier, more efficient, and more exact ways toaccomplish the everyday tasks of the marine electrician. In addition, I’m acutely aware thatmodern boats are not getting any easier to work on—at least not in regard to their electri-cal systems. As the level of sophistication of the modern boat’s electrical system continuesto increase, and the convergence of traditionally distinct electrical and electronic systemscontinues, many of the techniques found within this book are going to become as main-stream as checking the electrolyte level in a battery cell used to be.

I’d like to point out that most of the equipment discussed in this book is really not allthat new, and many readers who have perhaps migrated into boating from informationtechnology (IT) or telecommunications may recognize some of this equipment and feelright at home. The new thing here is my application of this equipment to the marine envi-ronment and the implications of the findings generated by the equipment.

As boat electrical and electronic systems continue to evolve and to look more like thecomputer network of a modern business office, the techniques described in AdvancedMarine Electrics and Electronics Troubleshooting will increasingly become the best—and insome cases, the only—way to get the job done. The digital volt-ohm meter is not dead, ofcourse, but if it’s the only tool at your disposal for electrical troubleshooting, you simplywill not be able to compete as a professional marine technician. And if you’re not a techni-cian, but rather the owner of an electronically sophisticated boat, you’ll find techniqueshere that will make you the master of your boat, not its slave.

If you are looking for ways to save money on equipment for electrical troubleshooting,or want to learn how to diagnose electrical problems with a traditional, low-cost 12-volt


xii

test light, this book is not for you. But if you want to see how the pros are beginning to dothings, read on. The equipment available to the marine troubleshooter keeps getting bet-ter and more sophisticated as more and more microprocessor capabilities are integratedinto new meters. The value that you derive from the use of this equipment will quicklyoutweigh the initial purchase price, and the benefits will continue to accrue as time goeson. I hope you benefit from the information and approaches I’ve presented in this bookand, as always, happy boating.

preface

A C K N O W L E D G M E N T S

xiii

Besides the many technicians I’ve had the pleasure of working with, this book wouldnot have been possible without the help and guidance of several individuals and twoorganizations in particular.

First, I’d like to thank the American Boat and Yacht Council in general, and most espe-cially for the technical guidance provided by its Standards and Technical Reports for SmallCraft. Without these standards we (boaters, field technicians, and I) would be flying blindwhen performing electrical installations.

Next I’d like to thank the National Marine Electronics Association for its InstallationStandards for Marine Electronic Equipment Used on Moderate-Sized Vessels. This documentis the guiding light for the proper installation of the electronic equipment discussed in thebook.

I’d especially like to express gratitude to three individuals for their peer review workand suggestions. Mickey Smith of Boat Systems in Stuart, Florida, is one of the most inno-vative electrical systems designers working today, and has provided me with much insightinto today’s advanced marine electrical systems, and what is just around the corner fortomorrow. Jim Vander Hey of Cay Electronics, Portsmouth, Rhode Island, is one of myformer students, and has advanced to the leading edge of electronics installation, and cur-rently serves as a member of the board of directors for the NMEA. I’m sure he has no ideahow proud it makes me to see his successes. Finally, I’d like to thank Dan Cox of Midtronics,who got me interested in battery conductance testing methodologies and, most recently,in the applications of this technology for troubleshooting voltage drop problems.


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Troubleshooting


C H A P T E R

1Marine Troubleshootingthe Modern Way

Advanced Marine Electrics and Electronics Troubleshooting introduces the technicianor boatowner to some new equipment for troubleshooting electrical systems. Withthis equipment, some of the traditional techniques used by marine electricians

over the years can now be altered or vastly improved upon. The new gear provides moreaccurate information, and many of the traditional troubleshooting steps can be eliminatedaltogether. The microprocessors in these new devices simplify diagnoses that used torequire multiple steps and painstaking labor.

Because much of the information in this book may be new to many readers, it seemsprudent that we first look at some common problems related to electrical and electronicsystems, and then move on to finding solutions to these problems. Rather than using thetraditional tools of electrical troubleshooting, however, I will identify the new equipmentand point you to the chapter that describes how the equipment is used.

My goal throughout this book is to elevate your skills to the next level in diagnosticwork, using the latest in equipment and techniques. If you’re a professional electrician, youwill certainly need these skills as boats continue to evolve into increasingly more complexelectrical/electronic marvels. And if you’re the owner of a sophisticated boat, learning touse this equipment will greatly simplify your life when it comes to diagnosing a problemquickly and with minimal electrical expertise. The equipment really does most of thedetective work for you. Your part consists of understanding and applying the results gen-erated by the gear, and I hope this book gives you much greater insight into that.

With only a few exceptions, all of the instruments discussed cost less than $500—some of them are less than $100 (and one is under $10!). For anyone who works on boatswith complex electrical systems and lots of electronics, these costs can be easily and quicklyjustified by savings in time and increased effectiveness over old troubleshooting methods.As for the more expensive gear, even that can generate relatively quick payback for profes-sionals, while some advanced amateurs who readily drop thousands of dollars on boat“toys” should have no trouble finding practical applications for these useful and highlycapable tools.

To help you build your high-tech toolbox, I’ve placed Toolbox sidebars in every chap-ter describing an instrument. In them, I’ve listed some models and brands that have agood track record to give you a good place to start.

Throughout this book, I’ve included extensive descriptions of specific instruments todemonstrate the functionalities and basic operations for a class of equipment. My use of


these instruments is not an endorsement forany particular brand. Instruments from othermanufacturers may offer comparable or supe-rior functionality to the ones I’ve used here. Ifyou are considering the purchase of a specificpiece of equipment, carefully weigh all factors:pricing, service, warranty terms, availability,and your specific needs for an instrument’sfunctions and capabilities.

Caution: AC circuitry is dangerous!Extreme shock hazards exist. If you are notexperienced and comfortable around ACequipment and troubleshooting, call in aspecialist.

FINDING YOUR WAY

How is this book set up? I’ve divided it intotwo parts, each with specific goals.

Part 1, Electrical Systems Troubleshooting:

• Identifies new methods for troubleshoot-ing electrical circuits (including theengine starting and battery charging sys-tems and the AC and DC distributionsystems).

• Introduces you to test instruments youmay not have seen before, such as thetime domain reflectometer, megohmme-ter, and amp clamp, and explains theircapabilities and applications.

• Provides step-by-step instructions, withaccompanying photos, on how to usethese instruments and apply the results.

• Explains the importance of groundingsystems from the multiple perspectives ofequipment functionality, shock preven-tion, corrosion minimization, and light-ning protection.

Part 2, Marine Electronics Installationand Troubleshooting:

• Addresses the relationship between theelectrical system and marine electronics.

2 marine troubleshooting

• Looks at numerous installation factorsthat influence the functionality of elec-tronic equipment, and tells you how toanticipate and avoid problems before youcut holes and run wires.

• Gives special attention to antennas andcoaxial cable, as they are critical to theproper functioning of many types ofequipment.

• Introduces the cutting edge of onboardwiring—networked systems—to give youa taste of what to expect in the near future.

Let’s begin, then, with a discussion of thetypes of electrical circuits on modern boats,and how to troubleshoot the modern way.

ELECTRICS VERSUSELECTRONICS

Today’s typical modern boat, whether poweror sail, has the potential for carrying a widevariety of circuits and equipment:

• AC-supplied battery chargers• anchor windlass• audio system• bilge pumps and blowers• bow or stern thrusters• electric galley (stove and oven)• electric head sanitation system• electric winches• engine-driven charging circuit• engine instrumentation• engine starter circuit• hot-water heater• inverters• lighting, including navigation lights and

general illumination• navigation and communications

electronics• television

• trim tabs• refrigeration and air-conditioning system• shore-power transformers (isolation trans-

formers) and AC generators

All of these devices can be divided into twobroad categories: electrical systems, which includesuch things as basic shore-power service or thenavigation light circuit on your boat; and elec-tronics, which we can generally categorize ascircuits that distribute data, such as between aGPS receiver and an autopilot.

The common characteristics of these devicesare that they all have a power source, eitherAC or DC, as well as a path for the electricalcurrent to flow. And inevitably, at some pointduring their service life, they will need to berepaired, upgraded, or replaced.

Beyond these, few factors apply across allof the devices, so it is convenient to organizethem into the categories listed below:

1 Electrical systems

• high-amperage motor circuits• low-amperage motor circuits• engine-driven alternator• lighting circuits• engine instrumentation• AC resistive loads (heating elements)• battery chargers and inverters• AC power sources

2 Electronics

• communications equipment• navigation aids• entertainment equipment

Using these categories, I’ve created flow-charts to identify some common problems, theequipment or instrument to use to troubleshootthose problems, and the general step-by-steptesting procedures. (Each test instrument walks

3marine troubleshooting

you through the process via on-screen prompts,so I won’t repeat all those steps here.) I’ve alsoincluded, for comparison, the old method oftroubleshooting, so you can see the greaterefficiency and effectiveness of the new method.Finally, each flowchart gives you a quick refer-ence to the chapter that offers more detailedinformation on the instrument’s use andapplication.

Flowcharts: Electrical Systems

High-Amperage Motor CircuitsThe first category consists of motor circuitswith high current draws. These are really dualcircuits, with a low-amperage control circuitside to activate a relay or solenoid, which thenactivates the high-amperage side to run themotor. Examples include:

• starter motors• anchor windlass• thrusters• electric winches

The troubleshooting procedure is summa-rized in the flowchart on page 4.

Low-Amperage Motor CircuitsThis category includes AC and DC motor cir-cuits of low current draw (relative to the high-amperage motors above):

• refrigeration systems (AC or DC)• bilge pumps• bilge blowers• trim tabs• electric heads and macerator pumps

Unlike the circuits for high-amperagemotors, low-amperage motor circuits typicallydo not have a control side and a high-currentside, and they are usually fed directly by a DCpower supply (although refrigeration systemsmay be powered by AC or DC, or both).

Typical problems with this category of cir-cuits include the following:

• No operation when the switch isactivated.

• Abnormally slow motor operation.

• Frequent tripping of an overcurrentprotection device (such as a circuitbreaker or fuse).

The troubleshooting procedure is summa-rized in the flowcharts on pages 4 and 5.


Confirm integrity of the power source using a conductance battery tester (Chapter 2).

Test both the control side of the circuit (from the activation switch to the relay or solenoid that activates the high-current side of the circuit) and the high-current side, with or without available power.

If the power source is OK, measure voltage drop using a diagnostic meter (Chapter 2).

If the power source is not OK, recharge or replace the batteries.

Check power source integrity with a multimeter, followed by a carbon pile load test of the battery’s ultimate condition (not possible with sealed batteries). If OK, use a multimeter to trace the entire circuit, separately measuring each leg of the circuit, recording the voltage readings, and calculating acceptable voltage drop.

NEW METHOD

OLD METHOD

Slow motor or no motor operation.

SYMPTOM

High-Amperage Motor Circuits

Confirm the integrity of the power source using the conductance battery tester.

The problem may be a tripped breaker or fuse. Remember these devices trip for a reason; simply replacing a fuse may not solve the problem.

Check current draw with an amp clamp and compare to the fuse or breaker rating. Also consider a locked rotor condition. Review Chapter 11 to learn more.

To determine current draw, connect an ammeter in series; in many cases with higher-current-draw circuits, a resistive shunt is required. Making these temporary, hard-wired connections often takes considerable time.

NEW METHOD

OLD METHOD

No operation when the switch

is activated.

SYMPTOM

Low-Amperage Motor Circuits (1)

The Engine-Driven AlternatorThe engine-driven alternator is a uniquedevice—both in its electrical properties and inits function—so it is treated separately.

We’ll assume the mechanical side of thealternator is in good order, the drive belts aretight, and the alternator is securely mountedto the engine. The flowcharts also assume thatthe problem is new, and that previously all waswell with the charging system. There are sev-eral symptom sets related to alternators thatneed to be considered:

1 Undercharging will be manifested as poorbattery performance.

2 Overcharging will show up as either a foulodor in the battery compartment, orswelling of the battery cases or low elec-trolyte levels (if the problem is of longstanding). With sealed batteries, of course,this cannot be checked, nor can you replen-ish levels. If a cell of a sealed battery gassesitself dry, the situation becomes dangerous.The cell can short itself out, and an arcinside the battery can cause an explosion.

3 Electronic “noise” emitted from the alter-nator may interfere with the performance


Assuming no mechanical problem (such as a seized armature bearing) or extreme solids situation (as in the case of a macerator pump), this is probably a voltage drop issue. A diagnostic meter will pinpoint this in one easy step (Chapter 2). An infrared heat gun (Chapter 5) will also be helpful here.

Perform point-by-point voltage drop tests with a multimeter.

NEW METHOD

OLD METHOD

Slow motor operation.

SYMPTOM

Low-Amperage Motor Circuits (2)

of other electronic equipment on boardthe boat.

The troubleshooting procedure is summa-rized in the flowcharts on page 6.

Lighting CircuitsThis category includes all lighting circuits,both AC and DC, with their different powersupply considerations:

• cabin lights• navigation lights• convenience lights

Light circuits are simple. All you need ispower supplied from a source and a good returnpath to ground. The primary concerns are ofcourse electrical continuity and sufficient volt-age throughout the circuit, especially in the caseof navigation lights, which are governed by bothU.S. Coast Guard regulations and AmericanBoat and Yacht Council (ABYC) standards. Theequipment can be very basic (e.g., a multimeter)or extremely sophisticated (e.g., a time domainreflectometer, or TDR). I now use a TDRalmost exclusively for this sort of work.

The troubleshooting procedure is summa-rized in the flowcharts on page 7.


Determine battery condition with a conductance battery tester or diagnostic meter (Chapter 2). This may require connecting the batteries to another charge source to get them to a state of charge that will allow a valid test.

If the battery is serviceable, look for a voltage differential from no-run to engine running at idle.

If no differential exists, then the alternator is not producing. But why?

Verify that field excitation voltage is being supplied to the alternator: measure the magnetic field strength at the alternator with the engine running versus not running. Use a gauss meter for this step (Chapter 9). No measurable field indicates either a fault in the supply circuit to the field or a faulty voltage regulator. Ameasurable magnetic field and novoltage differential indicate a fault within the alternator.

The voltage differential between no-run and run should be between 0.5 to 2.5 volts (V). More than 2.5 V indicates an overcharge and a faulty voltage regulator. Less than 0.5 V (with the alternator running and a lot of DC loads turned on) may indicate an underrated alternator, in which case an upgrade is indicated. To determine if alternator output is enough to meet the demand, perform a DC load analysis by adding the amperage draws for the various appliances.

Determine open-circuit voltage across the battery posts to determine state of charge. If low, charge battery to at least 70% state of charge, then perform a carbon pile load test (not feasible with sealed batteries). If you don’t have access to a carbon pile load tester, disarm the engine so it can’t start, and test voltage across the terminals while cranking the engine with the starter motor (this is not as precise as a carbon pile test, but it will indicate an extremely weak battery). Use a multimeter to test voltage output; use an ammeter to test current output.

Underchargingor overcharging.

SYMPTOM

NEW METHOD

OLD METHOD

Engine-Driven Alternator (1)

With the alternator running, test for noise emissions using a transistor radio set off scale on both the AM and FM bands to “home in” on noise (Chapter 9). The frequency of the noise will change proportionally with engine rpm.

Correcting this may require overhauling the alternator or adding a capacitor-type filter on the alternator output.

Use process of elimination: shut off one piece of equipment at a time to determine the source of noise.

NEW METHOD

OLD METHOD

Electronic noise heard in radio equipment

or indicated by a bad signal-to-noise ratio on a Loran-C system.

SYMPTOM

Engine-Driven Alternator (2)

Engine InstrumentationHere I’ve grouped the engine instrumentationand related gauges as follows:

• voltmeter• tachometer• oil pressure gauge

• fuel gauge• temperature gauge

These devices need battery power to func-tion, but they often work on a variable groundprinciple from a sending unit, or in the case oftachometers, also receive a signal from the

engine. So in effect, they have two sides totheir circuits: the instrument power side, andthe sending unit input side.


AC Resistive LoadsThis category covers AC-powered resistiveloads; i.e., heating elements. These include:

• water heaters• electric ranges and ovens• electric space heaters

These devices have high current drawsand can develop problems over time. You can


If no light, confirm available power and, of course, check the bulb. The TDR works quite well for checking the entire circuit, including the bulb, in one quick step (Chapter 3).

If the bulb is OK, the TDR will indicate a short circuit; if there is a broken filament, it will show an open circuit.

Use a multimeter to check continuity through each leg of the circuit.

OLD METHOD

No light or abnormally dim light.

SYMPTOM

NEW METHOD

Lighting Circuits (1)

OLD METHOD

SYMPTOM

NEW METHOD

Lighting Circuits (2)

Voltage drop is the cause. Use a diagnostic meter (Chapter 2) to isolate the location of the drop in one step. The infrared heat gun may show a hot spot in the circuitry, which can cause excessive voltage drop (Chapter 5).

Use a multimeter to check continuity through each leg of the circuit.

Bulb is glowing but

abnormally dim.

Confirm power and a good ground at the instrument with a basic multimeter.

If no power, repair as needed.

If power and ground are OK, check continuity of the cable between the instrument head and the sending unit. A multimeter is the best tool for this test.

Once the above has been confirmed, check the sender. (Sending units can be checked with a digital volt-ohmmeter [DVOM], but since values are rarely provided in manuals, the results can be misleading.) If grounding the sending unit wire makes the gauge go to full scale with the power turned on, the sender is faulty.

The methods described here follow traditional procedures. Sometimes the good old DVOM is still the best way!

Instrument inoperative.

SYMPTOM

NEW METHOD

OLD METHOD

Engine Instrumentation (1)

save a great deal of troubleshooting time byusing the diagnostic equipment discussed inthis book.


Battery Chargers and InvertersAC-supplied battery chargers, inverters, andinverter chargers have both AC and DC cir-cuitry in the same case. They also have bothAC and DC outputs or inputs. The test equip-ment required will be dictated by whether theproblem is on the DC or AC side.

The troubleshooting procedure is summa-rized in the flowcharts on pages 9–11.

AC Power SourcesAC power sources consist of shore-power iso-lation transformers and AC generators, bothof which are AC current producers. The trans-former is a point of distribution on board theboat; it is supplied by the shore-power feedbut electrically isolated from it. Because thetools of choice here are the full arsenal of ACdiagnostic tools already mentioned, no flow-chart is presented.

• Check amperage and voltage outputs: usethe SureTest tool (Chapter 4).


Use the SureTest tool (Chapter 4) to completely diagnose all power and grounding faults. This tool will save you many steps over using conventional diagnostic methods, and it will perform tests that no other tool can perform.

Use a multimeter to confirm presence of AC voltage. Then isolate each cable and test for resistance with an ohmmeter. There is no safe way to check cabling under load, and no way to test trip rates and times.

NEW METHOD

OLD METHOD

Poor performance (power supply

suspect).

SYMPTOM

AC Resistive Loads (1)

NEW METHOD

OLD METHOD

SYMPTOM


Perform safety check for ground fault leakage.

Use a high-resolution clamp-on AC leak tester to isolate the source of AC leakage current by process of elimination (Chapter 10).

Use a “split cord” to open the grounding conductor, and check current flow with a high-resolution ammeter in series with the ground wire. Takes more steps and has more potential dangers than a high-resolution leak tester.

SuspectedAC leakage.

NEW METHOD

OLD METHOD

SYMPTOM


Conduct power consumption analysis.

Use the WattsUp? tool to analyze the equipment’s power usage over time (Chapter 6).

Use the WattsUp? tool to calculate operating costs of your equipment.

No prior methods existed for performing this task.

Excessivelyhigh electric

bill.

Engine Instrumentation (2)

In the case of a tachometer, the calibration or cylinder number selector on the gauge may be set incorrectly. The number the gauge is set to should be the same as the number of cylinders in the engine.

In the case of oil pressure, fuel, and other level gauges and temperature senders, the sending unit could be faulty. Try a new sender or check resistance values against a known specification provided by the instrument manufacturer as in the previous flowchart (if you are able to find that information).

The methods described here follow traditional procedures. Sometimes the good old DVOM is still the best way!

NEW METHOD

OLD METHOD

Instrument reads

inaccurately.

SYMPTOM


NEW METHOD

OLD METHOD

SYMPTOM


Perform a waveform analysis using an oscilloscope (Chapter 7).

Without an oscilloscope, there is no efficient way to perform this task.

Equipment operates fine on shore power

but malfunctions when powered by an inverter

or generator.

• Diagnose waveform and harmonicsissues: use an oscilloscope (Chapter 7);if a problem is intermittent, use anoscilloscope/laptop combination totrack and record data (Chapter 8).

• For safety reasons, routinely use a Yoko-gawa or similar clamp-on leak tester(Chapter 10).

Flowcharts: Electronic Devices

Here we’ll cover circuits serving electronicequipment, such as audiovisual, navigation,and communications devices:

• autopilots• communications equipment—VHF and

SSB radios• computer or laptop• depth sounders• fishfinders and chartplotters• navigational equipment—GPS and radar• stereo systems• televisions and DVD players• weather monitoring equipment

This category is a bit more complicatedthan electrical systems because it includesboth AC- and DC-powered gear, withslightly different considerations for each. Aswith all devices, the first step is to confirmthe integrity of the power source at thedevice. In the case of these circuits, thatmeans voltage, whether it’s 120 VAC (volts ofalternating current) or 12 or 24 VDC (voltsof direct current). In many cases, however,you may need to take additional steps.

The troubleshooting procedure for naviga-tion and communications equipment is sum-marized in the flowcharts on pages 11 and 12.For troubleshooting audio and video systemspowered by AC current, see the bottom flow-chart on page 12.

Inverter AC output*: Perform a waveform analysis to look for harmonic distortion that may affect the equipment. Use a true RMS multimeter** or, preferably, an oscilloscope (Chapter 7).

*Ideal Industries does not recommend using the SureTest (Chapter 4) on inverters, but I have used it successfully on true-sine-wave inverters.**True RMS multimeters are discussed in the Powerboater's Guide to Electrical Systems. Simply put, true RMS describes the algorithm a meter must have to accurately analyze a less than perfect AC waveform. Most common meters use an average responding algorithm.

Using a conventional multimeter, perform multiple steps using a “split” shore cord adapter to take voltage and current measurements in the hot, neutral, and ground conductors. This method doesn’t have the advantages of data logging.

NEW METHOD

OLD METHOD

Equipment operates fine on shore power

but malfunctions when powered by an

inverter.

Battery Chargers and Inverters (1)

SYMPTOM

1 0 marine troubleshooting

NEW METHOD

OLD METHOD

SYMPTOM


Inverter DC input: Test amperage draw and excessive voltage drop from the battery supply with a diagnostic meter (Chapter 2).

Using a conventional multimeter, perform multiple steps using a “split” shore cord adapter to take voltage and current measurements in the hot, neutral, and ground conductors. This method doesn’t have the advantages of data logging.

Low AC output voltage.

Batteries keep going dead. The charger is functioning, and the

batteries have been tested and should be able to accept a charge.

NEW METHOD

OLD METHOD

SYMPTOM


Battery charger DC output: An oscilloscope (Chapter 7), or other DVOM with data-logging capability, perhaps connected to a laptop computer if an intermittent problem is suspected (Chapter 8), would be a great choice for tracking both amperage and voltage outputs over time.

Using a conventional multimeter, perform multiple steps using a "split" shore cord adapter to take voltage and current measurements in the hot, neutral, and ground conductors. This method doesn’t have the advantages of data logging.

Battery charger AC input: Use the SureTest tool to use to confirm proper power supply to the battery charger (Chapter 4).

Using a conventional multimeter, perform multiple steps using a “split” shore cord adapter to take voltage and current measurements in the hot, neutral, and ground conductors. This method doesn't have the advantages of data logging.

NEW METHOD

OLD METHOD

No outputfrom the battery

charger.


SYMPTOM

1 1marine troubleshooting

NEW METHOD

OLD METHOD

SYMPTOM

Using a conventional multimeter, perform multiple steps using a "split" shore cord adapter to take voltage and current measurements in the hot, neutral, and ground conductors. This method doesn’t have the advantages of data logging.


Use the Yokogawa or similar clamp-on leak tester to isolate any ground fault leakage on the AC side of these devices (Chapter 10).

Suspected AC leakage from battery charger or inverter

output.

BASIC TROUBLESHOOTINGSTEPS

Over the years, I’ve taught troubleshooting indozens of classrooms and seminars. While theequipment necessary to solve more complicatedproblems has become more sophisticated, thebasic processes haven’t changed. Problem solv-ing is not always easy, and to be done properlyand efficiently, several steps must be taken inlogical order:

1 Verify the problem. Does the complaintrepresent a genuine problem? Or is thesolution really awareness or education?

2 Gather information. Get the com-plaint directly, not thirdhand. Deter-mine the exact symptoms and the condi-tions under which the problem occurs.Get a timeline—is this a new problem, orhas it been going on for awhile? Get asmuch history about the boat as possible.

NEW METHOD

OLD METHOD

SYMPTOM

Confirm proper power to electronic equipment. Use a SureTest tool for AC equipment (Chapter 4) and a DVOM for DC equipment.

Check the integrity of the ground and all of its connections. Use a TDR (Chapter 3) or a diagnostic meter (Chapter 2).

If the gear relies on an antenna, use a TDR to test coaxial connections and cable run. Also, make sure the run is routed correctly as described in Chapter 16.

Use a multimeter and/or a trouble light to track through circuits from one termination point to another. Some termination points may be inaccessible.

Audible or visual“noise” (the latter seen on readouts or monitors

as hash marks or inexplicable lines on

the screen).

Electronics (1)

Try to determine the order in whichsymptoms developed.

3 Determine probable causes. Perform athorough visual inspection, and repairobvious problems before diving intolengthy testing procedures. Have theappropriate service manual or wiringdiagrams available if at all possible(unfortunately, this is often not possible).Think about subsystems and ancillarycomponents that could contribute to orcause the problem.

4 Narrow the list of causes. Use the historyand symptom conditions to narrow downthe list of probable causes. If more than

one symptom exists, are there commoncauses? Avoid preconceived ideas. Followtest procedures step by step, skippingnone.

5 Test all subsystems. Test the most likelycause first. Follow any manufacturer-recommended procedures.

Following these logical steps to trou-bleshooting may seem like the medical historya doctor gathers when trying to figure outwhat ails you, and for good reason: themethod works. Used in combination with thebest, most capable equipment, this methodwill definitely increase your odds for success.Now let’s get started!

1 2 marine troubleshooting

Use an oscilloscope to check AC power quality and harmonics (Chapter 7).

If the symptom is only present when the device is powered by one AC power source versus another, the problem is almost always related to AC waveform or harmonic distortion. Use an oscilloscope to pinpoint.

Use process of elimination, which is often time consuming and frustrating.

NEW METHOD

OLD METHOD

Audio and video systems affected by “bad”

power: random diagonal lines showing on screens and

background noise is heard over speakers/radio.

SYMPTOM

Electronics (3)

NEW METHOD

OLD METHOD

SYMPTOM

Use a multimeter set to ohms to track through circuits from one termination point to another. Some termination points may be inaccessible.

Use a TDR to check the integrity of the network cable (Chapter 3).

Use process of elimination if necessary and be sure to check all individual conductors in the cable.

One electronic device is not “talking” to another

(e.g., a chartplotter or autopilot is not receiving data

from a GPS).

Electronics (2)

P A R T

ELECTRICAL SYSTEMSTROUBLESHOOTING

W hen I first started cruising, we got by with oil lamps to read byand no AC shore-power system at all. The DC system providedpower for some cabin lights, the navigation lights, engine start-

ing, and an AM/FM radio (with a cassette player), and a basic electronicspackage consisting of a Loran-C, depth sounder, speed log, and VHF radio.None of this equipment was interfaced, so an onboard network wasn’t even adream at the time. But we got by just fine with that equipment and a goodselection of nautical charts, dividers and parallel rulers, and a watch.

Those days are gone, and so too are boats set up so simply. Today, boatbuyers’ expectations are driving more and more complexity into the installedsystems. Along with this trend the need has risen to develop new ways to seekout and troubleshoot problems. Why? Because boatyard labor rates have alsoincreased to the point where, as of this writing, $100-per-hour labor rates foryard services are the norm, and in some places the rates are even higher. Deliv-ering the maximum value for these labor rates is a basic expectation amongconsumers. They expect things to be done right the first time, and in theshortest amount of time possible.

So in Part 1, we’ll look at a variety of gear designed to speed up the diag-nostic process and to effectively diagnose equipment that can’t be tested usingtraditional test procedures (such as sealed batteries).

1


C H A P T E R

2Testing Batteries,Charging Systems, andStarter Circuits, andMeasuring Voltage Drop

Of all the areas marine electricians or boatowners must deal with, batteries, alterna-tors, and starter motors, along with their related circuitry, are among the mostcritical. Boats rely heavily on the integrity of their DC electrical system; on most

boats, if the batteries go dead, you’re simply out of luck—you can’t walk home!The electrical system is one area where our automotive counterparts have the advan-

tage. You bring your car into the repair shop, and the technician hooks it up to a diagnos-tic center. This electronic masterpiece produces all kinds of useful data, everything fromwhich cylinder is misfiring to the amount of poisonous emissions coming out yourtailpipe. It will also evaluate the performance of your battery, charging system, and startermotor circuits.

Unfortunately, it’s impossible to drive your boat into the diagnostic bay at your localauto shop and get the same sort of checkup. But let’s face it—most boatowners todayexpect this same level of efficiency and technical capability. After all, if they can get it fortheir $40,000 Lexus, why not their $400,000 Sabre sloop?

CATALYSTS FOR CHANGE

Enter the microprocessor. As we all know, microprocessors are continually becomingsmaller and more powerful. With these improvements have come changes in instrumenttechnology that are closing the gap between marine and automotive technicians. Instru-ment manufacturers today can produce smaller diagnostic equipment with increased func-tionality, and at prices that many boatowners and marine technicians can afford, or—inthe case of the pros—cannot afford to be without.

In addition, advances in battery technology have driven the development and modifi-cation of testing instruments. In the old days, we removed the caps from the battery cellsand visually inspected the fluid level of each cell. Then—if we had the tools—we used ahydrometer to measure the specific gravity and determine each cell’s state of charge, and a


1 5

carbon pile load tester to determine the bat-tery’s ability to supply amperage. Or if we didn’town a carbon pile load tester, we used avoltmeter and checked the voltage across thebattery posts while cranking the engine orrunning the anchor windlass.

These days, however, the vast majority ofboats have sealed batteries. These may beeither liquid electrolyte batteries or gel-cellsand absorbed glass mat (AGM) batteries(referred to as immobilized electrolyte batteriesby the ABYC). Either way, a hydrometer is ofno use because there’s no cap to remove. Andwhile a voltmeter will safely determine thebattery’s state of charge, it won’t tell you any-thing about the battery’s ability to deliveramps. Neither will it tell you which cell is bad.But that makes little difference because youcan’t replace individual cells. One bad cellmeans you have to replace the battery.

Additionally, load tests on sealed batteriesare extremely dangerous. Although they arereferred to as sealed batteries, they are moreaccurately termed sealed valve regulated (SVR)batteries. This means that the battery can ventitself if it develops excessive internal pressure—for example, due to an overcharging condi-tion. If this condition goes unchecked, theelectrolyte level will eventually fall belowthe tops of the battery plates, which can causethe battery plates to short-circuit. Conductinga load test on a battery under these circum-stances can produce an electrical arc inside thebattery case, which now has, as a result of theovercharging, a hydrogen-rich atmosphere.The result? Your battery explodes!

But even if you could use a battery loadtester, would you want to? The typical modelis heavy and cumbersome to get down into thebattery compartments on many boats. It’s somuch easier to use a handheld device.

Safety, value, functionality, and conve-nience—all are sound reasons for using the

testing batteries , charging systems, and starter circuits

CONDUCTANCE AND IMPEDANCE

Conductance is a measure of the ability of a battery to carrycurrent. It is the inverse of impedance, which is a battery’sinternal resistance. As a battery ages, its internal electricalresistance increases due to sulfate coating on its plates andgeneral deterioration. The result is that impedance increasesand conductance decreases.

If you know your battery’s original specifications, youcan program them into a battery conductance tester todetermine the battery’s state of health.

new, alternative instruments and methods thathave been developed for battery testing.

CONDUCTANCE BATTERYTESTER

Several years ago, in preparation for an articlefor Professional Boatbuilder magazine, I re-searched a new breed of conductance batterytesters. At the time, I was concerned about themisconceptions and tales of woe I was hearingregarding these instruments, yet I was alsointrigued by the possibility that they could bemore accurate than traditional battery testingmethods. I had only superficial experiencewith them and had never looked at how theyworked. The research was eye opening. Sincethen I’ve learned a lot about these devices andhave come to believe in their capabilities.

A conductance battery tester is easy and safeto use. No load is placed on the battery, butrather the tester sends low-level, pulsating volt-age through the battery from the positive tonegative post. By timing this low-level signal,the tester’s microprocessor determines the inter-nal resistance, translates that into conductance,and calculates the condition of the battery basedon the user-programmed specifications for thebattery. This is all accomplished in a matter ofseconds, and generally the battery does not

need to be recharged before conducting the test(a prerequisite for traditional load testing andspecific gravity tests with a hydrometer).

Conductance battery testers, such as thoselisted in the sidebar, eliminate the need forhydrometers and high-current-draw loadtesters. They are the only safe means of deter-mining the condition of sealed batteries. Whenselecting a conductance battery tester, considerthe types of batteries it can effectively analyze(e.g., flooded cells, gel-cells, AGM) and themaximum battery rating in cold cranking

1 6 electrical systems troubleshooting

amps (CCA). Also be sure that the testermatches the battery’s capacity. Marine batteriesoften have a larger capacity than automotivebatteries (an 8D-sized battery, for example),which some automotive testers cannot handle.

Midtronics is one of the leading compa-nies involved in the development of theseinstruments; I use a Midtronics Micro500XLconductance tester, which costs about $800,and have found it to be reliable. It has anamperage rating that accommodates 8D-sizedbatteries, which are common to the marine

Micro500XL, Midtronics, www.midtronics.comDBA Analyzer, Newmar Power, www.newmarpower.comBAT 121, Bosch, www.boschautoparts.co.ukCRT-300, Alber, www.alber.comAccuracy Plus, OTC, www.otctools.comYA2624, Snap-on, www.snapon.com

CONDUCTANCE BATTERY TESTERS

To measure conductance, a tester sends a small signalthrough the battery, then measures a portion of the pulsedcurrent response. This measures the plate surface avail-able in the battery, which determines how much powerthe battery can supply.

conductancetester

impressedvoltage signal

currentresponse

signal

+ –

clamps connectto battery

menu

digital readout

scroll upand downentercode

printer

The Midtronics Micro500XL analyzer with IR-linkedprinter.

industry. In addition, the unit’s long cables—alittle more than 10 feet (3 m) in length—haveproven quite handy for accessing hard-to-reach batteries. The instrument is versatile,and can also be used for testing starter circuitsand charging systems. (All three capabilitieswill be covered in this chapter.)

The menus on the tester’s LCD screenprompt you through the test sequence, and oncethe testing is done, you can transfer the data viaan infrared link to a mini printer. This is handyif you are a professional technician as you cancreate a report specific to your customer, includ-ing your company name and contact informa-tion (all user programmable). This printedrecord is just one more step toward the type ofprofessionalism boaters have come to expect.

Battery Test

You can learn how to use a conductance bat-tery tester in just a few minutes. To perform

1 7testing batteries , charging systems, and starter circuits

this test, be sure the battery is connected tothe boat’s electrical system. If your boat has amultiple battery configuration, test each bat-tery separately (see illustration).

In the photo sequence that follows, thetester is connected to the battery on a boat,and the complete test sequence is shown.

DC –

DC +

battery

switch open

panel-board

fuse

battery

sub-main

breaker

fused equipment

Micro500

low-level pulsating voltage to determine internal resistance

Leave battery connected to boat’s electrical system, but testeach battery separately. USE SWITCH TO SELECT BATTERY.

Connect the meter’s red clamp to the battery’s positiveterminal and the black clamp to the negative terminal.You can isolate multiple battery setups by using the bat-tery selector switch installed on the boat. For really largebattery banks (with more than two batteries), isolate thebatteries by disconnecting the positive lead from eachbattery you are testing in the system to ensure that theMicro500XL is collecting data for just the one batteryand not averaging its readings for several batteries.

Wiggle the clamps attached to the battery terminals toensure a tight connection. These meters are extremely sen-sitive and require a good connection. The Micro500XLwill prompt you to do this if it senses a loose or low-qualityconnection.

The meter has identified a loose connection to the nega-tive battery post clamp. Wiggle the clamp and retest.

2

1


The test indicates that the battery’s open-circuit voltage is11.77 V. This is less than 25% of a full charge, as indi-cated in the graph.

12.6

12.4

12.2

12.0

11.8

11.6

11.4

11.20% 25% 50% 75% 100%

voltage

Volta

ge

% Charge

Correlation Between % Charge and Open-Circuit Voltage

The graph shows the correlation between open-circuitvoltage and battery state of charge.

First identify the location of the battery: is the battery in orout of the vehicle (or in this case, the boat)?

Select the type of battery: flooded or AGM. For gel-cells,select “regular” for the best results. (In this case, “flooded”is synonymous with “regular.”)

Use the scroll keys to select the battery’s rating standard.The typical choices are CCA (cold cranking amps), CA(cranking amps), MCA (marine cranking amps), or DIN(Deutsches Institut für Normung, a German industrial stan-dard). Other options may be JIS (Japanese IndustrialStandard) and amp-hours (Ah).

Adjust the numerical amperage value to match the batteryrating. (This rating should be on the battery label.)

3

6

7

5

4

8


Starter Circuit Test

The Micro500XL can perform a completestarter circuit test, including measuring forminimum cranking voltage. Attach the red andblack leads to the cranking battery as you didfor the battery test (red to positive and black tonegative), then follow the meter’s instructions(see photos page 20).

Note that the cranking voltage test is onlyone of several tests that can be used to trou-bleshoot starter circuit problems. Current drawtests and voltage drop tests are also frequentlyused. We’ll look at how these are done usinganother high-tech tester later in this chapter.

A typical battery label showing CCA and MCA ratings.

The meter displays the battery’s state of health in graphform. A reading of less than 80% indicates you shouldreplace the battery fairly soon; at 60% or below, youshould replace it immediately. In this case, the situationlooks grim, since the battery is barely giving a reading.

The meter displays the state-of-charge (SOC) test, the resultsof the CCA test, and the battery’s CCA rating. In this exam-ple, the 600 CCA battery tested at 149 CCA, with a state ofcharge of 11.78 V. Based on these results, the unit’s recom-mendation is to “charge & retest” the battery (top of screen).(Note: In some test situations, the battery being tested mayhave such a low state of charge that the results will beskewed, confusing the battery tester’s microprocessor. In thiscase, the unit’s recommendation will be “charge & retest.”)

At the end of the test, the unit can generate and print a report.Make sure that you disconnect the battery before printing.

9

10 11

12


Charging System Test

The Micro500XL can perform several impor-tant charging system tests, as shown in the fol-lowing photo sequence. As you will see, theunit instructs you at each step. (As with thestarter circuit test, if you are testing an olderdiesel engine in cold temperatures, first warmup the engine for 5 minutes.)

Trend Analysis

One way to use the Micro500XL is to predictwhen a battery is going to give up the ghost. Youmay remember that in photo 11 on page 19,the screen display showed the rated CCA andthe measured CCA in real time based on the

MINIMUM CRANKING VOLTAGEAND VOLTAGE SPIKES

Minimum cranking voltage is especially important ontoday’s modern boats. The computer-driven systems foundaboard virtually all boats, as well as common marine elec-tronic equipment such as fishfinders and GPS chartplotters,are all sensitive to the low-voltage conditions that canoccur during engine cranking. In fact, low voltage duringcranking affects any system that shares the same battery(s)as the starter.

What is the minimum? Most modern engine manufac-turers recommend nothing less than 10.5 VDC. In mostcases, voltage levels below 10.5 VDC will increase thepossibility of an onboard computer “blinking out” or losingdata, as well as cause a variety of engine symptoms, suchas excessively rich fuel mixtures, rough running, or a com-plete failure to start. Symptoms will manifest differently fromone engine or system to another, but suffice it to say thatcranking voltage is of more concern now than ever.

High voltage spikes are also a concern, and are some-times caused by solenoids for battery combiner systemsand the like due to inductance (a property of a conductoror coil that determines how much voltage will be induced init by a change in current) as these devices open and closecircuits. This problem is dealt with most effectively by electri-cally isolating electronic navigation circuitry from crankingmotor circuits, which is often done by using a completelyseparate battery supply for the electronic equipment.

The initial screen for the starter circuit test: first, start theengine. (Note: If you’re testing an older diesel engine incold temperatures, warm up the engine for 5 minutesbefore beginning this test to prevent inaccurate results.)

This next screen shows the results. In this case, the startercircuit in question brought the system voltage down to10.89 V, a normal and acceptable condition. (Anythingless than 10.5 V on a computer-controlled engine is con-sidered unacceptable. On older engines without com-puter controls, a minimum of 9.6 V is acceptable.)

Press the ENTER key on the face of the instrument to beginthe charging system test.

1

21


Turn off all electrical loads and rev the engine for 5 seconds.The unit provides a screen view to ensure that engine rpm isdetected. It then advances to a horizontal tachometer-typedisplay. Bring the engine rpm to the level of the vertical lineand hold.

Now turn on electrical loads. Select critical, commonly usedDC loads that you may need or use simultaneously with theengine running; for example, navigation lights, bilge pumpand blower circuits, all navigation and communicationsequipment, and refrigeration systems. You want to be certainthat the system can supply all these circuits and have ade-quate power left to recharge the batteries at the same time.

The rpm scale for the loaded running test. Rev the engineto the vertical line and hold.

With loads on, idle the engine.

After idling, rev the engine again to the vertical line. Thisscreen shot shows the engine is just below the correct rpm.

The diode/ripple test measures AC voltage leakage pastthe rectifier assembly in the alternator. This test can indi-cate imminent charging system failure, or an electrically“noisy” alternator that can affect the performance of someonboard marine electronic equipment. This test is simply ago, no-go test——pass/fail. It can be performed separatelywith a digital multimeter set to the AC volts scale (anythingin excess of 0.4 VAC is considered excessive).

4 5

6

7

32

results of the battery condition tests. This infor-mation has more value than you might think,but it requires a bit of prior recordkeeping onyour part.

When you install a new battery, perform aconductance test on the first day of the battery’sservice life and log the CCA. This measurementwill be your starting point, or benchmark.Then periodically test the battery and log theresults. Generally, batteries don’t fail suddenly,but deteriorate gradually. As your battery ages,


your log entries will show a gradual decrease inavailable CCA. By tracking the CCA lost overtime, you will establish a trend based on yourboat’s actual use. This will enable you to makean educated guess as to when battery failure isimminent. The magic number is easy toremember—look for 80% of the battery’srated CCA value. (This is not an arbitraryvalue; it is based on standards established bythe Institute of Electrical and ElectronicsEngineers, IEEE.) At that point, it’s time toreplace the battery if you want to ensure itscontinued reliability.

DIAGNOSTIC METER

Although clearly an automotive-based instru-ment, a diagnostic meter is easily adapted tomarine uses and provides added functionalityand increased accuracy over a battery conduc-tance tester. The Midtronics inTELLECTEXP-1000, which costs about $1,100, hasfunctions for battery, starter circuit, and alter-nator testing, as well as capabilities for voltagedrop testing. (As of this writing—2007—Iknow of no other units with voltage drop test-ing capability via conductance testing.) Withthe inTELLECT EXP-1000, you can isolatecircuit faults caused by loose, corroded con-nections or undersized wiring—two commonproblems on boats—and it can also functionas a multimeter.

Features of the inTELLECT EXP include:

• Comprehensive battery tests, with animproved algorithm (compared to theMicro500XL) for more accurate tests ondeep-cycle batteries as well as AGMs andgel-cells.

• Capability to create performance graphsfor such things as starter current draw andalternator output. These features can beextremely useful in analyzing marginalperformance situations.

At the end of the charging system test, the Micro500XLprovides an overall analysis of the charging system. In thisexample, the system is normal.

This screen displays the actual voltage for the loaded andunloaded tests. As you can see, the voltage reading in theunloaded test is higher (by 0.13 V) than the voltage at thebattery terminals with the engine turned off. This differencejust means the charging system is doing something. How-ever, if the unloaded voltage is more than 2.5 V abovethe initial battery reading with the engine off, then the volt-age regulator is at fault. If the loaded voltage is less than0.5 volt above the static battery voltage, the alternator’samperage capacity is too small for the loads it is serving.

8

9

• A simple cable voltage drop test, performedby attaching the leads to each end of anycircuit. It will definitively isolate excessivevoltage drop to either the power feed orground return side of the circuit. This saveshaving to check each side of the circuit sep-arately using a conventional multimeter,and will provide a pass/fail answer based onuser-programmable parameters enteredinto the meter before testing begins.

• Full digital multimeter capabilities,including DC volts, AC volts, amperage(with the optional amp clamp), tempera-ture, ohms, and test diodes. It also pro-vides a small oscilloscope.

• Battery-operated printer connected to theunit via an infrared link. This lets youprint full test results as a record for cus-tomers or as backup to a work order forfuture reference.

As described in my book Powerboater’sGuide to Electrical Systems, voltage drop tests pre-viously required that the circuit in question beactivated and that at least some current beallowed to flow through it. This can be some-what of a handicap on circuits that have simplystopped working. The inTELLECT EXP-1000provides its own low-level power to the circuit toenable its conductance testing capabilities, mak-ing it possible to determine if excessive voltagedrop exists without having a live circuit. Further,the inTELLECT EXP-1000 will automaticallydetermine the exact voltage drop in volts, andisolate whether the excessive drop is on thepower (supply) side or the negative (return) sideof the circuit. This saves considerable time overthe traditional methods used to determine thelocation of excessive voltage drop in a circuit.

Battery Test

The inTELLECT EXP represents the latest evo-lution in the Midtronics line of battery testers.Like the Micro500XL, it uses conductance


The inTELLECT EXP-1000 has a large screen display, analphanumeric keypad, and a number of unique capabilities.

The main menu of the inTELLECT EXP-1000.


First, you enter some basic information, such as whetherthe battery is in or out of the “vehicle.”

Then you enter the type of battery connection: top post, sidepost, or “remote.” This last option accommodates testingfrom the “jump start” terminals now incorporated on someover-the-road vehicles, and even some new boats. You canuse this option to hook into the positive and negative DCbus bars found behind most boat electrical panels, eliminat-ing the need to crawl into some tight battery installation. Bat-teries connected in series or in parallel should be tested inisolation from one another, however, so unless it’s possibleto isolate the batteries by switching, the remote connectionoption may not be practical. The unit’s red lead goes to thebattery positive terminal; the black lead to the negative.

Next, you enter the battery type: regular flooded, AGM,AGM spiral wound (such as the Optima brand), or gel-cell.

Then you enter the battery capacity rating standard shownon the battery label. Eight choices are provided (four areshown), covering all world standards for battery ratings.

inTELLECT EXP-1000, Midtronics, www.midtronics.com

FULL-FEATURE DIAGNOSTIC METER

1

2

3

4

technology to determine battery condition, onlywith a more sophisticated algorithm pro-grammed to its internal microprocessor. Thissubtle improvement allows the tester to more


accurately diagnose problems with all threecommon battery types: flooded (liquid elec-trolyte), gel-cells, and AGMs. The photosequence shows the battery test procedure.

If conditions are outside of the parameters—such as low temperature or deeply discharged—required for an accurate test, one of several screentests may appear next:

• Temperature compensation test: TheinTELLECT EXP-1000 may ask you tomeasure the battery’s temperature with theunit’s infrared temperature sensor if theunit detects that the temperature maymake a difference in the result. It willprompt you to place the sensor within 2inches (50 mm) of either the top or side ofthe battery. After the temperature readingis displayed, hit the “Next” key. Theinstrument will capture the temperaturedata and recalculate its findings.

• Deep scan test: If temperature compensa-tion doesn’t allow the in TELLECT EXP-1000 to complete its calculations, the unitwill jump to a deep scan test to furtheranalyze the battery. It may ask you to run a

Then you enter a specific rating value. In the case of CCAor MCA, the entry range is from 100 to 3,000 amps. Thisrepresents more than enough capacity to deal with eventhe largest marine battery in common use, the 8D, whichhas a CCA rating between about 1,200 and 1,600amps, depending on the make and model. After enteringthe required data, press “Next” and the test begins.

The results of the battery condition test: Good Battery. At12.48 V, the battery is not fully charged, but because itsindicated capacity of 543 CCA is over its rated capacity,the battery is still in good condition.

The SOC screen presents battery voltage from photo 6in an easily comprehended graphic format. In this case, ittells you that 12.48 V is 75% SOC.

5

6

7

5-minute discharged battery test, eitherbefore or after recharging the battery.

At the end of the testing, the inTELLECTEXP-1000 displays one of five test result mes-sages: good battery; good but recharge; chargeand retest; replace battery; bad cell—replace.Depending upon the results, numerical valuesare displayed, as are two screens showing bat-tery state of charge (SOC) and state of health.These last two screens are user selectable.

Starter Circuit Test

If you initially chose “system test” from themain menu, the inTELLECT EXP-1000 will


move automatically to the next test—thestarter circuit test.

To get the most comprehensive results,you will need the optional amp clamp. Placethe clamp around the main starter battery feedcable to measure the amperage the starter isdrawing while it is cranking. This is an impor-tant part of overall starting system analysis.Assuming that the engine isn’t seized, an exces-sively high amperage draw indicates a possiblefault inside the starter motor. An excessivelylow amperage draw indicates a faulty connec-tion to the starter, which could be caused byeither a loose or corroded connection orcabling that is too small for the job.

While the inTELLECT EXP-1000’soptional clamp is recommended, be aware

Decision Recommended Action

GOOD BATTERY Return the battery to service.GOOD—RECHARGE Fully charge the battery and return

it to service.CHARGE & RETEST* Fully charge the battery and retest.

Failure to fully charge thebattery before retesting maycause false readings. IfCHARGE & RETEST appearsagain after you fully charge thebattery, replace the battery.

REPLACE BATTERY Replace the battery and retest. AREPLACE BATTERY result may alsomean a poor connection betweenthe battery cables and the battery.After disconnecting the batterycables, retest the battery using theout-of-vehicle test before replacing it.

BAD CELL—REPLACE** Replace the battery and retest.

*If the result is CHARGE & RETEST, the EXP will calculate and dis-play the time needed to charge the battery at 10, 20, and 40 A.** When testing at the remote posts, the EXP may need to verify theresult. It will give you the option of retesting at the battery posts.

Source: Midtronics

Battery Decisionsand Recommendations

TABLE

2-1

Finally, the meter displays a state of health (SOH) screen, asummary based on the measured CCA versus the pro-grammed or rated CCA. In this case, the meter “dial” showsthe pointer between 50% and 100%, indicating approxi-mately 70% to 75% state of health. This battery will need tobe replaced fairly soon. The magic number to remember is80% of the rated CCA. Virtually every battery I’ve evertested using a conductance tester will measure more than itsrating when fairly new. Once a battery measures less than80% of its rating, it should be replaced. It’s important not toconfuse state of charge with state of health: SOC is merely areading of the open-circuit voltage across the battery’s termi-nals, but really doesn’t provide any information about thebattery’s ability to deliver current as SOH does.

8

that its measurement range (up to 700 amps)is not enough to capture starter current drawon some modern medium and large marinediesel engines. If you frequently work withsuch engines, you might want to invest in astand-alone amp clamp with a range up to1,000 amps DC. (If you are not using theinTELLECT EXP-1000’s clamp, select “notavailable” during the initial test setup.)

First, the inTELLECT EXP-1000 verifiesthe battery condition (described above in theBattery Test section) as a prerequisite to anystarter circuit test. Once a good battery hasbeen confirmed, completing the test proce-dure is simply a matter of starting the engine.Use the same, simple two-wire positive andnegative connections at the battery already inplace and connect the optional amp clamparound the battery negative cable.

With these in place, the inTELLECT EXP-1000 will measure and record the following:

• average cranking voltage• cranking amperage (if you use the

optional amp clamp) • cranking time in milliseconds• starter loop resistance (in ohms); note

that this test will only be useful if you


Decision Action

CRANKING NORMAL The starter voltage is normal andthe battery is fully charged.

LOW VOLTAGE The starter voltage is low and thebattery is fully charged.

CHARGE BATTERY The starter voltage is low and thebattery is discharged. Fully chargethe battery and repeat the startersystem test.

REPLACE BATTERY (If the battery test result wasREPLACE or BAD CELL.) The bat-tery must be replaced before test-ing the starter.

LOW CRANKING The starter voltage is high but theAMPS cranking amps are low.

NO START The engine didn’t start and the testwas aborted.

CRANKING SKIPPED The EXP didn’t detect the vehicle’sstarting profile and skipped theStarter Test.

Source: Midtronics

Starter System Decisions andRecommendations

TABLE

2-2

Results of the cranking motor test, showing voltage, amps,and cranking time. (With an attached amp clamp, this screenwould also display the starter loop resistance reading.)

The voltage reading during the cranking cycle.

have previously established a baseline forthe circuit, as with cranking amps

Normal figures for older, noncomputer-ized engines must provide a reading of over9.6 V while cranking. Modern engines shouldalways read in excess of 10.5 V.

Interpreting the ResultsVoltage and amperage readings can tell youmany things beyond whether the starter cir-cuit is in order. Particularly on modern boats,which are increasingly powered by electronicallycontrolled engines, excessive system voltagedrop during engine cranking is a concern. Forexample, assuming the connected battery hastested OK, voltage readings that are lowerthan desirable may indicate that the battery istoo small (i.e., not enough capacity) for thetask at hand, or that the wiring is too small forthe job and an upgrade is required.

Cranking amperage is also of concern, asmentioned above, but historically, enginemanufacturers have been more than a little shyabout sharing relevant cranking amp specifica-tions with technicians or end users of theirproducts. In the old days, 1 amp per cubicinch of engine displacement was the roughrule of thumb, but this applied only to gaso-line engines. Diesel engines, with their muchhigher compression ratios, often pulled farmore than 1 amp per cubic inch.

Starter motor technology has changed, too.The 1 amp figure was reasonable for old-stylefield-wound motors, which characteristically pullmore amperage. But with the evolution to perma-nent magnet–type motors, gear reduction motors,and such, starter current draws have decreaseddramatically in the last ten to fifteen years.

Therefore, as with other measurements,starter current draw as a diagnostic tool is onlyas good as the information you start with. Doyou know what the draw is supposed to be? Ifyou are working on the same systems repeatedly,


or the starter in question is on your own boat,establish a benchmark when everything is func-tioning normally. Log this number and the tem-perature at which the value was measured forfuture reference. Remember, cold temperatureswill increase the load on the starter and cause themotor to pull more amperage. Typical draws formodern starter circuits range anywhere from150 to 850 amps at 80°F (27°C). At 80°F, anyvariation from the norm that exceeds about±10% to 20% indicates a problem.

Higher than normal current draw could indi-cate a seized engine, although this should havebeen ruled out already. (Remember, you are prob-ably performing these tests to establish the causefor slow engine cranking. A partially seized engineis generally the result of an extreme overheatingincident, in which case the temperature gaugewould have registered over 215°F (102°C). Thevessel’s history and other symptoms will usuallyconfirm or deny this possibility.) Assuming theengine is in good condition, higher than normalcurrent draw is probably a problem internal tothe starter motor. Remove the starter for furtherinspection and repair as needed.

Lower than normal current draw is a classicsymptom of loose or corroded cable connectionsor undersized wiring (which will show on theinTELLECT EXP-1000 as higher than normalloop ohms resistance). You may need to conductadditional testing to determine the location ofthe excessive resistance within the circuit. If thewiring checks out OK, then the problem iswithin the motor itself.

Charging System Test

The third test under the System Test (mainmenu) is the charging system test. As with theother tests, it is easy to perform by followingthe unit’s on-screen prompts. The cable con-nections are the same as for the battery andstarter tests, with the possible addition of theamp clamp. (If you are following the meter’ssystem test procedure, advance to the charging


system test by pressing the “Next” key afterthe starter circuit test is completed.)

AC ripple is the amount of AC leakage pastthe diodes in the alternator’s rectifier assembly,which indicates either alternator stator damageor, more likely, rectifier diode failure or very lowquality diodes. I generally use 0.4 VAC as themaximum acceptable reading. More than thatwill almost surely induce excessive RFI (radiofrequency interference), with the potential forinterfering with electronic systems on board.(Many of the worst cases of excessive AC rippleI’ve tested in the field were on newly rebuiltalternators, which says something about thequality of the diodes some remanufacturers use.)

For the next phase of the test, turn on electri-cal loads. The meter suggests automotive acces-sories such as headlights and the heater blowerfan, but you should switch on the critical loadsas defined in ABYC Standard E-11 for DCload calculations (see column A in the ABYCworksheet on page 30). Some typical DCamperage draw values for common onboardloads are shown in Table 2-3.

The sequence begins with the unit prompting you to turnoff all loads and idle the engine. If the unit senses a no-charge condition at idle (common to many diesels withself-exciting alternators), it may ask you to confirm whethera diesel is the subject of the test. (Some diesel enginesrequire the engine to be revved at above idle speed toexcite the alternator into producing a charge.)

Next the unit prompts you to rev the engine for 5 secondsto a certain rpm level (indicated by a hash mark) with noelectrical loads. The EXP-1000 will tell you when enginerpm is detected; at that point, hit the advance key on themeter to move to the data page, which will give the resultsof the test with loads off. Then it tests for problems, such asexcessive AC ripple, voltage output, and charging amper-age values if the amp clamp is used.

Equipment Load (amps)

Anchor light 1—3Bilge blower 1—8Bilge pump 2—8DC refrigeration 5—20Depth sounder 0.1—4Knotmeter 0.1—1GPS/chartplotter 0.1—5Masthead light 1—2Radar 4—8Running lights 3—6SSB radio 1—30 (30 in transmit mode)VHF radio 0.7—1.5Windshield wiper motors 1.5—5 (each)

DC Current DrawTABLE

2-3

1

2

The values given in Table 2-3 are approxi-mate, and actual current draw will vary basedon specific equipment. It’s always best to usean inductive amp clamp and create your ownlog of current draw for every circuit on a boat.This log can become a useful diagnostic aidwhen problems do arise.

Measuring current draw with an inductiveamp clamp is not too time consuming. Beforetesting any appliance for current draw, disconnectthe appliance from the boat circuitry and connectit directly to a good battery with a pair of jumper


cables. (The gauge of battery jumper cables isusually sufficient to carry all the needed currentand obtain valid readings.) Set the inductive ampclamp around the DC positive conductor tomeasure the current draw and log the value. Thiswill provide the benchmark value to effectivelyuse the inTELLECT once the appliance is recon-nected to the boat’s circuitry; if the inTELLECTindicates anything less than the benchmark value,there is excessive voltage drop in the circuitry.This could be due to a loose or corroded connec-tion or a wire that is too small for the job.

The electrical load requirement worksheet from ABYC Standard E-11.(Courtesy ABYC)


Turn on critical electrical loads as specified by ABYCStandard E-11, as shown in the worksheet opposite. Aftera few seconds the EXP will prompt you to rev the enginefor 5 seconds with the loads on. The correct rpm level willbe shown in a graphic display similar to that shown for theno-load test in photo 2 on page 29.

Next, turn off the loads and the engine.

The test results. In this case the system only lost 0.01 Vbetween the loaded and unloaded test, indicating that thealternator charging system had no problem keeping upwith the loads. The minimum to look for is 0.5 V more thanthe initial open-circuit voltage reading on the batterybefore the alternator is even operating (i.e., with theengine not running). The EXP-1000 will check this automat-ically; thus the screen displays “no problems.”

The arrow keys allow you to scroll through a series ofresults in bar graph format.

The results of the AC ripple test, showing peak-to-peak ACvoltage and a graph of the diode waveform.

3 4

5

6

7


Decision ActionNO PROBLEMS The system is showing normal output from the alternator. No problem detected.

NO OUTPUT The alternator is not providing charging current to the battery.• Check the belts to ensure the alternator is rotating with the engine running. Replace

broken or slipping belts and retest.• Check all connections to and from the alternator, especially the connection to the bat-

tery. If the connection is loose or heavily corroded, clean or replace the cable andretest.

• If the belts and connections are in good working condition, replace the alternator. (Oldervehicles [and modern boats with high-output alternators often] use external voltage regula-tors, which may require only replacement of the voltage regulator.)

LOW OUTPUT The alternator is not providing enough current to power the system’s electrical loads andcharge the battery.• Check the belts to ensure the alternator is rotating with the engine running. Replace

broken or slipping belts and retest.• Check the connections from the alternator to the battery. If the connection is loose or

heavily corroded, clean or replace the cable and retest.

HIGH OUTPUT The voltage output from the alternator to the battery exceeds the normal limits of a func-tioning regulator.• Check to ensure there are no loose connections and that the ground connection is nor-

mal. If there are no connection problems, replace the regulator. (Most alternators have abuilt-in regulator requiring you to replace the alternator. In older vehicles [and somemodern boats with high-output alternators] that use external regulators, you may need toreplace only the voltage regulator.

The regulator controls voltage ouput based on the battery voltage, underhood [or engineroom] temperature, and vehicle loads used. In other words, it controls the maximum voltagethe system can produce based on the current needs and amount of current that can be pro-duced by the spinning of the rotor in the alternator. The normal high limit of a typical automo-tive regulator is 14.5 volts �0.5. Refer to the manufacturer specifications for the current limit,which may vary by vehicle type.

A high charging rate will overcharge the battery and may decrease its life and causeit to fail. If the battery test decision is REPLACE and the charging system test shows aHIGH OUTPUT, check the battery’s electrolyte levels. A symptom of overcharging is bat-tery fluid spewing through the vent caps, which causes low electrolyte levels and willharm the battery.

EXCESSIVE RIPPLE One or more diodes in the alternator aren’t functioning or there’s stator damage, which isshown by an excessive amount of AC ripple current supplied to the battery.• Make sure the alternator mounting is sturdy and that the belts are in good shape, and function-

ing properly. If the mounting and belts are good, replace the alternator.

OPEN PHASE The EXP has detected an open phase within the alternator. Replace the alternator.

OPEN DIODE The EXP has detected an open diode within the alternator. Replace the alternator.

SHORTED DIODE The EXP has detected a shorted diode within the alternator. Replace the alternator.

Source: Midtronics

Alternator Decisions and RecommendationsTABLE

2-4

If you use the optional amp clamp, theunit will display alternator output in amps,both loaded and unloaded. This informationis useful for performing a load analysis. Thealternator’s job is to supply voltage to nor-mally running electrical equipment and haveat least 0.5 V left over to recharge the battery.An underrated (in amps) alternator will not beable to do this and will display less than the0.5 V increase over static voltage with loadsturned on. Again, you can perform this testwith a stand-alone amp clamp around eitherthe battery positive or negative cable.

Voltage Drop Test

I’ve been endorsing voltage drop as a way to pin-point weak links in an electrical circuit for years,but there is still a general lack of understandingof the procedure and its applications. Manytroubleshooters set their digital volt-ohmmeter(DVOM) to the ohms scale and check for con-tinuity at various points throughout a circuit.Others use a 12 V test light to see if there isenough potential at a given point in a circuit tolight the bulb. Neither of these approaches isreally adequate, however. An ohmmeter mayshow continuity, and even a measurable resist-ance value, but what does that tell you if youdon’t know what the resistance should be? Thebulb in the test light may glow, but is it glowingbrightly enough? Only by measuring voltagedrop can you really get a handle on the qualityof a circuit and all its termination points.

To measure voltage drop—i.e., how muchvoltage is “lost” in a circuit—there has to be atleast some current flow. At one time, this testcouldn’t be performed on an inactive circuit,but as noted earlier, the EXP generates its ownsignal, so this is no longer a problem.

Significance of Voltage DropKeeping in mind that conductance is the inverseof impedance (resistance), excessive voltage dropis caused by high electrical resistance. Too much


resistance (which is measurable) can cause a cir-cuit to perform poorly or not at all. ABYC Stan-dard E-11 identifies key circuits and the accept-able levels of voltage drop as a percentage ofnominal voltage. For critical circuits like elec-tronics, bilge blowers, panel feeders, and naviga-tion lights, the limit is 3% of the nominal circuitvoltage (generally either 12 or 24 V). For non-critical circuits, such as cabin fans and electricheads, the figure is 10%. These translate into thespecific voltage losses shown in Table 2-5.

These numbers represent the maximumamount of voltage we want to see “go missing”due to resistance in electrical circuitry, exclu-sive of the actual load in the circuit. (The lostvoltage actually turns up as heat, the primaryby-product of excessive electrical resistance.)These values, I believe, are part of the reasonwhy many electricians have trouble graspingthe significance of voltage drop: the numbersseem too small to worry about. But in fact,these small numbers have great significance.Losses in excess of these amounts are due toundersized wiring or loose or corroded termi-nation points—among the most commonproblems in DC marine systems. (We usuallydon’t worry too much about AC voltage dropon board because the wire runs in AC circuitsare generally too short to be a major factor.)

Using the inTELLECT EXP-1000The inTELLECT EXP-1000 generates a low-level signal and calculates the voltage drop overa given leg of the circuit or over the entire circuit,

System Critical Noncritical Voltage Circuits (3%) Circuits (10%)

12 O.36 V 1.2 V24 0.72 V 2.4 V

Acceptable DC Voltage Loss(per ABYC E-11)

TABLE

2-5

depending upon where you place the leads.The readout identifies the voltage drop in thepositive and negative sides of the circuit asseparate values, which should save you a lot of

time in narrowing down the exact location ofthe fault. (It’s usually at one end of the circuitor the other, or any terminal point inbetween.)


DC –

DC +battery

switch open

cabin light

– bus bar

fuse

inTELLECT EXP-1000

supplementary test leads (provided with meter)

+ bus bar

To calculate voltage drop, both of the inTELLECT EXP-1000’s lead sets are required. The battery test lead and the DMM(digital multimeter) lead have different plug ends, so you can’t connect them incorrectly at the meter. Each lead has one blackand one red end clamp for attachment to the circuit.

Attach the red lead from the DMM lead on the positive side at the circuit’s source of power, and the black lead tothe negative side. At the other end of the circuit, connect the red battery lead to the positive connection, and the blacklead to the negative connection.

After entering the amperage draw value for the circuit, hit the “Next” key. The device will test the circuit and displaytotal circuit voltage drop. It will also display individual values for both the positive and negative return sides of the circuit,saving several steps compared to the use of a traditional multimeter.

DC –

+ bus bar

battery

switch closed

cabin light

– bus bar

fuse

DMM or DVOM

fuse

DMM or DVOM

Using a conventional meter, you have to connect, disconnect, and reconnect both ends of the circuit to acquire the samedata. Then you would still have to perform some calculations to get voltage drop.

1

2

Limitations of the inTELLECTEXP-1000Despite the inTELLECT EXP-1000’s tremen-dous capabilities, it does have some minorlimitations:

1 You are limited by cable length. Thelength of circuit you can test is onlyabout 18 feet (5.5 m), which is the com-bined length of the unit’s two cables.Midtronics states that extending thecables can result in a loss of signalstrength, which might affect the micro-processor algorithms. Happily, 18 feet issufficient for most circuits.

2 You must know the circuit’s amperage.The EXP requires you to enter the cir-cuit’s amperage value. Acquiring theamperage value for a given circuit meansyou have to know the current rating for aparticular appliance in the circuit. Lookfor the rating on a plate on the appliance


or in the manufacturer’s installation man-ual or specification sheet.

Note: It’s a good idea to log this infor-mation and update it when you add orswap a piece of AC or DC equipment.You’ll be prepared for future circuittroubleshooting.

3 If the correct current draw is not known,some preliminary work is needed to makesure the inTELLECT is programmed forthe correct amperage (see page 30).

VALUE AND UTILITY

In addition to all the above-mentioned func-tions, the inTELLECT EXP-1000 can also actas a simple multimeter for general electricalwork around the boat—a handy feature,although hardly enough on its own to justifythe investment in this type of instrument.

In my opinion, the inTELLECT EXP-1000 provides more functionality than theMicro500XL. Although the Micro500XL per-forms a good battery test, it may not be as pre-cise in its evaluation of very large (8D-sized)AGM and gel-cell batteries. Additionally, theinTELLECT EXP-1000’s voltage drop testingcapabilities are a major breakthrough.

The typical boatowner would be servedwell by the Micro500XL, but for the advancedprofessional technician, I strongly recommendthe inTELLECT EXP-1000. It can generateuseful troubleshooting data more readily thanany other method. It may, however, give theaverage boatowner more information than heor she needs.

Although I am not aware of other devicessimilar to the inTELLECT EXP-1000, con-ductance battery testers comparable to theMicro500XL are available from a number ofsources, including Snap-on and OTC (seepage 16). The offerings of these and othercompanies may be of equal utility and value,

The results screen for a tested circuit. It shows the total volt-age drop and the separate drops on the positive (0.04 V)and negative (0.11 V) sides of the circuit. These are typicallow-voltage readings and well below the 3% maximumvalue you should see at the main power supply circuit.

3

but I believe you will benefit from seeing thecapabilities of the specific models shown hereas these types of instruments are not yetwidely known.

The equipment discussed in this chapter isnot cheap; indeed, these items may be amongthe most expensive test equipment in yourshop. But when you consider that twenty-fiveyears ago a professional technician might havepaid a similar amount for a high-end carbonpile load tester that only tested batteries, you


can easily justify the cost in terms of function-ality, safety, and payoff potential.

Keep in mind that this field is developingrapidly, and we should expect numerousimprovements, new functionalities, and newmodels and suppliers on a regular basis. Whenyou’re ready to buy, take a thorough look atwhat the market offers and, if you want toremain at the cutting edge as a top-notch tech-nician or thoroughly capable boatowner, buythe best you can afford.

Testing Continuity andTracing Circuits

Two of the most time-consuming tasks for marine troubleshooters are findingbreaks in long circuits and tracing wires through tangled bundles and harnessesthat snake in and out of view as they pass through bulkheads and behind cabi-

netry. Tone-generating circuit tracers and time domain reflectometers (TDRs) are twomodern tools that greatly simplify these tasks.

Like many of the tools in this book, tone-generating circuit tracers and TDRs have beenused for years in other industries, such as IT and telecommunications, before being “discov-ered” relatively recently by high-end marine electrical technicians. Few marine technicians,and far fewer private boatowners, have heard of or used these very useful tools.

Without these tools, however, troubleshooters must struggle with a multimeter orDVOM set to the ohms scale, and run continuity checks one wire at a time. This ofteninvolves dragging an extended connection lead through the boat to attach both ends of themeter leads to the wire or harness. And even if the continuity test does confirm a break inthe circuit, you are still left wondering exactly where the break is located.

TDRs and circuit tracers eliminate all that work. When connected to one end of a pairof conductors (and it must be a pair), both devices bounce a signal between the two con-ductors. When the “bouncing” stops, a fault is indicated. But the similarities end there.

Working from one end of the conductor, a TDR can also identify exactly how fardown the wire run a problem is located. (Amazingly, TDRs have an effective range of6,000 feet/1,829 m—well beyond the distance needs on boats.) Tone-generating circuittracers, in contrast, require access to the entire length of the wire. You connect the trans-mitter to one end of the conductors, then trace along the wire with the handheld receiverunit. As long as the receiver sounds off, it is receiving a signal, indicating continuity. Whenthe noise stops, you’ve found your break.

If access is not a problem, a tone-generating circuit tracer may be easier to use, since itshows you the exact location of the fault. If access is a problem, a TDR may more usefulsince it tells you where the fault is located, as a function of distance from the device. Youthen have to find the location, perhaps using a tape measure.

Pricing is another major difference. Unlike many of the other tools discussed in thisbook, tone-generating circuit tracers are an extremely modest investment, running in the

C H A P T E R

3


$60 to $100 range. TDRs, on the other hand,are not quite as basic. The alphanumeric unitdescribed in this chapter costs about $500.The time it can save in troubleshooting prob-lems, however, more than justifies its price.

Warning: You should trace only unener-gized wiring. Contact with live circuits canresult in severe injury or death. Always dis-connect power to the circuit before using acircuit tracer.


tracer (receiver)

signal-generating transmitter

Next we’ll look at how these tools are usedfor tracing wires through boats, finding opencircuits or breaks in wires, and in the case ofthe TDR, how far down a wire run the breakor short circuit is located.

TONE-GENERATINGCIRCUIT TRACER

A tone-generating circuit tracer has two com-ponents: a transmitter, and a handheld receiveror tracer. The transmitter, connected by its dualleads to a pair of cables routed together, sendsan oscillating signal down the length of one ofthe conductors. Most units operate in a fre-quency range between about 800 Hertz (Hz)and 1,100 Hz. This signal bounces, or reflects,off the parallel cable, something like radar. Thereceiver unit’s pointed end detects this reflectedsignal and amplifies it so that you can hear it.(Most units also have a small light built into thereceiver that glows as it senses the signal.) Bymoving the receiver down the length of a wirerun, you can effectively trace the signal acrossthe conductor’s entire length. If the receiversuddenly stops producing audible and visualsignals, an open circuit or break is implied.Right there you may have found the source ofyour electrical problem.

You must have access to the entire wire runand be able to track down the entire length ofthe harness to find a break. Unfortunately, you

The Wire Tracker tone-generating circuit tracer (left) is sold in the UnitedStates by Ancor Marine. It is really two devices: a signal-generatingtransmitter and a handheld tracer or receiver. The Fault Mapper modelCA7024 alphanumeric TDR (right) is made by AEMC Instruments.

Wire Tracker, Ancor Marine, www.ancorproducts.comFox and Hound, Triplett, www.triplett.comTR02 Cable Tester, AEMC, www.aemc.com

TONE-GENERATING CIRCUIT TRACERS

3 9testing continuity and tracing circuits

fuses bus bar

alligator clips

negativepositive

For this example, connect the transmitter at the sourceof a circuit on a small fuse panel. Clip the transmitter’sred lead to the output, or DC positive, side of the fuse,and clip the black lead to the terminal on the panel’sDC negative bus bar. Notice that both of these leadsare bundled together in a harness with four other wiresas they head away from the panel, so the signal gener-ated from the tool will be able to bounce off the leadsas the signal travels the length of the harness.

Follow the harness to another point in the boat. You’llknow the circuit is still intact because the tracer/receiver issending out a loud tone, and the light at the top of the toolcontinues to glow. If the light goes out and the soundstops, an open circuit is indicated. If you have or can gainaccess to the harness throughout its run, you can pinpointthe break by tracing back to the point where the tone andlight come back on.

will often not have that luxury on many instal-lations because many cable runs are routedthrough conduits or behind installed cabi-netry. That said, the device is useful for identi-fying which wires are which as they reappearat the opposite end of a hidden run, as long asthere are no breaks along the way.

The photo sequence illustrates the Ancortracker tool in use.

Note: The power must be turned off eitherat the DC main on the panel or at the batterymaster switch on the boat when using thistool; it can’t share power transmission and itsown signal.

Frequently a harness will disappear behind a panel or intoa conduit. At the opposite end, use the tone-generatingcircuit tracer to identify the conductor/pair you’ve beentracing. As long as the circuit has continuity up to thatpoint, the device will glow and sound off when you touchthe receiver unit against the correct wire.

1

3

2

ALPHANUMERIC TIMEDOMAIN REFLECTOMETER

The TDR has been around for some time.Widely used by the military, computer net-work technicians, and the telecommunicationsindustry, the technology is proven and acceptedas the most efficient way to trace problems inlong wire runs. Historically, these devices have


been expensive; at prices ranging from $5,000to $10,000, they were beyond the means ofalmost all marine electricians, and out of thequestion for boatowners. A few years ago, how-ever, costs dropped dramatically, and goodalphanumeric TDRs became available foraround $500. I immediately tested and subse-quently purchased one of these new-generationunits, and I’ll never go back to using an ohm-meter for tracing wire runs again. This tool isthe only way to go in today’s world.

Velocity of Propagation

A TDR needs to know the velocity of propaga-tion (VOP) of the wire being tested before itcan begin.

VOP is measured as a percentage of thespeed of light (186,000 miles per second or299,792,458 meters per second). A VOPvalue of 100% simply means that a cable couldconduct electricity at the speed of light. Butbecause all cable has some inherent resistance,the VOP value will always be less than 100%,meaning that the electricity is runningthrough the cable at a percentage of the speedof light. And as that percentage will vary withsize and type, the TDR must be calibrated forthe type of wire or cable you plan to test.

Although the AEMC Fault Mapper, thetool I use, contains a fairly comprehensivelibrary of VOP values for commonly used net-work and coaxial cabling, none of these comeclose to the values for commonly used marinewiring. Fortunately, this shortcoming is easilyovercome, as described below.

Fault Mapper CA7024, AEMC, www.aemc.comModel 3271, Triplett, www.triplett.com

TIME DOMAIN REFLECTOMETERS

faultTime Domain Reflectometry

transmittedpulse

reflectedpulse

origin

Distance =t1 + t2

2CO Vp

Co = speed of light in a vacuum

Vp = velocity of propagation

t2

t1

A TDR transmits pulses of a known shape and amplitude into one end of acable. The pulses travel along the cable at a speed determined by its VOP.As they reach impedance changes in the insulation of the cable, indicatinga fault or a cable end, the reflections caused travel back along the cableand are identified by the TDR. The size, shape, and general nature of thereflected pulses indicate the type of fault encountered. The distance to thefault can be determined from the time it takes for the pulse to be reflected.

Determining the VOP ValueFor this example, we are using the AEMCFault Mapper’s method to determine VOP,but the steps will be similar for other brands:

1 Cut a length of duplex conductor at least60 feet (18.5 m) long. Measure the lengthaccurately with a tape measure.

2 Connect the meter’s red lead to one of thetwo pieces of wire and the black lead tothe other (strip back the insulation onboth leads first). (Don’t twist the conduc-tors together at the far end or you’ll createa short circuit.)

3 Turn on the Fault Mapper, push the meter’stest button, and note the indicated length.

4 Use the scroll keys to adjust the VOPvalue up and down until the test resultequals the actual length of the cable. Yourfinal VOP value will be appropriate for allcables of the same gauge and type.

I’ve tested many cable types and gaugesand have found that all the cable commonlyinstalled in boats falls in the range of 60% to65% VOP. If you’re off by a percentage pointor so, it’s not the end of the world, but it willcreate a small inaccuracy in the meter’s calcu-lation of distance to the fault. Table 3-1 givesthe VOP values for commonly used AmericanWire Gauge (AWG) sizes of boat cable, alongwith metric equivalents.

Using the TDR to Locate a Fault

Before you can begin testing, you must deter-mine the size of the cable or wire you are test-ing. All approved wire and cabling has its sizeprinted on its insulation jacket (in AWG inNorth America; in mm2 for the rest of theworld) as in the top photo.

Once you know the wire size, follow thesesteps:


AWG Metric Equivalent (mm2) VOP (%)

8 8 6310 5 6412 3 6214 2 6116 1 61

Velocity of Propagation Values forTypical DC Boat Wiring

TABLE

3-1

This wire’s size——4.0 mm2——is printed on its insulationjacket. This is roughly equivalent to 10 to 12 AWG.

fuses negative

positive

busbar

Attach the meter’s leads to the small fuse panel at the source of the testcircuit: the red lead goes to the DC positive source at the fuse, and theblack lead to the DC negative. (Anywhere on this bus will do, as it is acommon return for all the circuits on the panel.) The TDR screen displaysa VOP value of 61%, which corresponds to the circuit’s 14 AWG wire.The meter’s internal battery status (fully charged) is also shown graphi-cally at the bottom of the display.

1

1 Determine the cable’s VOP using Table 3-1and enter it into the TDR.

2 Connect the two leads to both conduc-tors at one end of a duplex pair. (Asnoted earlier, a TDR cannot trace a sin-gle conductor.)

3 Turn off the power to the circuit beingtraced. If you don’t, the Fault MapperTDR will give you an on-screen promptthat voltage is present.

4 Push the “test” button on the unit, andthe unit will trace the circuit.

The photo sequence shows the testingcapabilities, as well as some limitations, of theTDR.

What’s the issue regarding lightbulbs? Thefilament in the bulb completes the circuit byconnecting the positive and negative feed con-ductors. The same thing happens if you twistthe bare ends of two conductors together. TheTDR’s signal bounces from one of the pairedconductors to the other, and in both cases thebouncing stops where the circuit is completed,


The TDR has identified an open circuit 21.6 feet (6.6 m) away. If youknow how the wiring harness in question is routed through the boat, youcan work your way right to the problem to make the necessary repair.Does it seem too good to be true? It might be, if you don’t have a clearunderstanding of what else might be implied by this reading.

junction BDC –

DC +

battery

switch open cabin light

cabin light

junction A

TDR will pick up junction A or B as either a short or open in the circuit

The TDR can “map” only as far as the first junction——a short circuit——in a cir-cuit (the first limitation). To continue tracing a circuit beyond a junction, youmust find the junction (the TDR has told you how far away it is) and isolatethe next leg of the circuit by disconnecting the branch in question. Forexample, if a cabin light circuit contains a tee to feed a light on the oppo-site side of the boat, as shown here, you will have to disconnect that feedwire from the main harness and trace each branch of the circuit separately.

The TDR indicates a short circuit 30.6 feet (9.3 m) away,but this is a red herring. Another limitation with a TDR isthat lightbulbs show up as short circuits. In this case, thereis, indeed, a (perfectly functional) navigation light 30.6 feetaway from the TDR.

2

3

4

at the farthest point from the source of the sig-nal. The unit can only tell you where thebouncing stops; it can’t determine if it’s an opencircuit, a short circuit, or a complete circuit.Thus, you really need to know how a circuit islaid out and what components are installed onit to correctly interpret the TDR’s results.

Using the TDR to Check Wire Size

In addition to finding faults in a circuit, you canuse a TDR to determine if a circuit complieswith ABYC standards for wire size. Here are thefacts we know about the circuit example above:


The 3% voltage drop table from ABYC Standard E-11. (Courtesy ABYC)

• The navigation light being tested in photo 4opposite is working.

• The 12 V circuit is wired with 14 AWG wire.• The total length of the circuit from the

panel to the light and back to the source is61.2 feet (30.6 feet � 2).

• The lightbulb draws 2 amps.

Navigation lights are a critical circuit, andthe ABYC (and U.S. Coast Guard) permits amaximum 3% voltage drop. We then refer tothe appropriate voltage drop table in ABYCStandard E-11, reproduced below.

For safety’s sake, the ABYC recommendsalways “rounding up” when using voltage droptables. In this case, that means we have toround up from 2 amps (actual) to 5 amps, thelowest value on the table. We also have toround up the length, from 61.2 feet (actual) to70 feet (the next higher value on the table).This table shows that we should use 8 AWGwire for both the DC positive feed to the lightand the DC negative return.

If this seems excessive, we can use theABYC’s circular mil area formula (from Stan-dard E-11) as an acceptable alternative to thetable. Let’s work the numbers. Our factors forthe problem are:

CM (circular mil area)�(K � I � L) � E,where:

K (constant for the resistivity of copper) � 10.75

I (load current in amperes) � 2

L (total circuit length in feet) � 61.2

E (acceptable voltage drop of 3% for 12 V) �0.36

Therefore:

CM � (10.75 � 2 � 61.2) � 0.36 � 3,655

Next, compare the calculated CM value tothe circular mil table from ABYC E-11 shownopposite. You’ll see that even when roundingup to the next nearest size from 3,655 CM, wehit the 14 AWG row at 3,702 CM. That’sgood news; the circuit wiring is compliant.

There is often a huge difference betweenthe CM calculation method and using thetables in E-11, as the above example illustrates.In fact, I rarely use the tables, and almostalways perform the calculations using actual


values, with no rounding. It often results in asmaller wire size requirement that still meetsstandards. For a boatowner, this can save sev-eral dollars on a single circuit. For professionaltechnicians, it can save tons of copper per year!

Does the TDR play a major role in this?You bet. Because you can check the actuallength of the wire runs, you can confirm com-pliance in factory-installed, aftermarket, andrepaired wiring. No one should be able to pulla fast one on you by fudging wire sizing.

VALUE AND UTILITY

The tools described in this chapter are versatileand can be used for any type of wiring or cir-cuit, AC or DC. (Just be sure the power is offwhen using them, since these tools can’t func-tion with power running through the wiring.)The tone-generating circuit tracer is a highlyaffordable tool. And while a bit more expen-sive, the AEMC Fault Mapper is also a tonegenerator, so instead of purchasing both tools,you can add the AEMC model TR02 receiverto the TDR and have the benefits of bothmethodologies described in this chapter com-bined into one kit.

In the case of the TDR, you may need todo a little additional homework to gather moreVOP values, but if you’re a marine electrician,you have the wire lying around on rolls. Allyou’ll need are minimum 60-foot lengths tostart building your own library of VOP values.Once you’ve done that, yet another value of theFault Mapper will stand out—the ability tocheck inventory by checking how much cableis left on the roll! I’ll never use an ohmmeterfor this type of work again.


The conductor circular mil area and stranding table from ABYC Standard E-11. (Courtesy ABYC)

C H A P T E R

4Testing AC andGrounding Systems forPolarity, Voltage Drop,Impedance, and Frequency

In the “old days,” the tools of choice for working around AC systems on boats were theDVOM and maybe an oscilloscope. Today, the advanced technician or boatowner caneasily test conductor impedance, polarity, frequency level, voltage drop, and peak RMS

voltage with a circuit analyzer.

THE SURETEST CIRCUIT ANALYZER

As far as I can determine, the SureTest circuit analyzer from Ideal Industries is a uniqueinstrument that, although now in its second generation, still represents the only exampleof this new category of test devices. Our discussion will use model 61-164. (A sister modelis available that adds a testing capability for arc fault circuit interrupters, but since AFCIsare not used on boats, this feature is not of interest to us.)

As with many of the tools outlined in this book, the SureTest 61-164 circuit analyzeruses a microprocessor, which allows it to perform six extremely important tests on an ACsystem in a matter of seconds. It comes with probes for testing receptacles and has anoptional alligator clip. At around $250, I consider this tool to be worth every penny andan absolute necessity for anyone working around AC systems.

Now, let’s go through each test function one by one.

SureTest model 61-164, Ideal Industries, Inc., www.idealindustries.com

CIRCUIT ANALYZER


4 7

Checking for Polarity

One of the most common errors in AC wiringis improper connection of the hot, neutral, orground wire at receptacles, which can be anelusive problem. According to ABYC Stan-dard E-11, most 120 V wired boats arerequired to have a reverse-polarity indicator atthe main AC panelboard. However, the panelindicator only monitors from the shore-powerpedestal to the panel; receptacles suppliedfrom the panel are not monitored by the indi-cator. If they have been mistakenly miswired,the panel indicator won’t pick it up, creating apotentially dangerous situation at that recepta-cle. By using the SureTest at every receptacle

testing ac and grounding systems

on the boat, you can easily check the polarityand determine if you have to take action.

In this application, the SureTest replicatesthe functions of a $5 circuit tester that youprobably already own. Don’t worry; this instru-ment is capable of much more sophisticatedand useful testing, but these basic tests areimportant, so we’ll review them first.

Here are the basics for testing polarity:

1 Plug the SureTest into an active receptacle.

2 The tester’s screen display should immedi-ately light up.

3 The unit will progress from its openingscreen to a display of three green LEDsindicating hot, ground, and neutral.

4 If all three LEDs are lit, it’s a firm indica-tion that polarity is correct—in otherwords, hot and neutral have not beenreversed.

5 Other LED combinations indicate variousAC wiring problems—an open-circuited(not connected) hot or neutral, no-ground situations, and false grounds.

The SureTest 61-164 circuit analyzer. Wiring Condition

Correct Wiring

No Ground

Polarity Reversal

Open/Hot Neutral

False Ground

Display Indication H G N

Legend On Off Flashing

F

The SureTest indicates different AC wiring problems by displaying vari-ous combinations of its three LEDs.

One of the limitations of the tester is thatit will not detect reversal of the neutral andgrounding conductors, which is a possibility ifthe receptacle installer was really careless.However, the grounding terminal on recepta-cles is always indicated by a green lug, so youcan visually see the error. The grounding ter-minal is not obvious with the hot and neutral,and the SureTest will pick it up in a flash as areversed polarity condition.

“False” GroundsSince false grounds can create dangerous situ-ations on a boat and/or in the water around it,they warrant further discussion. A false ground,for our purposes, is a ground connection toneutral at a location other than the source ofpower. In other words, it is a point where anAC neutral conductor is “falsely” connected tothe AC grounding, or earth, conductor.


Proper neutral-to-ground bonding of an isolation transformer, according to Standard E-11. (Courtesy ABYC).

The U.S. National Electric Code (NEC)only allows a neutral-to-ground link at thedistribution panel for AC systems. The ABYC,on the other hand, only allows neutral-to-ground links at sources of AC power on boardthe boat—primarily generators, inverterswhen they are producing AC, and the second-ary side of isolation transformer sets, as shownin the illustrations. If the boat is not equippedwith any of these devices, the neutral andground must be separated all the way back tothe shore-power distribution panel. At thatpoint, the NEC code takes precedence.

Neutral-to-ground bonds are important atAC power sources because if there is a shortcircuit at an AC appliance, it means that the“hot” has shorted to the equipment case, effec-tively bypassing the neutral conductor. Bytying the neutral and ground conductortogether at the source of power, the fault cur-rent is provided with an alternative path back

to the source and a circuit breaker will trip,shutting off the circuit. Remember that thegreen ground wire is attached to the case ofAC equipment, which is key to the success ofthis configuration.

So here’s the rub, but in the case of boatsit’s actually a useful one. The SureTest willidentify these “false” grounds within about 15to 20 feet of the occurrence of a neutral-to-ground link, including a distribution panel,onboard generator, inverter, or isolationtransformer. So in a nutshell, “false” may beexactly what you are looking for at thesedevices. It’s at AC appliances that you don’twant this link. A good example of where afalse ground may appear is at a 240 V electric

4 9testing ac and grounding systems

range or clothes dryer that is wired for olderresidential applications, which are often installedon older boats (see photo page 50).

These neutral-to-ground links must be dis-connected when installed on a boat (see photopage 51). Otherwise, every time you turn onthe appliance, you run the risk of AC power(which would normally be returned down theneutral conductor) being pushed down thegrounding conductor, and possibly enteringthe water via the DC bonding system. Remem-ber that on ABYC-compliant boats, the ACand DC grounding systems should be linkedeither at the engine’s negative terminal or, occa-sionally, at the grounding buses behind theboat’s main AC and DC distribution panels.

Proper neutral-to-ground bonding of an inverter, according to Standard E-11. (Courtesy ABYC).

So the SureTest’s indication of a “false”ground may be either a good or a bad thing,depending upon whether it has identified aproper link at an AC power source or animproper one at an AC appliance or a recep-tacle. You’ll need to confirm or deny which isthe case by performing a little visual inspec-tion detective work of all the devices men-tioned, and physically tracking down theneutral-to-ground link.

Voltage Measurements

The second test in the sequence is the linevoltage measurement. Categorically, line volt-age should be maintained at a maximum of±10% of the rated voltage. For 120 V poten-tial, voltage should be between 108 and 132VAC; for 220 systems, the range is 198 to 242VAC.


Proper neutral-to-ground bonding of a 120 VAC generator, according to Standard E-11. (Courtesy ABYC).

neutral-to-groundlink to case

A neutral-to-ground link on the back of a 120/240 V electric range——afalse ground. Another common appliance where this may occur is elec-tric clothes dryers.

Since the SureTest 61-164 will also mea-sure peak voltage, you can get a feel for dis-tortion by calculating the theoretical peak atline voltage � 1.414, and comparing it to theactual measured peak. You won’t be able tosee the distortion as you can with the oscillo-scope, but you’ll be able to determine if itexists, and calculate it if it is excessive (seeChapter 7).

Besides basic line voltage and peak val-ues, the unit will also test for neutral-to-ground leakage. (Press the “advance” arrowkey to go to the next test in the sequence.)This value should always be less than 2 VAC.More than 2 VAC is an indication of exces-sive current leakage from neutral to ground.This condition is typically caused by thebreakdown of insulation within an appliance,or possibly by two terminals that are barely


Always look for labeling on the back of an appliance forgrounding instructions, and be absolutely certain that theneutral-to-ground link is disconnected on a boat installation.

touching, creating a partial, though high-resistance, connection. In a 220 V multiple-phase system, high neutral-to-ground leakagecould indicate severely unbalanced legsbetween the phases or excessive harmonic dis-tortion on the shared neutral. These conditionscan create equipment performance problems,as described in Chapter 7.

Table 4-1 on page 52 summarizes voltagereadings, expected results, problems, and pos-sible causes and solutions.

Voltage Drop Measurements

As already stated, excessive voltage drop is oneof the marine electrical system’s biggest ene-mies. I’ve also noted that the primary by-product of excessive electrical resistance isheat, and that too much voltage drop is thesame as excessive resistance. This is an areawhere the SureTest really shines. As far as Iknow, it’s the only test instrument that can applya load to the wiring at three levels (12 amps,15 amps, and 20 amps) and calculate the voltagedrop as a percentage within a few seconds.

With this information in hand, trou-bleshooting is easy. Based on NEC recom-mendations, anything in excess of 5% is toomuch. If excessive voltage drop exists, it maymean that the wire gauge is too small for thetask at hand, or there is a poor-quality con-nection somewhere in the circuit. To confirmor reject this, simply retest at points closer tothe source and see if the problem goes away asyou get closer to the source. If it does, thenthe problem is between the high-readingcheckpoint and the low-reading checkpoint,with several possible causes:

• a loose connection in that leg of thecircuit

• undersized cabling, perhaps added to theoriginal circuit

• a faulty receptacle that needs replacing


Expected Possible Possible Measurement Result Problem Causes Solutions

Line voltage 108—132 VAC High/low Too much load on Redistribute loads on the120 VAC the circuit. circuit.

Line voltage 220 AC 198—242 VAC High-resistance Locate high-resistanceconnection within connection/device andthe circuit or at repair/replace.the panel.

Supply voltage too Consult power company.high/low.

Neutral-ground < 2 VAC Voltage High G—N > Current leaking from Identify source of leakage: voltage 2 VAC neutral to ground. multiple bonding points,

equipment, or devices.

Unbalanced three- Check load balance andphase system. redistribute load.

Triplen harmonics Oversize neutral toreturning on neutral impedance. Reduce harmonicin three-phase effect via filter or othersystem. methods.

Peak voltage 153—185 VAC High/low Supply voltage too Consult power company.120 VAC peak voltage high/low.

Peak voltage 280—242 VAC High peak loads on Evaluate number of electronic220 VAC line caused by devices on circuit and

electronic equipment redistribute if necessary.on line.

Frequency 60 Hz High/low Supply frequency too Consult power company.frequency high/low.

Source: Ideal Industries, Inc.

Voltage Troubleshooting TipsTABLE

4-1

Physically check these possibilities and repairor replace cables or components as needed.

This is also an area where the infrared heatgun (see Chapter 5) can be useful in findingthe hot spot in the circuitry. Use Table 4-2 tohelp you troubleshoot voltage drop problems.

Impedance Measurements

To further assist you in troubleshooting exces-sive voltage drop, the SureTest can measurethe exact impedance (resistance) in each of thethree conductors in a circuit. Again, I know ofno other tool that has this capability.

If measured voltage drop is more than 5%,a problem exists. Using the meter’s arrow keys,scroll through the menu to read and comparethe impedance values for the hot, neutral, andground conductors. What you are looking forhere is parity among the conductors.

If impedance in one conductor is signifi-cantly higher than another, then you’ve narroweddown the problem. Again, loose or corrodedconnections are the most probable cause, andyou must now physically search out the culprit.

If all the conductors read high, then thecabling is probably undersized. Keep in mind

that if the circuit is protected by a GFCI(ground fault circuit interrupter) or a GFP(ground fault protection) device, the devicewill trip during this test. Simply reset it afteryou’ve acquired the values.

Use Table 4-3 to help you troubleshootimpedance problems.



Voltage drop < 5% High voltage Too much load on the Redistribute the load on the drop circuit. circuit.

Undersized wire for length Check code requirements of run. and rewire if necessary.High-resistance connection Locate high-resistancewithin the circuit or at connection/device andthe panel. repair/replace.


Voltage Drop Troubleshooting TipsTABLE

4-2


Hot and neutral < 0.048 �/foot High conductor Too much load on Redistribute the load on theimpedance of 14 AWG wire impedance branch circuit. circuit.

< 0.03 �/foot of Undersized wire for Check code requirements 12 AWG wire length of run. and rewire if necessary.

< 0.01 �/foot of High-resistance Locate high-resistance 10 AWG wire connection within the connection/device and

circuit or at the panel. repair/replace.

Ground < 1 � to protect High ground Undersized wire for Check code requirements impedance people impedance length of run. and rewire if necessary.

< 0.25 � to High-resistance Locate high-resistanceprotect equipment connection within the connection/device and

circuit or at the panel. repair/replace.


Impedance Troubleshooting TipsTABLE

4-3

Measuring Available Short-CircuitCurrent

The SureTest can also measure (in kiloamps, kA)the amount of available short-circuit current(ASCC)—how much current can flow througha circuit in spite of resistance factors such as wiregauge and terminal connections. This will be

significant when you consider circuit breakerratings, because if the ASCC is greater than theampere interrupting capacity (AIC) rating for abreaker or fuse, the device may not functionwhen a short circuit occurs. Instead, in the caseof the breaker, the contacts can be weldedclosed, and in the case of a fuse, the fuse elementcan arc.

ABYC Standard E-11 establishes AIC limitsfor AC and DC breakers and fuses, as shown inthe ABYC table below. Simply put, whateverreadings the SureTest gives you on this testsequence, you need to be sure they are belowthe AIC ratings shown in the table. Typical AICratings for circuit breakers used in AC applica-tions will exceed this value, in my experience.For example, on docks I’ve checked, the ASCCreadings were well below the AIC ratings on thebreakers used due to the voltage drop inducedby the wire gauge and length of wire runs typi-cal of marina and dock wiring schemes. Com-mon ASCC readings on docks I’ve checked fallin the 1,000 to 2,000 amp range.

GFCI and GFP Testing

One more useful SureTest function is testingGFCI and GFP devices. (GFPs are also


known as RCDs—residual current devices,and EPDs—equipment protecting devices.)The ABYC describes GFCI devices as thoseintended to protect people from shock haz-ards associated with AC faults, and GFPdevices as those intended to protect equip-ment from damage. The big difference in thisapplication between a SureTest and a $5 LEDcircuit tester is that a SureTest will measureboth the trip rate (in milliamps, mA) and thetrip time for the GFCI or GFP. This informa-tion can warn you of the device’s imminentfailure. Considering the statistically high fail-ure rate of GFCIs, particularly in marineapplications (more on GFP testing in aminute), the ability to perform these tests isof paramount importance.

During the test, the instrument creates asmall but steadily increasing current imbal-ance between the hot and neutral conductors.The GFCI should respond by trippingbetween 4 mA and 7 mA. Most GFCIs thatI’ve checked trip at 7 mA if all is well. Notethat the nominal rating of GFCIs in NorthAmerica is 5 mA, but as with all breaker-typedevices, the nominal rating and the actual triprate are always different values.

NOTES: 1. The main circuit breaker shall be considered to be the first circuit breaker connected to a source of AC power.All subsequent breakers, including sub-main breakers connected in series with a main circuit breaker, shall be consid-ered to be branch circuit breakers.2. A fuse in series with, and ahead of, a circuit breaker may be required by the circuit breaker manufacturer to achievethe interrupting capacity in TABLE V-B.

The circuit breaker interrupting capacity for systems over 50 V from ABYC Standard E-11. (Courtesy ABYC)

Here’s how to perform the GFCI test:

1 Plug the tester into the GFCI or GFCI-serviced receptacle.

2 Press the “GFCI” button on the tester.

3 If the GFCI is working, it will trip, andthe instrument will display the trip rate inmA just before it blinks out.

4 To display the trip time, simply reset theGFCI. How much time is too much? Thenominal trip delay time for GFCI devicesis 0.025 second or 25 milliseconds (ms).

5 If your readings are not close to thesevalues, replace the GFCI receptacle.

To test GFPs, simply depress the side arrowkey on the face of the tester to the 30 mA set-ting and perform the test as described above.

This is an extremely valuable capabilitybecause it corresponds to the 30 mA trip ratethat is a requirement for whole-boat protec-tion everywhere in the world except NorthAmerica. Such whole-boat protection consistsof a 30 mA rated GFP installed at the boat’smain shore-power connection. Any currentleakage on the boat that gets to the 30 mAlevel will turn off the power to the entire boat.(I am lobbying at the standards development


level for the United States to adopt thisrequirement.) Typically, boats coming to theUnited States from Europe, New Zealand, andAustralia are equipped with these devices, andany U.S. boats shipped to those regions mustinstall them. Boats from Asia, on the otherhand, are often built specifically for the U.S.market and are therefore wired to NorthAmerican standards.

Use Table 4-4 to help you troubleshootGFCI problems.

The following photos show the completetest sequence of this very useful device.


GFCI test GFCI trips within GFCI doesn’t GFCI may be installed Check wiring for proper trip time. trip within improperly. installation in accordance

proper trip with manufacturer’s time. instructions and NEC.GFCI doesn’t GFCI may be defective. Check wiring and ground.trip. Replace GFCI if necessary.


GFCI Troubleshooting TipsTABLE

4-4

Circuit testing, similar to what you can do with a simple $5LED tester. In this case, the SureTest indicates “no ground,”a dangerous condition.

1


Testing line voltage. The SureTest shows 119 V at the out-let. Any reading within ±10% of nominal voltage (120 V)is acceptable.

Testing neutral-to-ground leakage (voltage). The SureTestshows 0.9 V, which is acceptable.

Testing peak voltage value. The SureTest shows 168.5 V,which is normal.

Measuring voltage drop with a 15 amp load. TheSureTest shows 15.5%, which is too high; it should be 5%or less. High readings like this can indicate poor-qualityterminations in the system or undersized wiring.

Testing frequency in Hz. The SureTest shows 60 Hz, which isthe expected result; ±5% is the maximum accepted tolerance.

Checking voltage drop with a 20 amp load. The SureTestshows 20.7%, which again is too high.

2 3

4 5

6 7


Testing ASCC. The SureTest shows 0.08 kA (80 amps).This result won’t cause problems for the circuit breaker, butit does indicate that undersized wiring may have beenused to construct the circuit. (The smaller the wire, the lesscurrent it can carry.)

Other Options

The SureTest comes equipped with enoughprobes for testing receptacles, while theoptional 61-183 alligator clip adapter is a use-ful option for checking power supplies thatare hard-wired to AC equipment. You willalso need to make an adapter (see the sidebaron page 58) for the shore-power connection,

like the one shown above, and possibly sev-eral adapters if you plan to test various ser-vices (30 amps, 50 amps, etc.).

For 50 amp, 240 V service, I usually checkL1 and L2 as two separate entities using two50 amp plug sets that key into the L1 hot andL2 hot terminals. Keep in mind that in NorthAmerica, a 240 V system is similar to two

Measuring the actual (as opposed to the rated) trip ratefor a GFCI device. The 7.3 mA value is perfectly normalfor a 5 mA rated device.

Measuring the trip rate for a GFP. The SureTest shows30.6 mA, which is close to the 30 mA trip rate requiredfor whole-boat protection (outside the United States).

plug SureTestinto 15 A

plug 30 A intoshore-power pedestal

A homemade 30 to 15 amp adapter for checking dockwiring.

8 9

10


MAKING SURETEST ADAPTERS

It’s relatively easy to make adapters to use the SureTest to check 240 V, 50 amp shore-power service.You will need to buy two 50 amp replacement plug assemblies (male plugs) and two 15 amp femaleplug assemblies to plug the SureTest into. You’ll also need about 2 feet of four-wire 240 V, 50 ampshore cord or the equivalent.

You need to make two assemblies so you can test the ground, neutral, and 120 V “hot” lead foreach leg of the 240 V system. Construct one assembly (B) so that the hot lead connects to the L2 ter-minal (see the illustration) and the grounds (green or GR) and the W (white) terminals connect to the240 V plug. Construct the other adapter (A) the same way, except connect the hot lead from the15 amp plug’s small-bladed terminal to the 240 amp plug’s L1 terminal.

Use about 1 foot of the shore-power cabling for each adapter. Mark the L1 and L2 connectionswith an indelible marker for future reference. The illustration shows how the completed adaptersshould look.

A

B

black, L1

50 amp, 240 V plugassemblies

standard 15 amp plugassemblies

white

gray, not connected

gray, L1,not connected

white = neutralblack, L2, connected

green

gray

black

green

black = "hot"

gray = neutral

The L1 and L2 conductors and the neutrals and grounds. In A, L1 in the 50 amp plug is activated from the15 amp assembly. Both white terminals are activated, and both green terminals are activated as grounds. In B, theblack terminal in the 50 amp plug is the L-shaped prong, which becomes L2, and is connected to the blackterminal on the 15 amp plug. The white and green terminals are continuous.

120 V systems combined, so each L, either 1or 2, is actually a separate 120 V service.Remember the tool only comes equipped witha three-prong 15 amp plug set, so you willhave to make some plug modifications formarine applications.

VALUE AND UTILITY

The SureTest is the tool I use most with ACcircuit analysis, and I think anyone workingwith AC systems should own one. When you

use it, keep in mind that the electrical toler-ance specifications discussed above apply tomost of North America, and that other areas(that provide 120 V, 60 Hz service or 240 V,four-wire service) may have different require-ments, which you should confirm locally.


C H A P T E R

5Temperature Monitoringas a Diagnostic Aid

The primary by-product of excessive electrical resistance is heat, which can be anelectrical system’s worst enemy. Along with causing early failures of expensive elec-trical and electronic equipment, excessive heat can cause fires. A recent study con-

ducted by BoatU.S. determined that 55% of all boat fires are caused by faulty electricalinstallations. It’s no wonder the ABYC addresses excessive electrical resistance and heatbuildup in several standards dealing with electrical installations and equipment.

Since heat is such an important issue, a few years ago I decided that I should measureit in electrical systems, just as I had always done with engine cooling systems and refriger-ation systems. Enter the heat sensor or heat-sensing gun, which is basically a handheldinfrared thermometer. The unit uses an invisible infrared beam to sense the energy that isemitted, transmitted, or reflected from an object and translates that data into temperature. Italso has a laser beam for aiming and an internal battery. They range in price from $30 to $150.

Because the laser and infrared beams can go where you cannot go, or perhaps may notwant to go (remember we’re dealing with excessive heat), it is a handy device for locating anumber of potential problems:

• loose cable termination points• damaged or corroded terminals• undersized wiring• faulty relays and switches (these will run hotter than normal if they have bad internal

connections)

Model 42500, Extech Instruments, www.extech.com (replaces model 42520)Model TG-600, Greenlee, www.greenlee.com60 series, Fluke, www.fluke.comModel T-7350, Professional Equipment, www.professionalequipment.comModel 22-325, RadioShack, www.radioshack.com

INFRARED HEAT SENSORS


6 1

INFRARED HEAT-SENSINGGUN

So what should you look for when choosing aheat-sensing gun? Two specifications areimportant: temperature range, and distance-to-spot ratio.

Temperature Range

The most important specification is the heatgun’s temperature range. Some inexpensive

temperature monitoring

units have a range from slightly below 0°F to500°F or so (–18°C to 260°C), which is finefor electrical troubleshooting and work on air-conditioning and refrigeration systems. How-ever, if you intend to use the gun for otherareas of troubleshooting as well, such as look-ing for temperature variations between cylin-ders on engines or tracing coolant flowthrough the engine’s cooling system, you maywant to spend a little more and get a unit thatcan read up to 1,000°F (538°C) or evenhigher. (Typical operating temperatures ofcylinders and exhaust systems can exceed1,000°F.) It’s also useful if the unit displaysresults both in degrees Fahrenheit and Celsius(outside the United States, Celsius is thetemperature-measuring unit of choice, andequipment manufacturers may list perfor-mance specifications in either units).

The RadioShack model listed in the sidebarwill work fine for electrical troubleshooting, butits measurement scale (0°F to 400°F/–18°Cto 204°C) may not be sufficient for the entirerange of applications discussed here. Forengine work, exhaust systems, and other high-temperature applications, look for a unit with arange of approximately 5°F to 1,000°F (–15°Cto 538°C).

Distance-to-Spot Ratio

The second specification to consider is thedevice’s distance-to-spot ratio, which is the ratioof the distance to the object (D) to the diameterof the infrared beam (S), or D:S. Simply put, asthe infrared beam moves farther away from thegun, the diameter of the beam widens. Conse-quently, as the effective width of the infraredbeam increases, the device measures tempera-tures across a larger area. For example, with a12:1 ratio, if you aim at a spot 24 inches away,the diameter of the beam at the spot will beroughly 2 inches; with a 6:1 ratio, if the meteris 12 inches from the target, the diameter willbe 2 inches. The illustration shows two ratios,

The Extech #42520 infrared heat-sensing gun. (Note: Thismodel was recently replaced by model #42500.)

6:1 and 12:1, with various distances. (Note:The ratio is calculated in millimeters, so thestandard inch measurements only approxi-mate the ratio.)

Generally you will want to measure thetemperature of a small target, such as an elec-trical termination, so a larger distance-to-spotratio is better, providing you with the flexibilityto take accurate measurements from a greaterdistance.

In practice, I have found a 6:1 ratio to besatisfactory for boat work. (The Extech unitshown in this chapter has a 6:1 ratio, whichlimits its useful distance to a maximum ofabout 4 feet/1.2 m; otherwise the sample areagets too large.) I’ve found this distance to bequite satisfactory for anything I’ve ever neededaround boats. As I’m typically checking thetemperatures at wire and cable terminationpoints or along the length of a conductor,I don’t need a long range, nor do I want tocover a very large area in my measured sample.


S

29 mm @150 mm

38 mm @300 mm

57 mm @600 mm

1.1“@ 6”

1.5“@ 12”

2.3“@ 24”

D

S

25 mm @150 mm

50 mm @300 mm

100 mm @600 mm

1“@ 6”

2“@ 12”

4“@ 24”

D

infraredheat sensor gun

infraredheat sensor gun

D__S

6__1

–– D__S

–– 12__1

D = distance S = spot size D = distance S = spot size

area of coverage area of coverage

Infrared distance-to-spot ratios for both a 6:1 and 12:1 configuration.

Using an Infrared Heat Gun

Learning to operate an infrared heat-sensinggun is relatively easy. However, knowing howto use it and interpret the results is a bit morecomplicated. Here are some important pointsto keep in mind:

• As noted earlier, electrical resistance pro-duces heat. An electrical problem oftenresults in increased resistance, and thusincreased heat. So we are looking forabnormal heat readings, not necessarilyhigh temperatures, because as we allknow, some electrical devices normallyrun hot during operation.

• A change in temperature (for example,from one point in the circuit to another)is more important than the temperaturereading on the heat gun. In other words,we are looking for a temperature differen-tial. (The actual average temperature willvary depending upon ambient temperature

changes in the area you are working in.The trick is to look for abnormalities.)

• If there is no current flow, there will be notemperature change. The circuit in ques-tion needs to at least be trying to work forthe heat gun to acquire any relevant tem-perature readings.

It’s best to use the gun after everything hasbeen shut down for a bit, and the ambienttemperature has stabilized throughout what-ever system you are checking. The reason isthat after a system has been in use for a time,thermal transfer from one part to another hasoccurred (i.e., the temperature has risen in thespace), and the pronounced temperature dif-ferential you are looking for will be muchharder to find. Copper wire is not only a goodconductor of electricity, it’s also a great con-ductor of heat. (In fact, it can act as sort of aheat sink for whatever it’s attached to.) If acomponent and its wire are at the ambienttemperature, and the connection is loose, thenalmost immediately after you turn on thedevice, you’ll see a marked increase over ambi-ent temperature at the connection.

I have found that the best way to use a heatgun is to first scan the area where you will beworking to determine the average ambienttemperature. This is your benchmark. Then,when you scan a specific termination or deviceand find a much higher temperature (e.g.,25°F higher), you will know you’ve discovereda potential problem.

Let’s look at a common real-world appli-cation: I have tested my boat’s charging systemand gotten some lower than normal readings,which could be caused by a loose connectionanywhere in the alternator/battery circuit. Istart checking for a bad connection at thepositive battery terminal on the back of analternator. I run the test with the 225 hpYamaha outboard engine running, and thealternator is working pretty hard charging up

6 3temperature monitoring

laser beam

Here the heat gun is testing the quality of the main battery connection atthe starter motor on my engine. The thermometer shows a reading of90°F (32°C), which is close to the outside temperature. If the tempera-ture at the connection rises significantly when cranking the engine, afaulty connection is indicated. In this case, all was well and no change intemperature was indicated while cranking.

some house bank batteries that have been dis-charged.

I point my heat gun at the front of the alter-nator and get a average reading of 186°F(85.6°C). As I move my laser beam around abit, I point it directly at the stator windingthrough a ventilation opening near the middleof the alternator case. I get a reading of 211°F(99.4°C)! As I move the laser beam to the backof the alternator and point it directly at the pos-itive battery terminal, I get a reading of 196°F(91°C). As I track my laser beam down the con-ductor, away from the alternator, the tempera-ture gradually drops to 163°F (72.8°C).

What have I learned? Nothing, other thanthe fact that the alternator gets pretty darnhot! The wire is conducting some of the heatgenerated by the alternator at the terminal,eventually reaching the average temperature inthe small engine area of the boat.

No problem was indicated by this test, butlet’s run it again, starting with a stone-coldengine. As soon as I turn on the engine, I addsome electrical loads—all the onboard DClighting, the blower fan, and navigationequipment—to get the alternator workinghard. Now I quickly take some measurements,before the engine, components, and the com-partment have a chance to heat up.

This time, I see a rapid increase of 25°F atthe terminal compared to the surroundingarea. Because this large temperature differen-tial is so isolated, it’s a pretty good indicationthat the terminal should be removed andinspected for damage or corrosion. Rememberthat the amount of heat produced variesdirectly with the amperage in the circuit andthe resistance in the conductor or terminationpoint (more amps = more heat potential).

Note that only high-current DC circuits—those connected to things like bow thrusters,starter motors, alternators, and anchorwindlasses—have the capability to generateenough heat for the infrared heat gun to be auseful diagnostic tool. On the AC side ofthings, the gun is useful for tracing from ashore-power pedestal through to the boat andat receptacles that have loads plugged in andoperating. The heat will invariably show up ator near the terminal ends, assuming that thewire gauge sizes were appropriate to begin with.

OTHER USES FORTEMPERATUREMONITORING

Up to now, we have used temperature moni-toring as a means for identifying electricalproblems. Now let’s shift our focus a bit tomonitoring temperatures to avoid problems.Admittedly, this falls outside the normalscope of troubleshooting, so let’s call thisexercise “trouble prediction and avoidance”instead.


temperaturesensor

The infrared temperature sensor on the MidtronicsinTELLECT EXP-1000 diagnostic meter.

Batteries, Battery Chargers, andInverters

Some components on boats need to be kept ascool as possible to ensure proper or even con-tinued operation. Examples include isolationtransformers, DC-to-AC inverters, and bat-tery chargers, all of which generate fairly hightemperatures.

In the case of battery chargers and inverters,the issue is important enough for the ABYC toaddress it in a standard. ABYC Standard A-31(adopted July 2005) for manufacturers of bat-tery chargers and inverters states, “Batterychargers and inverters shall be designed to oper-ate at 122°F (50°C) continuously and be ableto withstand a maximum of 158°F (70°C).”

Regarding batteries, we saw in Chapter 2how temperature monitoring was one func-tion of the Midtronics inTELLECT EXP-1000. In some marginal situations, the tem-perature of a battery can affect the test results,in which case the diagnostic meter will directyou to measure the battery temperature usingits built-in infrared sensor (measurement

range from –20°F to 200°F) so it can compen-sate for the temperature.

In this same vein, many battery chargershave potentiometers that allow for temperaturecompensation adjustments based on the aver-age temperature of the battery compartment.

6 5temperature monitoring

The temperature display on the inTELLECT EXP-1000.

These adjustments, which maximize batterycharging voltage output potentials, are oftenoverlooked, but they can make a real differencein battery performance and longevity. Theinfrared heat-sensing gun can help here as well.

Galvanic Isolators

Temperature can also be a critical issue withdiode-type galvanic isolators in several ways.First, a high case temperature may indicate aserious AC fault on the boat and a safety issue.There could be enough AC fault current flow-ing through the isolator to heat the case butnot high enough current to trip a breaker, cre-ating a shock hazard.

Second, galvanic isolators have beenknown to fail due to excessive ambient tem-peratures in their mounting locations. It is notat all uncommon for low-level currents to berunning through an isolator for indefiniteperiods of time, resulting in a buildup of heat.This heat must be dissipated; otherwise, thediodes that are the key components within theisolator can be damaged from the thermaloverload. ABYC Standard A-28 for manufac-turers of galvanic isolators defines the ambienttemperature for isolators that are eitherignition-protected or intended for installationin machinery spaces at 122°F (50°C). Fornon-ignition-protected isolators and thosethat are not intended for installation in machinespaces, ABYC pegs the ambient temperatureat 86°F (30°C).

VALUE AND UTILITY

Before installing a galvanic isolator, batterycharger, or other similar device on your boat,it makes sense to check temperatures to deter-mine the suitability of a specific locationand/or the need for supplemental ventilation.(In fact, this should be part of a professional-grade installation.) A normal thermometer

Temperature compensation adjustment on a batterycharger.

will do the job, but an infrared heat gun willgenerate results much faster.

Temperatures matter in electrical work,and excessive temperatures are a bad thing.Careful monitoring of equipment, circuits,and spaces will help you identify problems

before they become serious or even dangerous.With an infrared heat sensor, you also canaccurately determine when equipment needsservicing or replacing and have solid informa-tion for installation decisions.


C H A P T E R

6Using Power Factorto Determine EnergyEfficiency

Sooner or later, marine electricians and boatowners are confronted with the termpower factor. For work on small boats, power factor is usually not too much of a con-cern, but as boats get bigger and bigger, with more AC-powered gear than ever

installed, it warrants careful consideration and perhaps even monitoring.Warning: At 110 V or 240 V, AC power on boats—whether shore power or pro-

vided by AC generators and DC-to-AC inverters—is potentially lethal. If you are notcompletely confident in your abilities around AC circuits, call in a specialist.

UNDERSTANDING POWER FACTOR

What is power factor? One definition states it as: “The ratio of real power to apparentpower delivered in an AC electrical system or load. Its value is always in the range of 0.0 to1.0 or 0% to 100%. A unity power factor (1.0) indicates that the current is in phase withthe voltage and that reactive power is zero.”

Hmmm. Everybody still with me? Let’s break that definition down a bit:

• Factor describes a proportional relationship between two quantities—in this case, realpower and apparent power.

• Real power (also known as active power or working power) describes the amount ofelectrical energy that is converted into useful work.

• Apparent power describes the total electrical energy actually delivered by the powersupply (i.e., a utility company, an AC generator, or a DC-to-AC inverter).

• Reactive power is the difference between the power delivered and the power convertedto useful work.

It may be helpful to think of power factor as the amount of current and voltage thecustomer actually uses compared to what the utility supplies. A high power factor is con-sidered to be 90% or more.


Reactive Power

While reactive power may seem to be loss ofpower, it isn’t a complete loss. In fact, reactivepower is necessary to generate the magneticfield that is essential for the operation ofmotors, transformers, and similar devices with awound coil. When a refrigerator compressormotor is turned on, there’s a brief time lagbetween the moment the thermostat trips andthe moment the motor begins to turn. It is dur-ing this ever-so-brief interval that reactivepower is working. This is part of the reason whymotors on start-up typically draw anywherefrom three to six times their running current.

Reactive power needs to be controlled sothat the devices function, but the public elec-tric utility (or the boat’s generator or inverter)doesn’t recognize the inherent disparity, whichin effect requires delivery of more power overa period of time. The amount of reactivepower required needs to be minimized. All ofthis equates to more than simple inefficiency.Ultimately it affects the entire power-deliverysystem—things like transformer sizing, wiregauge appropriate to handle the increasedcurrent demands, and the like.

When you apply this concept to equip-ment and appliances, you move into the area ofpower consumption. How do your appliancesand equipment rate? Low-power-factor itemscan have a significant impact on your boat’selectrical system. For example, a low-power-factor fluorescent light ballast will draw morecurrent than a high-power-factor ballast for thesame wattage lamp. The result is that fewer ACappliances can operate on a given circuit.

On a boat with many AC circuits poweringpumps and motors for refrigeration systems, airconditioners, and such, it’s possible to have afairly low cumulative power factor (i.e., thepower factor for the total amount of watt-hoursconsumed). In extreme cases, this may requireadditional shore-power service to the boat.

IMPROVING YOUR POWERFACTOR

Power factor is most commonly improved byincorporating capacitor banks in a device. Thecapacitors charge and discharge on demand tosupply the reactive power needed by the load.By engineering the capacitor bank correctly,an electrical designer can achieve, or at leastget very close to, the desired 1.0 unity factormentioned above. Once power factor correc-tion circuitry is installed, the need to draw thereactive power from the AC supply source iseliminated or greatly minimized.

You can test the equipment and applianceson your boat to determine their power factor(see below). You may be able to upgrade toappliances and equipment that have a bettercorrected average power factor. All appliancesthat are “Energy Star” qualified have highpower factors, which can significantly improveyour power efficiency. For example, in thehome construction field, a home that is certi-fied as Energy Star qualified can be as much as15% to 30% more electrically efficient, interms of watt-hours used per month.

DETERMINING POWERCONSUMPTION

Performing an AC system load analysis is animportant part of ensuring that there isenough available capacity to operate a boat’sequipment based on typical use and con-sumption habits. (Note that the same appliesto DC service, but we will be dealing withAC service only.) In many cases, boaters areattempting to add air conditioning or refrig-eration systems to older boats. Such systemstypically use quite a bit of power and oftenrequire installing additional, isolated shore-power service to the boat, which can beexpensive. (Using an Energy Star appliancemight make the difference between having to


6 9using power factor

AC LOAD ANALYSIS (FROM ABYC STANDARD E-11)

11.10.2. FOR AC SYSTEMS

11.10.2.1. Power Source Options

The method shown in E-11.10.2.2 shall beused for calculating the total electrical loadrequirements for determining the size of panel-boards and their feeder conductors alongwith generator, inverter, and shore-powercapacities. The total power required shall besupplied by one of the following means.

11.10.2.1.1. Single Shore-Power Cable. Ashore-power cable, power inlet, wiring, andcomponents with a minimum capacity to sup-ply the total load as calculated, complyingwith E-11.7.2.1.1.

11.10.2.1.2. Multiple Shore-Power Cables.Multiple shore-power cables, power inlets,wiring, and components shall have a minimumtotal capacity to supply the total load as cal-culated complying with E-11.7.2.1.1. Allsources need not be of equal capacity, buteach power inlet shall be clearly marked toindicate voltage, ampacity, phase (if a three-phase system is incorporated), and the loador selector switch that it serves.

11.10.2.1.3. Onboard AC Generator(s) orInverter(s). Onboard AC generator(s) orinverter(s) to supply the total load as calculated.Total minimum installed kVA [kilovolt amperes]for a single-phase system is as follows:

kVA � Maximum Total Leg Amps � SystemVoltage � 1000

11.10.2.1.4. Combination of Shore-PowerCable(s), Onboard Generator(s), andInverter(s). A combination of power sources,used simultaneously if the boat circuitry is

arranged such that the load connected toeach source is isolated from the other in accor-dance with E-11.5.3.6. Shore-power cable(s)plus onboard generator(s) and inverter(s)capacity shall be at least as large as the totalelectrical load requirements as calculated.Generator(s) and inverters(s) installation andswitching shall be as required in E-11.7.3.

11.10.2.2. Load Calculations

11.10.2.2.1. The following is the methodfor load calculation to determine the mini-mum size of panelboards and their mainfeeder conductors as well as the size of thepower source(s) supplying these devices.(See E-11.10.2.1.)

11.10.2.2.1.1. Lighting Fixtures and Recep-tacles.

Length times width of living space (excludesspaces exclusively for machinery and opendeck areas) times 20 watts per square meter(2 watts per square foot).

Formula:

Length (meters) � width (meters) � 20 �_________ lighting watts, or

Length (feet) � width (feet) � 2 �_________ lighting watts

11.10.2.2.2. Small Appliances, Galley andDinette Areas.

Number of circuits times 1,500 watts for each20-ampere appliance circuit.

Formula:

Number of circuits � 1,500 � _________small appliance watts

(continued)


11.10.2.2.3. Total.

Formula:

Lighting watts � small appliance watts �_________ total watts

11.10.2.2.4. Load Factor.

Formula:First 2,000 total watts at 100% � _________

Remaining total watts � 35% � _________

Total watts � system voltage � _________amperes

11.10.2.2.5. If a shore-power system is tooperate on 240 volts, split and balance loadsinto Leg A and Leg B. If a shore-power systemis to operate on 120 volts, use Leg A only.

Leg A / Leg B ______ / ______ Total Amperes

11.10.2.2.6. Add nameplate amperes formotor and heater loads:

Leg A / Leg B ______ / _____ exhaust and supply fans______ / _____ air conditioners *, **______ / _____ electric, gas, or oil heaters*______ / _____ 25% of largest motor in

above items______ / _____ Subtotal

NOTES: *Omit the smaller of these two, except includeany motor common to both functions.

**If the system consists of three or more independentunits, adjust the total by multiplying by 75% diversityfactor.

11.10.2.2.7. Add nameplate amperes atindicated use factor percentage for fixedloads:

Leg A / Leg B ______ / ______ Disposal——10%______ / ______ Water heater——100%______ / ______ Wall-mounted oven——75%

______ / ______ [Stovetop] cookingunit——75%

______ / ______ Refrigerator——100% ______ / ______ Freezer——100% ______ / ______ Ice maker——50% ______ / ______ Dishwasher——25% ______ / ______ Washing machine——25%______ / ______ Dryer——25% ______ / ______ Trash compactor——10% ______ / ______ Air compressor——10%______ / ______ Battery charger——100% ______ / ______ Vacuum system——10% ______ / ______ [Sum of] other fixed

appliances______ / ______ Subtotal ______ / ______ **Adjusted subtotal

NOTE: **If four or more appliances are installed on aleg, adjust the subtotal of that leg by multiplying by 60%diversity factor.

11.10.2.2.8. Determine Total Loads. Leg A / Leg B

______ / ______ Lighting, receptacles, and small appliances (fromE-11.10.2.2.5)

______ / ______ Motors and heater loads(from E-11.10.2.2.6)

______ / ______ Fixed appliances (fromE-11.10.2.2.7)

______ / ______ Freestanding range(see Note 1)

______ / ______ Calculated total amperes(load)

NOTES: 1. Add amperes for freestanding range as dis-tinguished from separate oven and cooking units. Deriveby dividing watts from Table III [opposite] by the supplyvoltage; e.g., 120 volts or 240 volts.

2. If the total for Legs A and B are unequal, use thelarger value to determine the total power required.

Nameplate Rating (watts) Use (watts)

10,000 or less 80% of rating10,001—12,500 8,00012,501—13,500 8,40013,501—14,500 8,80014,501—15,500 9,20015,501—16,500 9,60016,501—17,500 10,000

Ratings are for freestanding ranges as distinguished from sep-arate oven and cooking units.

Freestanding Range RatingsTABLE

III

add additional service capacity or not.)ABYC Standard E-11 offers a fairly completesection on performing an AC load analysis,and it really mirrors the techniques pre-scribed by the NEC. The sidebar on pages69–71 excerpts this material from ABYC E-11.

USING A POWER ANALYZER

I use a WattsUp? portable power analyzer madeby Electronic Education Devices. Although thename may sound a little silly, the WattsUp? isactually a high-tech, microprocessor-drivendevice with great utility. Because wattage or,more precisely, watt-hours are what utility com-panies base their billing on, the WattsUp? deviceis quite useful in performing power consump-tion analysis on many boats. With it, you can:

• Perform power consumption analysis bymeasuring wattage used.

• Calculate the cost of operation for a pieceof equipment. Program in the local utilitycost per kilowatt-hour and allow the unitto run through a normal daily servicecycle (typically, 24 hours).

• Measure line voltage to an appliance.• Measure amperage draw, minimum

amperage draw, and maximum amperagedraw. These values are useful for deter-mining appropriate wire sizes and over-current protection device ratings.

• Calculate power factor, which is primarilywhat I use it for.

The WattsUp? portable power analyzer. Six main modes display the pri-mary data: watts, kilowatt-hours, time, cost, volts, and current.



Selling for around $150, the WattsUp? isaffordable, and costs far less than high-end,scope-type power analyzers, such as the Flukemodel 434, which run between $4,000 and$4,500. (Unless your work involves largemarina or shipyard power systems and mega-yacht-sized vessels, this cost would be hard tojustify, since power analysis is not somethingthat needs to be done all that frequently.)Unfortunately, the WattsUp? works only with120 V, 60 Hz appliances, so its usefulness isessentially limited to North America.

The unit is simple to operate, requiringonly that you plug it in between the appliancein question and any 15 amp receptacle and letit run.

If the appliance is hard-wired into theboat’s AC system (which is the case with manybattery chargers, for example), simply makeup a 15 amp, three-prong plug assembly withan insulated three-terminal strip to temporar-ily disconnect from the boat and connect tothe appliance feed cable. Using this adapter,

WattsUp?, Electronic Education Devices, www.doubleed.com (available through ProfessionalEquipment, www.professionalequipment.com)

PORTABLE POWER ANALYZER

plug the WattsUp? into a conventional wallsocket and attach the three-wire adapter to theappliance via ring terminals at its power inputbus and the three-prong plug at the other endof this short jumper (about 12 to 18 inchesworks fine) plugged into the WattsUp?.

Warning: Turn off all power to the appli-ance you are connecting this adapter to untilall the terminations are made. Shock hazardexists if you inadvertently grab one of thelive wires that you’ve temporarily exposed.

Comparing Power Consumption

I recently used the WattsUp? to compare two6,000 Btu air conditioners; the newer one wasan Energy Star qualified unit, and the otherunit was about five years older. I’ve summa-rized my results in Table 6-1.

These differences may not seem like much,but on a boat equipped with multiple unitscycling all the time, the cumulative differenceover time can be considerable.

Average Draw Peak Draw Power Factor (compressor (at compressor Power Factor (compressor

running; watts) start-up; watts) (fan only) running)

Older unit 800 1,901 1.0 0.89Newer, Energy 560 1,724 1.0 0.98

Star unit

Power Consumption of Two 6,000 Btu Air ConditionersTABLE

6-1


In researching industrial motors like theones used in marine air-conditioning and refrig-eration systems, I discovered power factor speci-fications ranging anywhere from 0.57 to 0.95—quite a spread in what ultimately amounts to theefficient use of power. But beyond efficiency,power factor also relates to such important issuesas the amperage-carrying capability of supplyconductors, the susceptibility of equipment toundesirable voltage drop, and the potential forheat buildup and insulation damage due toexcessive electrical resistance.

Think of it this way: appliances with lowpower factor values will use more power(wattage), and typically require more amper-age to function. This means that larger feedconductors will be needed to supply theappropriate amperage. Additionally, sincemore current must be delivered, undersizedwiring will contribute to potentially excessivevoltage drop. Any AC appliance that is run-ning continually at lower than specified volt-age will run hotter than it should, and thatexcessive heat can ultimately be the cause forbreakdown of insulation on motor windings

and the like. The bottom line here is that thelongevity of the appliance will be affected andyou are going to be wasting power.

A good resource for motor specifications isavailable through the U.S. Department ofEnergy at http://www1.eere.energy.gov/industry/bestpractices/software.html. Once you get tothe site, you will find a free software downloadfor MotorMaster+ 4.0, which enables you tocompare a large number of motors by per-formance specification and to calculate andcompare their cost of use over time.

VALUE AND UTILITY

The WattsUp? is not the first tool theadvanced marine electrician or boatownershould purchase, but it does have utility forload analysis of AC systems. It won’t work onhigh-current-draw items like electric rangesand ovens, but for refrigeration systems,microwave ovens, and other commonly usedconvenience appliances, it can tell you a lotabout power consumption characteristics.

The power factor rating for the more efficient unit, which is pluggeddirectly into the front of the WattsUp? instrument.

C H A P T E R

7Analyzing HarmonicDistortion

AC waveform analysis on an oscilloscope may sound like a pretty sophisticatedprocedure. And indeed it is, but not for the user, because the sophisticationoccurs within the instrument itself. It’s therefore a practical troubleshooting pro-

cedure for any marine electrician or a boatowner committed to running an electricallyefficient boat.

When you think of oscilloscopes (commonly called scopes), you may picture the bread-box-size instruments of long ago. But as with all things electronic, the scopes used todayhave come a long way. Vacuum tubes are ancient history, and transistors and computerchips have taken over, enabling vendors to make some small, yet excellent, handheld devicesthat really perform. These units are not in the low-priced gear category, although I’ve seensome advertised for as little as $300. The unit that’s shown in this chapter is from the Fluke860 series, and costs about $2,000. (Note: This has recently been replaced by the 190 series.)

DO YOU NEED A SCOPE?

On a modern boat, AC can be supplied by a variety of sources, and sometimes even a com-bination of sources. Shore power is only one part of the picture. AC generators, DC-to-AC inverters, and converters that modify incoming voltage and frequency are becomingmainstream—even on boats that historically were considered too small to bother withdockside power.

Unless you do a lot of work on complex AC systems with inverters, generators, andtransformers that perform voltage and frequency conversions, an oscilloscope shouldnot be the first tool on your wish list. You can get almost as much utility from a high-end multimeter with a “peak hold” feature and data-logging capability. For those whowould like to get into the oscilloscope game without investing several thousand dollars,I recommend the Extech 381 series scopes, which cost approximately $250 to $400.

190 series, Fluke, www.fluke.com (replaces the 860 series)381 series, Extech Instruments, www.extech.com

OSCILLOSCOPES


7 5

Unfortunately, some of the electronic equip-ment routinely installed on boats can deliver lessthan satisfactory performance when powered bydistorted AC sine waves. For example:

• flat-screen televisions—may displaydiagonal lines

• some audio systems—may generateannoying background noise

• regular TV screens—may develop anaudible “hum” and display diagonal lines

• some computer systems, especially sys-tems using a UPS (uninterruptible powersupply)—may work but run too hot; maytry to turn on and off; or may not work atall (note that all the laptops I’ve triedwork fine with an inverter; some desktopsmay be affected)

analyzing harmonic distortion

printer or PC connection

line or battery power

hard keyssoft keys

rotary selector

test leads

The Fluke 867B graphical multimeter is a full-feature multimeter and oscillo-scope. It also has the ability to log data over time, and upload it to a PCfor further analysis, something we’ll address in Chapter 8.

A classic symptom of a faulty waveform isa piece of gear that functions perfectly whenrun from the shore-power supply, but acts upwhen run from an inverter or generator.

The good news is that with an oscilloscopeyou can see and analyze the AC waveform todetect harmonic distortion (see below).

AC LOADS

Let’s look again at the part of the power factordefinition in Chapter 6 that stated “a unitypower factor (1.0) indicates that the current isin phase with the voltage.” To understandthis, we need to look at some additional defi-nitions and take a closer look at what happensin an AC circuit depending upon AC loadcharacteristics.


ALTERNATING CURRENT AND WAVEFORMS

A perfectly formed AC sine wave, characteristic of ACpower as delivered by a utility company.

AC current forms sine waves when voltageis charted against time. The waveform dis-played on the oscilloscope is a true sinewave. Although the nominal voltage is120 volts at 60 cycles per second, thescope shows the voltage as slightly lessthan that, at just over 117 VAC. This is com-pletely normal; voltage variations of �10%are not uncommon.

Some of the equipment we use on boatsdoesn’t always deliver a perfect sine wave,however. Generators sometimes developmechanical or electrical problems that canaffect their ability to maintain precise enginerpm, and frequency and voltage, as well asthe waveform, can become skewed. Theoscilloscope will display this faulty waveform,as well as frequency and voltage values thatfall out of acceptable parameters (generally�10% for voltage and �5% maximum forfrequency). Many inverters don’t even attemptto deliver a perfect AC sine wave, but rather willdeliver AC current in a stepped-square-wave,or modified-square-wave, output. CharlesIndustries, one major vendor of inverters,offers at least one unit that bills itself as aquasi-sine-wave inverter. This appears to bemore marketing hype than anything else. Thebottom photo shows the waveform as deliv-ered by one of these inverters. These invertersshow these “stepped” waveforms becausethe unit is taking DC current, which shows as aflat straight line on an oscilloscope, and con-verting it to what I’ll call a usable form of ACcurrent. The “steps” are created by the elec-tronic switching that is occurring in the inverter,which is really nothing more than the powerturning on and off as it gets “stepped up” toAC voltage potentials. More sophisticatedinverters will have more electronic switches,which in effect creates less profound “steps”

A modified square wave, or “quasi-sine” wave, asCharles Industries calls it, the company that distributesthe DC-to-AC inverter this reading was taken from. Thesequasi-sine waves represent a certain level of distortion. Ifyou have an inverter, you have to figure out whether theappliances you’re attempting to power with the invertercan operate in spite of the inverter’s distortion.

differential across the bulb’s filament, the fila-ment has an engineered amount of resistance,and the resistance generates enough heat tomake it glow brightly. The relationship betweenthe voltage delivered and the resistance of thefilament determines the current draw throughthe circuit.

Nonlinear loads, which work on the princi-ple of inductance, include devices such astransformers, motors, solenoids, and relays.These have a more complex relationship be-tween volts and amps.

First, a magnetic field develops around anywire or conductor through which current is flow-ing. The strength of the magnetic field is propor-tional to the amount of current (i.e., amperage).

Second, we also know that we can induceelectrical current flow through a conductor bymoving a magnet rapidly in close proximity tothe conductor. A transformer is simply a pair ofwire coils in close proximity to one another, withan iron core in the middle to contain the mag-netism. As we pass alternating current throughone of the transformer’s coils (the primary wind-ing), an alternating magnetic field is created. Thefield rapidly rotates around the secondary wind-ing, and electrical current flow is induced (at 60times per second, or 60 Hz, in North America,and 50 Hz in most of the rest of the world).Sounds perfect, right? Well, it isn’t quite.

In fact there is a loss through the trans-former, resulting in some inefficiency. Thelevel of this inefficiency is a function of har-monic voltage levels at a transformer’s primarywinding versus load-generated harmonic cur-rent (nonlinear) levels at the output terminalson the secondary side of the transformer, anda phase relationship is established. To explainmore simply, remember that both voltage andamperage in AC circuitry are not constant asin DC circuitry. Alternating current (and volt-age) is delivered as waves—there are peaks andvalleys. When we measure 120 VAC with amultimeter, the actual peak voltage is usually

7 7analyzing harmonic distortion

and will smooth out the curve, or wave. It isimportant for boatowners and technicians tobe aware of this because some equipmentrequires true-sine-wave output to function prop-erly, as discussed on page 75.

Sine wave

Square wave

Modified sine wave

120V

170V

150V

Pulse width varied tomaintain 120 volts RMS

A comparison of inverter waveforms. (Reprintedwith permission from Boatowner’s Illustrated Elec-trical Handbook, second edition, by CharlieWing)

Load Types

AC loads can be divided into two categories:linear and nonlinear. Linear loads basicallydraw current in proportion to the voltagedelivered, much like a DC load where Ohm’slaw applies. That is:

amperage � volts � ohms

A basic incandescent lightbulb is a goodexample of a linear load. There is a voltage


on the order of 165 to 170 VAC. But it doesvary slightly due to forces within the devicesthat are powering up, which either slow thingsdown a bit or speed them up. When this hap-pens, the waveforms become slightly dis-torted, and we end up with slightly skewedwaveforms. The term used to describe thiseffect is harmonic distortion.

HARMONIC DISTORTION

Harmonic distortion is defined in theNational Electrical Code as “a load where thewave shape of the steady-state current does notfollow the wave shape of the applied voltage.”As we just discussed, the bottom line is thatnonlinear loads—such as audio equipment,computers, fluorescent lighting with ballast,and variable-speed motors—will put AC-sup-plied voltage out of phase with amperage. Thenet result is a waveform that becomes slightlydistorted when viewed with an oscilloscope.Linear loads—such as a water heater or anincandescent lightbulb—will not create thisphase imbalance between voltage and current.But all of this is quite esoteric, and really dragsus into advanced electrical engineering con-cepts that go beyond what I am trying to con-vey here. What’s important for the boatowneror technician to understand is that excessiveharmonic distortion can create problems withsome common onboard AC equipment.

The illustrations show a change in the rela-tionship of voltage and current in an inductiveload scenario (top illustration), which couldbe a transformer or a motor, and in a capaci-tive scenario (bottom illustration), whichcould be a noise filtration circuit on some-thing like an audio amplifier. In the inductivescenario, the voltage is leading the current. Inthe capacitive scenario, the current leads thevoltage. These are typical scenarios for thesebroad load categories, but don’t get too caughtup in all of this. Again, what the boatowner ortechnician needs to know is that things are

inductive load

voltage leads current by

90˚ in phase

90˚V

I

AC power source

Voltage (V) is leading the current (shown as amperage, I)because it takes time for the voltage to force the buildupof current to its maximum across an inductive load.

voltage lags current by

90˚ in phase90˚

V

capacitor

AC power source

I

Another example is what happens in a capacitor as itcharges and discharges. In this case the voltage lagsbehind the current because the current must flow to buildup the charge in the capacitor. The effect is known ascapacitance, which is the ratio of the electric charge trans-ferred from one to the other of a pair of conductors to theresulting potential difference between them.


ending up a bit out of phase and waveformdistortion will occur as a result. (Rememberthat resistive loads do not have these faults andare generally thought of as linear; there is noinductance or capacitance to worry about.)

Regardless of whether an AC circuit is sup-plying an inductive load, a capacitive load, ora resistive load, there are factors that will mod-ify the perfect AC current sine waveform.

Excessive harmonic distortion may causeequipment to overheat, motor failure, capacitorfailure (especially in motor circuits), and exces-sively high, neutral conductor current. Com-monly used devices that may either contributeto or be affected by excessive distortion include:

• fluorescent lights• some HVAC systems• computers, printers, and fax machines• dimmer switches for lighting• audio equipment• video equipment• UPS devices

Here’s an example of how harmonic distor-tion is created. In order to work, a fluorescentlight first requires a buildup of voltage. Oncethe voltage is high enough, an arc occursacross its pair of electrodes. At this point, cur-rent flows easily, especially when compared tothe current flow before the arc occurred. Ineffect, the light draws nearly no current ini-tially and much more current once the tube isactivated and producing light.

Multiply this effect by a power grid’s cumu-lative nonlinear loads, and the net effect is a dis-torted sine wave delivered to the boat. Extremedistortion can be seen on an oscilloscope visuallyas a sine wave that has uneven peaks and valleys,often with a “flattened” top to one of the wavepeaks (see top photo page 81).

Harmonic distortion can be cumulativewithin a power grid, and will be distributedthroughout the grid, potentially causingequipment problems. Determining whether

excessive distortion exists is one of the moreadvanced troubleshooting exercises a boat-owner or technician may find themselves per-forming at some point.

Finding Harmonic Distortion

Finding the source of harmonic distortion isnot always easy. Harmonics can migratethrough the power distribution system fromone building or marina to another, and fromone boat to another in a marina, if they areconnected electrically via the utility powergrid. Furthermore, the problem can be inter-mittent, as electrical loads that cause distor-tions may cycle on and off. Monitoring must,therefore, be done over an extended period oftime. In fact, some power analysis specialistsrecommend site monitoring over a period ofone month to gather quantifiable data! Thismakes a strong case for the data-loggingmethodologies we’ll look at in Chapter 8.

If you have equipment that is exhibitingharmonic distortion symptoms—the mostcommon ones are overheated or damaged ACneutral conductors or cable terminations, andcircuit breakers that trip continually and mys-teriously—you can use your oscilloscope toconfirm your suspicions.

Connecting an oscilloscope to an AC cir-cuit is easy. Plug the meter’s red lead into themeter’s AC volts socket and the black lead intothe “com” socket, as in the photo on page 75.Then connect the other ends of the leads as ifyou were measuring voltage: red lead to thehot terminal, and black lead to the neutral ter-minal. Next you’ll select the appropriate func-tion for the meter you are using.

Calculating Distortion Using PeakCapture

Although special power-analyzing meters arecurrently available, they are cost prohibitive,especially when you consider that evenadvanced marine electricians will not be usingthis equipment that frequently. But with an

oscilloscope, or with a high-end DVOM thatalso has a “peak capture” feature, you can get apretty good indication of whether excessivedistortion exists in an AC power supply. This“peak” is the maximum point we see when look-ing at the sine wave on an oscilloscope; i.e., thehighest voltage measured in the AC waveform.

Crest factor describes the ratio of the peakvalue of a measured waveform to its root meansquare (RMS). A pure, undistorted sine wave’screst factor, therefore, is described by theequation:

1 � 0.707 � 1.414

In other words, the peak voltage value of anundistorted sine wave is 1.414 � the true RMSvalue. Any variation from this value indicates adistorted waveform and bad harmonics. Usinga peak-capture-capable DVOM, here’s how toperform these measurements, step by step:

1 First, measure the true RMS value of thevoltage at a receptacle. When using a trueRMS meter, the reading will be automaticif you are set to the VAC scale on the meter.

2 Multiply that reading by 1.414 to estab-lish the theoretical peak value.

3 Check the actual peak value with the peakcapture feature on your meter.

4 Compare the actual value with the theoret-ical value. If they differ by more than 2%or 3%, excessive harmonic distortion exists.

To differentiate between voltage and cur-rent harmonics, consider these points:

• For voltage harmonics, the typical crestvalue will be less than the product of theRMS value � 1.414. On an oscilloscope,this will appear as a “flat top” on a sine-wavecurve, as shown in the top photo opposite.

• For current harmonics, the typical crestvalue will be greater than the productof the RMS value � 1.414. On an

oscilloscope, this will appear as an abnor-mally high peak.

As an example, let’s use the numbers dis-played in the bottom left photo opposite tocalculate distortion. To keep things simple,we’ll round the RMS value down to 121.

We begin by determining the theoreticalpeak by multiplying the RMS value by 1.414:

121 � 1.414 � 171 VAC

Our actual measured peak (see Peak Maxon scope), at 161 V, is lower than that value,which would appear as a flat-top waveform onan oscilloscope.

Subtract the measured peak from the theo-retical peak:

171 � 161 � 10 V

Divide the difference by the theoretical peak:

10 � 173 � 6%

Since 2% to 3% is considered the allow-able limit, this system has excessive distortion.

Current Multiplication

Excessive current in neutral conductors is acommon phenomenon in the three-phasepower supplies (where three sinusoidal volt-ages are generated out of phase with oneanother) typical of many marinas. Before weleave this discussion of harmonic distortion,we need to understand how and why it occurs.

In a well-balanced, three-phase AC circuit(which is how all AC power begins in shore-power installations), there are always har-monics as the wave of the current alternates.Even-numbered harmonic currents canceleach other out; odd-numbered harmonics donot—in fact, they add algebraically, causingthe neutral conductors in a three-phase system(the white wire in North America) to carry asmuch as 180% of the amperage carried byeach of the three individual phase conductors.This particular problem has been identified in



A peak value result on an oscilloscope. A typical true RMS voltage reading for a 120 V system.

A typical distorted flat-top waveform.


office buildings for some time, and mayaccount for the seemingly strange symptom ofa burned-up neutral conductor with all otherconductors in the system looking fine.

The most common transformer type used incommercial and industrial environments isknown as a Delta-to-Wye transformer, in whichthe transformer’s primary windings are in a Deltaconfiguration, and the secondary windings are ina Wye (see illustration). We can see that the neu-tral has to serve each of the three hot-wire legs toget the current back to its source; i.e., the trans-former. Since this neutral conductor is typicallythe same gauge as the hot wires, it’s easy to seehow it might be overburdened at times.

Transformer overheating is not only anothereffect of harmonic distortion exposure, it pre-sents another potential problem on boats thatuse transformers for shore-power isolationand/or as voltage step-up or step-down devices.The infrared heat gun discussed in Chapter 5 isa great tool for determining whether a problemexists. Temperature readings greater than 120°Fto 125°F (49°C to 51.7°C) indicate either atransformer that is underrated for the task athand or is exposed to excessive harmonics.

Harmonic distortion was of little con-cern to boatowners and technicians when

the AC load on boats was typically only awater heater, perhaps an electric stove, andmaybe a TV. But as we’ve discussed, theequipment on boats has gotten more sophis-ticated, and consequently more sensitive todistortion in its power supply. So it is nowimportant for the advanced technician orboatowner to have an understanding of har-monics to ensure the safety and reliability ofAC systems.

VALUE AND UTILITY

If you regularly work on larger boats or boatswith AC generators, inverters, or any combi-nation thereof, I recommend that you con-sider investing in an oscilloscope. If time ismoney, and most say it certainly is, then you’llfind that a small scope will answer some keyquestions about power supplied to the boatvery quickly and easily. As boats get more andmore sophisticated, and we find ourselvesworking on 35-footers equipped with multi-ple AC power sources, flat-screen TVs thatrise up out of a saloon table, and high-endaudio systems, etc., the value of using a scopewill become evident in no time at all whenproblems occur.

208 V

208 V

208 V

120 V

120 V

120 V

A

"WYE"

B

C

A

C

B

Delta configuration—primary side of transformer Wye configuration—secondary side of transformer

neutral

A Delta-to-Wye transformer showing the differences in configuration between the primary and secondary windings of the unit.

C H A P T E R

8Using a Laptop forIntermittent Problems

One of the first troubleshooting steps is confirming or denying the existence of aproblem, and one of the most difficult troubleshooting challenges is the intermit-tent problem. You know—the problem that doesn’t show up when you want it to.

The troubleshooting process also requires that you understand the conditions underwhich the problem occurs. Unfortunately, at today’s labor rates it is totally impractical toachieve these goals in many cases. Who wants to pay a technician hundreds of dollars justto sit around waiting for a problem to occur? And few boatowners have the time to con-duct extensive in-use testing with the sole objective of waiting for an intermittent problemto recur.

One way to deal with this situation is to let your equipment do the sitting around foryou, gathering data that you can analyze later. Sometimes environmental conditions trig-ger intermittent electrical problems and often these conditions can be duplicated as partof a sea trial. Simply attach data-logging equipment to the circuit(s) in question and putthe boat through a sea trial, running the boat’s systems through their normal operationalcycles while the data-logging equipment does its work. Keep a log during the sea trial, not-ing sea conditions, wind velocity, engine rpm, boat speed, precipitation, and even temper-atures in the area of the meter at given times throughout the test. This will enable you tolater match the environmental conditions to the data-log time stamp on your laptop as anaid to analysis of the data. After the sea trial, check the measurements and key them toevents during the sea trial.

LAPTOP LINK-UPS

Like so much of the equipment discussed in this book, the microchip is the driving forcebehind the data-logging capabilities of just about any piece of high-end electrical measur-ing equipment you are likely to buy today. The software involved is not complex, so itdoesn’t need the latest and greatest in a PC or laptop. I use an otherwise outmoded PC asmy platform for data logging.

Typically, a PC that is at least Windows 95 compatible will suffice. You won’t needmuch storage either, as all the logging programs I’m familiar with are essentially text basedand don’t require a huge hard drive or lots of memory.


Multimeters and other instruments withthe capability to record measurements tointernal memory or upload them to a com-puter are available from equipment supplierssuch as Fluke, AEMC, and Extech. You willneed the appropriate software from the metervendor. This may be included in the price ofthe meter or available as a low-cost option(typically in the range of $30 to $60). Addi-tionally, you will need a data-link cable to con-nect the meter to your PC, which is generallyincluded with the software and in most cases isa serial port connection. By following normalPC software installation procedures, andselecting a communications port for your PC,you should be ready to go in no time.

Most meters can be programmed to recorddifferent intervals of data “hits.” For example,


my Fluke 860 with FlukeView software allowsme to program data sampling in 1- to 45-secondintervals or 1- to 15-minute intervals. Depend-ing upon what you are checking—rapidchange or change over extended periods oftime—this is an important adjustment. Also,if you are monitoring over a 24-hour period,you may want to extend the sample-ratetime period to conserve hard drive space onyour PC.

No adjustments are required in how youconnect the meter to the circuit—volts, amps,and ohms are tested the same way as withnon-data-logging instruments. The onlyessential difference is the use of spring-loadedalligator clips instead of straight test probesto hold the leads in place while the meter goesto work.

A somewhat outmoded laptop or PC capable of running Windows 95 or better is generally sufficient to capture outputfrom most equipment into data-logging software.

Additional Advantages

While our primary focus is identifying inter-mittent problems, having a PC or laptop link-up has other advantages. For example, thelarger screen of a computer versus a metermagnifies your view dramatically. This is par-ticularly useful when looking for distortion inAC waveforms. Even if your multimeter oscil-loscope has the technical capability to capturesubtle problems, the size of the display (2 to4 inches, typically) may make it difficult toobserve. But if you blow up the view on a 14-or 15-inch PC or laptop screen, those prob-lems become obvious. For example, the flat-tening at the peak of the wave shown in thetop photo on page 81 is easy to see when mag-nified on a computer screen but would be hardto see on a 2- to 4-inch multimeter display.

If you are a professional technician, sendingdata logs to a computer opens up several possi-bilities. You can save and print customer files,include screen shots in a customer’s report, orimprove your internal documentation andquality control processes. It’s easy to do, and itadds a level of professionalism to your workthat is unprecedented in the marine field.

REAL-WORLD EXAMPLES

Let’s look at some real-world cases where youmight consider data logging as a useful aid introubleshooting.

Example 1: Unexplained UnderwaterMetal Corrosion

One of the classic problems affecting boats inmarinas is rapid, unexplainable corrosion ofunderwater metal components. Often, whengoing through a complete corrosion analysis,you may find no measurable problem. Theproblem could be cycling of appliances orequipment, such as an air conditioner or bilgepump, either on your own boat or one nearbyat the dock. So what do you do?

You want to capture stray current in thewater surrounding the affected boat “afterhours.” Link a tracking multimeter, fitted witha special silver/silver chloride reference elec-trode (see Chapter 11), to your computer, andimmerse the electrode in the water near theaffected boat. The computer link-up willrecord the data, allowing you to either confirmor rule out the presence of stray current. Ifthere is stray current, you’ll be able to pinpointthe exact time and date of the measurement.More important, you will have confirmed aprobable cause of corrosion, without having tomake five repeat trips to the boat to try and“catch” the problem. And, if you’re a techni-cian, you avoid having to report to the clientthat “no problem was found at the time of sur-vey.” Or if you’re a do-it-yourselfer, you won’thave to hang out on the boat all night, lookingat the multimeter readout every 10 minutes.

Example 2: Instrument Lighting ThatFails Only When Underway

In this example, the backlighting on your dash-mounted engine monitoring instrumentsblinks on and off when motoring in rough seaconditions. Most people would immediatelyattribute this problem to a loose electrical con-nection feeding the lights. But a look at theelectrical feeds to the dash lights has come upwith nothing, and the size and complexity ofthe boat’s overall wiring make it difficult toinspect every connection for every wire. Fur-ther complicating the diagnosis is the fact thatthe instruments are backlit by LEDs mountedon a printed circuit board. The problem might,therefore, be in the power supply or groundreturn for the PC board, or it might be on theboard itself, which is sealed and integrated withthe backside of the instrument housing.

To troubleshoot this problem, you shouldlog data while reproducing the conditions inwhich the problem occurs. Attach a data-loggingmultimeter to the power supply and ground it to

8 5using a laptop

the instrument cluster. Then take the boat for asea trial in rough seas until the dash lights beginto blink. You can then confirm whether or notthe power feed to the printed circuit board isaffected. If not, and the problem occurs, it’s a safebet the problem is in the PC board itself, whichin all probability needs to be replaced.

By using this methodology you haveturned a two-person job (one to operate theboat, the other to watch the meter face) into aone-person/one-instrument job and created a

situation where you can run the test withoutany special scheduling or logistical arrange-ments. Plus you have isolated the location ofthe problem without employing frustratingtrial-and-error tactics.

These methods are truly a more efficientapproach to problem solving. Boatownersdoing their own work will find answers morereadily, and for the marine professional, thisefficiency will pay off in less wasted time andbetter customer service.


odd

odd

A sample of a DC log. Notice the time and date stamps with each entry. All you need to do is scan these data entriesand pick out the odd entries, such as those marked, then try to associate the time they occurred with events that mighthave caused them. For example, if a problem occurs on the unoccupied boat between 5 P.M. and 8 P.M., it could beassociated with the use of electric galley stoves on other boats at the dock. If it occurs at fairly regular intervals, but onlyduring hot weather, it might be an air-conditioning unit.

C H A P T E R

9Testing forElectromagnetic andRadio FrequencyInterference

As boats become more complex, and we continue to install more and more electri-cal and electronic gear on board, the potential for electromagnetic and radiofrequency interference (EMI and RFI) increases. When you combine this with the

space restrictions on boats, you’ll see the challenges installers face in finding suitablelocations for all the equipment carried by the average boat today.

UNDERSTANDING ELECTROMAGNETIC INTERFERENCE

The ABYC electrical standards state that wire and cable runs need to be thought out whenthey are being installed in close proximity to “magnetically sensitive devices,” such as the boat’scompass. But the truth is that we need to consider far more than just the compass and mag-netic sensitivity. For example, all microprocessors use clock oscillators that create a digitalsquare waveform (see Chapter 7). This waveform is not only loaded with distortion and har-monics, it is affected by stray emissions as well. Devices such as fluxgate electronic sensors(used as direction sensors on autopilots), satellite TVs, and satellite telephones are alsoextremely sensitive to excessive interference. Tales abound of electronically controlled enginesdisplaying strange running conditions—such as running rough or excessive black exhaustsmoke—when certain, seemingly unrelated, electrical devices were activated. Certainly overthe years there have been cases where electronic navigation systems have been brought to theirknees due to RFI (Loran-C was particularly vulnerable), and I’ve even heard stories of lightsmysteriously turning on and off when someone keyed a single-sideband radio to transmit.

These strange symptoms are more easily understood in the light of two basic concepts:

1 All wire and cable that have electricity moving through them will have a magneticfield surrounding them.

2 The strength of this magnetic field is directly proportional to the amount of electricalcurrent (amperage) flowing through the wire or cable; i.e., more amps = a strongermagnetic field.


In the field of electronics, EMI and RFIare synonymous—they both arise from elec-tromagnetic radiation, which is energy madeup of electromagnetic waves. These waves areclassified by their frequencies, aligned on aspectrum ranging from low to high: radiowaves, microwaves, infrared radiation, visiblelight, ultraviolet radiation, X-rays, and gammarays. The nature of electrical current is to emitelectromagnetic radiation. This energy becomesinterference when it causes unwanted signalsor noise to occur in other devices or circuitsthat are operating in or close to its frequencyrange.


STANDARDS ANDREGULATIONS

Most countries require that electronic andelectrical hardware work correctly even whensubjected to specified amounts of RFI, andthat they should not emit RFI that couldinterfere with other equipment. The U.S.Federal Communications Commission (FCC)has several applicable regulations addressingthese emissions. Manufacturers must test andlabel digital devices to inform end users of themaximum emission level from a product whenit’s used in accordance with its instructions.

The FCC has established two classes ofdevices. Class A equipment is intended for usein industrial or commercial areas. Class B,which is more stringent, includes residentialapplications as well as industrial applications. Asshown in the sidebar, the regulations include adisclaimer that must be stated in the instructionmanual, essentially stating that harmful interfer-ence, while prohibited, may occur anyway.

The electronics installation standards ofthe National Marine Electronics Association(NMEA) mirrors the FCC’s advice.

What the equipment manufacturers aren’ttelling you is that the FCC requirements wereintended to deal with issues related to industrialand residential interference migrating from onebusiness or household to another, and not forthe relatively close proximity of gear installedon boats! So even though these standards exist,we still run into problems on boats due to RFInoise and/or strong magnetic fields.

COMMON SOURCES ANDVICTIMS OF INTERFERENCE

Following are some of the most commonsources of EMI/RFI emissions on boats:

• AC generators• air conditioners

FCC-REQUIRED VERBIAGEFOR CLASS B DEVICES

This equipment has been tested and found to comply withthe limits for a Class B digital device, pursuant to part 15 ofthe FCC Rules. These limits are designed to provide rea-sonable protection against harmful interference in a resi-dential installation. This equipment generates, uses, andcan radiate radio frequency energy and, if not installedand used in accordance with the instructions, may causeharmful interference to radio communications. However,there is no guarantee that interference will not occur in aparticular installation. If this equipment does cause harmfulinterference to radio or television reception, which can bedetermined by turning the equipment off and on, the user isencouraged to try to correct the interference by one ormore of the following measures:

• Reorient or relocate the receiving antenna.• Increase the separation between the equipment and

receiver.• Connect the equipment into an outlet on a circuit dif-

ferent from that to which the receiver is connected.• Consult the dealer or an experienced radio/TV

technician for help.

• battery chargers• blower fans• DC-to-AC inverters• depth sounders• electric fuel pumps• engine alternators• engine ignition systems• engine starter motors• engine tachometers• fans• fluorescent lights• high-amperage wire runs (e.g., power

feeds to bow thrusters, anchor windlasses,and electric winches)

• lighting transformers• radars

8 9testing for electromagnetic and radio frequency interference

• shore-power isolation transformers• trim tab motors

That’s a fairly long list of culprits. Andwhat are the common victims of EMI/RFI?

• AM/FM stereos• audio systems• autopilot direction sensors (fluxgate

sensors)• computerized engine controls and their

wiring harnesses• flat-screen TV monitors• depth sounder transducer cabling• DGPS receivers• Loran-C receivers• magnetic compasses

Interference is caused by unwanted radio frequency energy. The energy is picked up by antenna systems and wiring cir-cuits and fed to receivers, which may not be able to distinguish between noise and signals if they share similar frequen-cies. (Reprinted with permission from Boatowner’s Mechanical and Electrical Manual, third edition, by Nigel Calder)

• microprocessors• SSB radios• TV and satellite tracking antenna direc-

tion sensors• VHF radios

So when equipment misbehaves, how dowe find the source of interference? I have twotools I like to use.

TOOLS OF THE TRADE

Even though EMI and RFI are considered syn-onymous, for the purposes of troubleshooting,I divide them into two categories: RFI, which Ican hear; and EMI, which I can’t hear, but Ican measure. I use two tools—one somewhatsophisticated, and the other extremely unso-phisticated—to search out the potential forEMI/RFI emissions to create problems. Tomeasure EMI, I use a gauss meter. To listen toRFI, I use a simple transistor radio. Using bothof these two tools is extremely easy.

Transistor Radio

Let’s start with the transistor radio. Pull out theantenna if it has one and turn up the volume ashigh as you can. Set it to the AM band andtune it to just off the scale, either high or low,so that no sound can be heard other than per-haps some low-level static. That’s it—now youare ready to try it out. Here’s how:

1 Turn on a battery charger or use the alter-nator on your car.

2 Gradually bring the radio closer to thecharger or alternator; you will clearly hearstatic getting louder and louder.

3 Move the radio back and forth and allaround the interference source to be sureyou don’t miss any leakage noise.


I use an AM/FM transistor radio that I picked up for $8at Wal-Mart to listen to RFI emissions in both the kHzrange and part of the MHz spectrum.

4 After you get the noise to peak, graduallymove the radio away from the source. Thedistance at which you no longer hear theinterference becomes the minimum safedistance (the separation distance or zone)from the unit that you should mount sen-sitive equipment.

5 Repeat this procedure with any interfer-ence source on the boat.

As we saw above, frequency matters, andon your transistor radio, the AM band you arelistening to is in the 540 kHz to 1,700 kHzrange. If you switch to the FM band and usethe same technique, you will be listening inthe 88 MHz to 108 MHz range.

You’ll only encounter interference prob-lems when the interfering frequency is fairlyclose to the frequency at which a given deviceoperates. What frequencies do boat appliancesrun at? Table 9-1 lists the operating frequenciesof some common marine electronic devices.The frequency range of the radio is closeenough to the frequencies of most onboardelectronics to reveal interference problems.

Once you’ve figured out where the inter-ference is coming from, turn to Chapter 12 tofind out how to minimize its effects.

Gauss Meter

The gauss meter is used in almost exactly thesame way as the transistor radio, except thatinstead of listening to the interference, you geta numerical readout in milligauss (mG). Forthe meter to measure the magnetic fieldstrength accurately, the device being measuredmust be pulling full current. As you move themeter closer to a device, the readings will

9 1testing for electromagnetic and radio frequency interference

To establish a safe RFI separation distance or zone froman alternator, move the radio around until the radio staticpeaks. Then gradually move the radio away from thatpoint until you no longer hear static. This is the minimumseparation distance.

Electronic Equipment Frequency

Cell phone 850 MHz or 1.96 GHzDepth sounder 50 or 200 kHzDifferential GPS 150—500 kHZGPS 1.5 GHzLoran-C 90—110 kHz AM radio receiver 540—1,700 kHzFM radio receiver 88—108 MHzSSB radio 2—22 MHzVHF radio 160 MHz

Operating Frequencies ofCommon Onboard Electronics

TABLE

9-1

This Sperry gauss meter has a range of 0.1 to 199.9 mG.

increase if interference is present, and decreaseas you move away. As with the radio, move themeter around, trying different angles, to deter-mine the peak of the interference, then moveit away from the device to find the minimumseparation zone.

I use a gauss meter to measure relative mag-netic field strength at various points around aconductor or piece of equipment, as well as to


EMF-200A, Sperry Instruments, www.awsperry.comModel 480823, Extech Instruments, www.extech.com

GAUSS METERS OR ELECTROMAGNETIC FIELD TESTERS

probe near large DC conductors and equipmentthat delivers high amperage to high-current-draw motors, such as starters and bow thrusters.It is a handy tool, costing about $100.

Using a gauss meter to check the separation zone near ahigh-current-draw cable from a battery switch. Notice thereading of 2.5 mG. The circuit in question (a bilge blowerfan) was drawing 6 amps, which is not a particularly highcurrent draw, but I wouldn’t mount a digital fluxgate com-pass sensor near this wire.

Here I used a small handheld compass to see how muchcompass deviation I could induce, and compared that tothe mG reading shown in the previous photo. A mere 2.5mG produced a 12-degree error on the compass. It took10 inches of separation before the compass returned tothe correct reading. By comparison, some battery charg-ers and inverters I’ve checked emit as much as 170 mG!That’s enough to send a compass into an extreme level ofdeviation from the actual heading. At a 170 mG reading,a typical separation zone would equate to 3 to 6.5 feet(1 to 2 m).

C H A P T E R

10Testing for ResidualCurrent and IsolatingIts Sources

In a perfect world, alternating current does just that: it alternates back and forth, and itdoes so evenly, between the hot and neutral conductors (or in the case of 240 VAC,between the L1 and L2 conductors). In effect, the current coming down the hot wire

should be exactly equal to the current flowing back down the neutral conductor. The cur-rents cancel each other out because they are perfectly balanced.

On many AC appliances, however, there is always a small amount of current leakage,also called residual current, which finds its way into the grounding conductor. For example:

• appliances with motors, such as refrigerators and air-conditioning units• appliances equipped with line noise filters, such as battery chargers and stereo

amplifiers• any device that uses power factor correction circuitry, such as, again, refrigerators and

air-conditioning units (see Chapter 5)

Additionally, as appliances age, materials such as heating elements and the windinginsulation in motors and generators gradually degrade. These conditions also cause resid-ual current.

In this chapter we will discuss both sources of AC leakage and how to test for it usingtwo instruments: a clamp-on AC leak tester and a megohmmeter.

AC LEAKAGE FROM APPLIANCES

Residual current from appliances is a normal situation and not dangerous as long as thelevel of leakage is maintained at an extremely low level. The International ElectrotechnicalCommission (IEC) limits acceptable leakage to 0.01 mA to 0.75 mA, depending on thespecific appliance. In the United States, Underwriters Laboratories specifications emulatethe IEC standard. Suffice it to say that acceptable leakage is limited to extremely low levels.

However, with multiple appliances on board, the normal leakage from each applianceadds up, and this cumulative leakage ends up traveling along the grounding conductor.Low-level AC current leakage begins to occur, allowing yet more AC current into thegrounding system. This is where the danger begins. This leakage is often well below the



Direct AlternatingCurrent (mA) Current (mA)

Effect Male Female Male Female

Slight sensation 1 0.6 0.4 0.3Perception threshold 5.2 3.5 1.1 0.7Shock, not painful, no 9 6 1.8 1.2

loss of muscular controlShock, painful, still no loss 62 41 9 6

of muscular controlShock, painful, “let go” 76 51 16 10.5

thresholdShock, painful and severe, 90 60 23 15

uncontrolled muscularcontraction, severebreathing difficulty

Shock, possible ventricular 500 500 100 100defibrillation following3 seconds of exposure

Effects of Electrical ShocksTABLE

10-1

WHY IS RESIDUAL CURRENT LEAKAGE SO DANGEROUS?

Residual current leakage into the water surrounding boats has risen to the top of the safety hazardlist in recent years because we now have indisputable proof that it has caused deaths in freshwaterlakes and rivers. The concern is not so great in salt water, because salt water is a good conductor ofelectricity, and any leakage current is rapidly dissipated to earth, either on the dock or the bottom.

Fresh water, however, is a rather poor conductor of electricity. As current leaks from the bottom ofa boat, a voltage gradient tends to stratify near the surface of the water, migrating sideways aroundthe boat and seeking a path to earth on the shore. Because the human body is composed of a veryhigh percentage of salt water, a swimmer who enters this voltage gradient and aligns his or her bodywith the gradient becomes a far more efficient current path than the water itself. Once exposed tothis current, a fatal heart muscle seizure may occur, and the swimmer is electrocuted.

How much residual current is potentially lethal? I use 30 mA as my baseline, simply because thatis the established standard everywhere in the world except North America. The 30 mA figure is lessthan the AC figures given for ventricular defibrillation in Table 10-1, but it has been established almostglobally as a reasonable compromise between protection devices tripping constantly and extremepain for humans. Anything above that limit is, as far as I’m concerned, simply too great a risk to take.

level it takes to trip a conventional circuitbreaker, nominally rated at 15 or 30 amps, butmore than enough to be lethal.

How much is lethal? Table 10-1 describesthe typical effects of exposure to DC andAC current on healthy humans (individualresponses will vary). Note that these figures arenot in amps, but in milliamps!

USING A CLAMP-ONAC LEAK TESTER

To protect against this potentially fatal prob-lem, we need to accurately measure very lowlevels of AC current leakage, in resolutions ofmilliamps. The amp clamp provided with thetypical multimeter does not have the requiredlevel of resolution; typically they can only readdown to a minimum of about 0.1 amp. A spe-cial tool is required, namely, a clamp-on ACleak tester, which can read down to 0.001 amp.

I use a Yokogawa clamp-on leak tester,model 300-31, for which I paid just over$400. Similar devices are available from othersuppliers, but I like this one because its clamphas a 40 mm inside diameter, which will fitaround the largest shore-power cords.

Before you begin using a milliamp AC leaktester, it is essential to understand that you willnow be measuring amperage in a way that mayseem dead wrong. Years ago, we were taught tomeasure amperage by connecting the meter inseries with the load, sometimes using a shunt.We also learned that we could check only onewire at a time. Later, as inductive amp clamps

9 5testing for residual current

became popular, we learned that you couldonly measure amperage by clamping one wireat a time.

Now, however, you will initially clamp yourmeter around a boat’s shore-power cord tocheck residual current. What’s being measuredhere? It’s the differential between what’s goingdown the AC hot wire and what’s coming backup the neutral conductor. This differential iscurrent leaking into the grounding conductor,measured in amps. If the reading is zero amps,then no leakage exists, and the hot and neutralare balanced perfectly, as they should be in aperfect situation. But if there is measurablecurrent, the question becomes, where is this

Model 300-31, Yokogawa, www.yokogawa.comModel 380942, Extech Instruments, www.extech.com

CLAMP-ON LEAK TESTERS

The Yokogawa model 300-31 AC leak tester.

current going, or, for that matter, where is itcoming from? That’s the tricky part, becausethe answer to the question is, it depends . . .

Electrical theory tells the electrician thatcurrent will always follow the path of leastresistance, which is essentially true. Therein liesthe problem. With a boat plugged into shorepower, there are multiple paths for residual cur-rent to travel. In a perfect world, residual cur-rent will travel down the grounding conductorand back to the power source somewhere at thehead of the dock. Unfortunately, it is not a per-fect world, and dock wiring problems are ram-pant. We cannot rely on the integrity of thedock’s grounding system (which is why I use aSureTest device to help confirm or deny thisintegrity—see Chapter 4).

Tracing the Source of Residual Current

Tracing the exact source of residual current is,unfortunately, a complex process. It requiresprocess of elimination, which can be exacting,tedious, and at times extremely inconvenient.


Use a milliamp AC leak tester to check residual current by clamping it around the shore-powercord. This reading of 6.62 mA is fairly low, but still more than desired. I prefer to see readingsof 3.0 mA or less.

I say inconvenient because the possibilityexists that another boat may be the source ofthe current, which is using the superiorgrounding (compared to the dock) of yourboat as the quickest path to the water. If that isthe case, then some of that current is surelyleaking out through the bottom of your boat.

The potential for current to leak into thewater is, ironically, related to ABYC standards,which call for the boat’s AC and DC ground-ing systems to be linked at the boat’s ground-ing bus or at the engine negative terminal. Ifthe AC grounding system on the dock hasexcessive resistance, some or all of the residualcurrent will exit the boat right through thebonded through-hull fittings as it seeks a pathto earth. In other countries, this bonding ofthe AC and DC grounding systems is not acommon practice, nor is it required underinternational standards. The reason is thatthey employ the 30 mA whole-boat protectionsystem, which will simply shut down the boatif the residual current hits 30 mA.

To locate the source, do the following:

1 Shut off the main AC breaker to the boat.If the residual current reading goes tozero, then it’s a fair bet the source of thecurrent leakage is on board the boat.

2 So next, turn the main breaker back on.

3 Then turn off the breakers to the boat’s var-ious branch circuits one breaker at a time.

4 If the current reading suddenly goes tozero when you turn off a breaker, you’veidentified the problem circuit. Most often,the leakage current is coming from anappliance on the circuit, and the applianceitself may warrant further testing to checkfor leakage right at the device.

5 If turning off breakers and switches pro-duces no change in the residual current atthe shore-power cord, then the source ofthe leakage current is another boat pluggedinto the same shore-power circuit.

6 Try to isolate the problem by unpluggingeach boat at the dock, one by one (seebelow).

7 If the reading on your amp clamp goes tozero, you’ve found the culprit.

It’s also likely that the reading may get dra-matically lower but not drop to zero becausethere is a real possibility the source of leakageis more than one boat, and that what you arereading on your meter is the cumulative leak-age of multiple faulty boats. To protect yourboat, you may need to gain access to severalothers. Did I mention inconvenience?

Since you can’t just turn off the power toeverybody’s boat without getting permission,I generally notify the marina operator that aserious safety problem exists that needs imme-diate attention. The manager should immedi-ately prohibit swimming from the docks untilthe problem is resolved, and if the marina


operator is serious about customer service andcustomer safety, he or she will promptly grantyou the permission you require. If you need tomake your case more strongly, report yourown leakage test results in the context ofTable 10-1, which shows the very low levels ofcurrent capable of causing death.

Measuring Voltage Potential

Although you can’t measure current flowthrough the water by any simple method, youcan measure voltage potential. We are actuallymore concerned about voltage potential any-how. In this case, we are concerned about elec-trical shock hazard and voltage potentialapplied to human bodies as they swimthrough the water. The actual current flowthrough the body will vary depending on theperson, and factors such as skin resistance andhow long the person has been in the water willdetermine actual current exposure. All youneed to test this is a conventional DVOM setto the VAC scale and an extended lead for thehot terminal. Additionally, a broomstick isquite helpful to make an extension probe forthe meter (see the sidebar on page 98). Withthese tools, follow these steps:

1 Confirm the integrity of the ground withthe SureTest tool.

2 Attach the hot lead of the DVOM to theend of the broomstick, leaving the con-ducting tip exposed.

3 Plug the meter’s other lead into thegrounding terminal on the shore-powerpedestal.

4 With the meter set to VAC, probe thewater around the dock and boat lookingfor a VAC reading.

5 You won’t see a solid 120 or 220 VACreading, but you could easily see 60 to100 VAC if a problem exists. If that’s thecase, immediately notify the marina

operator and all the boatowners in thearea—a potentially deadly situation exists.(Note: Your previous residual currentreadings and SureTest readings are clues tothis possibility. Take these clues very seri-ously; you could save somebody’s life.)

AC LEAKAGE FROMDEGRADED INSULATION

The second common cause of residual currentis the breakdown of insulation in motor andgenerator windings and in shore-power isola-tion transformers. Leakage can occur between


adjacent windings and between the windingsand case grounds. It can also be influenced byambient temperature and humidity. However,this breakdown can be difficult to detectbecause the insulation may still retain most ofits insulating properties, and the device maycontinue to function normally even as theleakage is occurring.

The effectiveness of insulation is a func-tion of its resistance (impedance), measured inohms (�). Materials that are used as insula-tion of course have very high impedance—sohigh, in fact, as to be off the scale of the ohm-meter function on a standard DVOM, even

MAKING AN EXTENSION PROBE

To make an extension probe, you’ll need the following supplies:

broomstickcrimp-on ring terminalseveral small screwssquare of copper flashingextended multimeter lead

To begin, remove the pointed probe end common to most meter leads and attach the crimp-on ring terminal. Theterminal should have a hole in it for the small screw you’ll use to attach the copper plate.

You can get copper flashing at your local hardware store. (Home Depot sells 5-by-7-inch precut pieces that arejust right for this job.) The actual size isn’t critical, but bigger is better since it makes the lead more sensitive to findingcurrent fields.

Use small screws to attach the copper square to the lead and secure it to the end of the broomstick handle.

extended lead black lead (plugs intothe grounding terminalon the shore-powerpedestal)

meter copper square(goes in water)

Here’s the extended probe rig I made.

after they have begun losing their effective-ness. This is not surprising, since ohmmetersare typically used to look for failures of con-ductivity, not of insulation.

Enter the megohmmeter, commonly knownas a megger. The megger is used to measure highresistance values in insulation in the mega,or millions-of-ohms, range (1 megohm =1,000,000 ohms). The model I use (an Extech380360, which costs just under $200) can readup to 2,000 M�, or 2 billion ohms. That is veryhigh resistance.

Caution: Be extremely careful whenusing a megger; it can destroy circuitry andcause personal injury or death. As with otherinstruments we’ve covered, the megohmmetersends a signal through the circuit—only in thiscase, it’s anywhere from 250 to 1,000 volts! (Incontrast, the typical DVOM set to the ohmsscale sends only about 1 or 2 volts through thecircuit.) This amount of voltage can do somedamage—not only to sensitive electronic con-trol circuitry but to you.

Because of its powerful capabilities, theuse of a megger has some limitations andprecautions:

• Only use a megger on heavy-gauge wirewinding sets.

• Only use a megger when the manufac-turer of the equipment specifies the use ofone as a test method and provides instruc-tions on how to isolate any circuitry asso-ciated with the windings.

• Only perform megohmmeter tests withthe equipment workshop manual in

hand, and follow the manufacturer’s testprocedure and specifications to the letter.

The specification I use regularly is a mini-mum of 1 megohm, which is based on gener-ally accepted U.S. military and TransportCanada guidelines for ships and large “rotatingmachinery,” as they often refer to generators,and is their minimum requirement.

A megohmmeter test is often timed, as ittakes a while for the windings to become “sat-urated” as the high voltage is applied. In amaintenance situation, technicians may use amegger to periodically test for gradual deterio-ration of insulation over specified time inter-vals, so extended tracking and data logging issometimes necessary. For most recreationalboat applications, however, this sort of work isquite uncommon, as the labor costs will typi-cally outweigh the cost of simply replacingcomponents.

So when do I use a megger? If I get higherthan normal residual current readings from aboat’s shore cord, for example, and I am able totrace the leakage to a particular circuit, I usethe megger to further isolate the problem.If the circuit feeds a refrigeration system, thenthe compressor motor windings are suspect. Ifexcessive leakage is detected from a shore-power-supplied battery charger, its transformerwindings may be the problem. If residual cur-rent is only noticed when the AC system isbeing supplied by an onboard generator, thenits windings may be at fault. All of these prob-lems may be caused by insulation breakdown,and a megger might be the best tool to confirm


Model 380360, Extech Instruments, www.extech.comModel 1026, AEMC, www.aemc.com

MEGOHMMETERS

or reject that suspicion. Alternatively, manypeople will use the clamp-on leak tester dis-cussed earlier. If excessive leakage is found,they’ll just replace the piece of equipment.

USING A MEGOHMMETER

Meter lead connections and screen displaysvary from one brand of megger to another, butthere are some commonalities among meters:

• multiple voltage test ranges• a low ohms scale for checking continuity

and resistance values below 200 �• the ability to measure voltage up to 600

VAC• a “3-minute” lock test function (a com-

mon time parameter used by equipment

manufacturers who recommend periodicinsulation tests)

It is common practice to select a voltagerange that is approximately twice the value ofthe rating of the appliance or cable beingtested:

• For a 120 VAC appliance, use the 250 Vscale (or the nearest equivalent on themeter).

• For a 220 VAC appliance, use the 500 Vscale.

• For 600 V boat cable, use the 1,000 Vscale.

Connecting the meter to the circuit orappliance in question is easy once you’vesorted out any isolation requirements and

1 0 0 electrical systems troubleshooting

multiple voltagetest ranges

positive test lead

negative test lead

master test button

3-minute locktest function

The Extech 380360 megohmmeter measures resistance up to 2,000 M�. It also has a 3-minute lock test func-tion. Also shown is the unit’s master test button.

other specified criteria, such as temperature.For example, if you are testing cable insulation,make sure the cable is completely disconnectedfrom the circuit it serves at both ends. Forground leakage tests on a tool or appliance,there are no special concerns to address. But formotor circuits, transformer windings, and gen-erator winding sets, it’s best to follow the adviceof the equipment manual to ensure that youdon’t do more harm than good. As for tempera-ture concerns, some equipment is tested at nor-mal operating temperatures. In other cases, theequipment manufacturer’s test procedure mayrequire you to adjust the effective resistancevalue up or down based on actual temperature.

Even with a maximum measurement rangeof 2,000 M�, it’s not uncommon for amegohmmeter to max out during testing.

Different models indicate this in various ways;on the Extech model 380360, off the scale isindicated by a screen display of 1 followed byblank spaces, a decimal point, and the symbolM� (see photo page 102). This simply meansyou have excellent insulation—it’s not an error.

VALUE AND UTILITY

Meggers can be extremely useful, but therange of applications for most marine techni-cians and boatowners is quite limited, andmost technicians do not use them very often.Unless you work on mega- or superyacht-sizedvessels, or in an industry where leakage andresistance checks are regularly required, aclamp-on leak tester will supply most of yourneeds.

1 0 1testing for residual current

transformerprimary

winding lead

chassis groundshould beelectricallyisolated

Testing for leakage and good ground isolation on a transformer winding set. Notice the meter lead connections at boththe transformer and at the meter end. The stud on the motor is the ground. The meter’s other lead is clipped to one of theprimary winding leads.


To test a piece of coaxial cable for leakage, insert thelead between the core conductor and shield.

C H A P T E R

11A Basic Corrosion Survey

In this chapter, we will look at some of the tools and procedures we use to conduct abasic underwater metal corrosion survey. These procedures typically fall into a special-ized subcategory in the marine service world, that of a corrosion specialist. (In fact, one

of the certifications that the ABYC offers is for corrosion. Interestingly enough, the ABYCalso strongly recommends that those who sit for this certification have the ABYC Electri-cal Certification as a prerequisite.) Underwater metal corrosion can be caused by failuresor improper installations of electrical systems, however, so general marine electricians anddedicated do-it-yourself boatowners should at least be aware of the basics of the subject.Those who wish to delve further should contact the ABYC’s Education Department andregister for a Corrosion Certification course and exam.

My goal in this chapter is to provide you with enough knowledge to perform abasic corrosion survey, which will include looking for stray DC current caused eitherby faulty wiring or defective DC appliances. I will also cover the galvanic isolatorand how to determine if it is in good working order. Since a galvanic isolator may bean integral part of the boat’s AC grounding system, its proper functioning is criticalto crew safety.

TOOLS OF THE TRADE

The corrosion specialist uses a variety of arcane equipment, special reference electrodes,conductivity testers, water pH and salinity testers, split-out shore cords, prewired galvanicisolators, extra anodes of different materials, and an absolute plethora of gear to do his orher work.

However, for the marine technician and advanced boatowner, I’m going to focus ontwo specific tools: a silver/silver chloride reference electrode and an extremely high resolu-tion DC amp clamp, such as the one shown in the photo on page 117. In addition, youwill need your standard DVOM.

A special electrode is necessary because (1) we will be measuring extremely small volt-age potentials; (2) we will need extremely high levels of sensitivity and precision; and (3)we must be able to repeat the test in a variety of electrolytes (i.e., water of various degreesof salinity). The silver/silver chloride electrode meets all these requirements; it is the mostcommon reference electrode used in marine applications due to its ease of manufactureand its stability over a wide range of temperatures.


Many technicians prefer to use a commonzinc electrode as a reference cell, and zinc willwork. However, I prefer to use a silver/silverchloride cell because ABYC Standard E-2,Cathodic Protection, bases all its voltagepotential values on the silver/silver chloridecell (see the table on page 106). If you chooseto use a different reference electrode, the stan-dard does provide conversion tables. In thecase of zinc, you would add 1 volt to yourmeter reading to convert to the values in


Standard E-2. Personally, I find this all ratherconfusing and prefer not to deal with conver-sions in a working situation.

UNDERWATER METALCORROSION ANDPROTECTION BASICS

A basic corrosion survey tests the electricalpotential of your boat’s hull (the metal) toanswer two questions:

DVOM

connectinglead

silver/silver chloridereference electrode

A conventional DVOM and a silver/silver chloride reference electrode. This one is made by USFilter (nowcalled Siemens Water Technologies) under the trade name Capac, but the cells are readily availablethrough Mercury engine special tools catalogs or West Marine. The electrodes cost about $85. The Capacunit costs about $250 and is equipped with an extremely long connecting lead for use on larger boats.

Capac, Siemens Water Technologies, www.usfilter.comModel 20008, ProMariner, www.promariner.com

SILVER/SILVER CHLORIDE REFERENCE ELECTRODES

1 Is the boat’s cathodic protection system(assuming it has one) doing its job?

2 What is the overall condition of the boat’sbonding system?

First, let’s review the difference between acathodic protection system and a bondingsystem. Simply put, a cathodic protection systemprotects a boat against galvanic corrosionthrough the use of zinc anodes. A bonding systemprotects the boat against stray-current corrosionby electrically tying together all the metals onthe boat and then connecting the bonding wiresto the boat’s common ground point.

Cathodic Protection andGalvanic Corrosion

When two dissimilar metals are immersed inan electrolyte, their differing electrical poten-tials will produce a voltage difference. Any-time a connection is made between these twometals, an electrical current will flow from thehigher-voltage metal (the cathode) to thelower-voltage metal (the anode), leading tothe deterioration of the anode. Since the cath-ode in a galvanic cell does not dissolve, it isalso referred to as the most noble metal, whilethe anode is referred to as the least noble.Note that this relationship is relative; depend-ing on its position in the galvanic series table(see page 106), a metal will be cathodic withrespect to metals that have a lower electricalpotential but anodic with respect to thosewith a higher potential.

Applying this to boats and the marine envi-ronment, it’s clear that since metal fittings andcomponents on boats are made of dissimilarmetals and are usually underwater, you havethe makings of a galvanic cell on your boat.Add an electrical connection, and galvaniccorrosion will result.

Cathodic protection is the answer to basicgalvanic corrosion. By installing zinc anodes

1 0 5a basic corrosion survey

on your boat, you provide an anode that willbe consumed (sacrificed) to protect the boat’smetal fittings and components.

The scenario becomes a bit more compli-cated when you hook up to dockside power.Now the external circuit becomes the greengrounding wire, which basically connectsevery boat to one another. As a result, youcould find your boat becoming the cathodicprotection for your neighbor’s boat, and all ofyour zinc anodes will start corroding veryquickly. Once they are gone, the next leastnoble metal on your boat will follow.

The solution to this problem is a galvanicisolator. Basically, this device interrupts thecircuit between your boat and the otherboats tied into the dockside power. It has apair of diodes that block low DC voltage, upto 1.5 V, but allow higher AC voltage topass, which is an important feature becauseas mentioned in Chapter 10, even low-levelAC voltage in the water is a danger to swim-mers. Thus while providing a solution to gal-vanic corrosion, the galvanic isolator alsoprovides protection from dangerous ACvoltage.

Bonding and Stray-Current Corrosion

Stray currents can come from faulty electricalcircuits or from any situation that provideselectrical current with a path that has a lowerresistance to ground than the appropriate oneback to the battery. For example, if you have aconnection sitting in a puddle of water, thewater provides a path of lower resistance thanthe wire going back to the battery. As this cur-rent follows its path of least resistance throughmetal into the water, it will corrode the metal.It doesn’t matter if the metal is more anodicor more cathodic (zinc anodes won’t workhere)—the current will corrode the metal, andthe direction of the current flow determineswhich metal will corrode.

Range of Corrosion Potential (relative to silver/silver chloride

Metals and Alloys half cell; volts)Ca

thod

ic o

r Mos

t Nob

le (P

assi

ve)

Anod

ic o

r Lea

st N

oble

(Act

ive)

Magnesium and Magnesium Alloys –1.60 to –1.63

Zinc –0.98 to –1.03

Aluminum Alloys –0.76 to –1.00

Cadmium –0.70 to –0.73

Mild Steel –0.60 to –0.71

Wrought Iron –0.60 to –0.71

Cast Iron –0.60 to –0.71

13% Chromium Stainless Steel, Type 410 (active in still water) –0.46 to –0.58

18-8 Stainless Steel, Type 304 (active in still water) –0.46 to –0.58

Ni-Resist –0.46 to –0.58

18-8, 3% Mo Stainless Steel, Type 316 (active in still water) –0.43 to –0.54

78% Ni/13.5% Cr/6% Fe (Inconel) (active in still water) –0.35 to –0.46

Aluminum Bronze (92% Cu/8% Al) –0.31 to –0.42

Naval Brass (60% Cu/39% Zn) –0.30 to –0.40

Yellow Brass (65% Cu/35% Zn) –0.30 to –0.40

Red Brass (85% Cu/15% Zn) –0.30 to –0.40

Muntz Metal (60% Cu/40% Zn) –0.30 to –0.40

Tin –0.31 to –0.33

Copper –0.30 to –0.57

50-50 Lead/Tin Solder –0.28 to –0.37

Admiralty Brass (71% Cu/28% Zn/1% Sn) –0.28 to –0.36

Aluminum Brass (76% Cu/22% Zn/2% Al) –0.28 to –0.36

Manganese Bronze (58.5% Cu/39% Zn/1% Sn/1% Fe/0.3% Mn) –0.27 to –0.34

Silicon Bronze (96% Cu max./0.8% Fe/1.50% Zn/ 2.0% Si/0.75%Mn/1.60% Sn)

–0.26 to –0.29

Bronze Composition G (88% Cu/2% Zn/10% Sn) –0.24 to –0.31

Bronze Composition M (88% Cu/3% Zn/6.5% Sn/1.5% Pb) –0.24 to –0.31

13% Chromium Stainless Steel, Type 410 (passive) –0.26 to –0.35

90% Cu/10% Ni –0.21 to –0.28

75% Cu/20% Ni/5% Zn –0.19 to –0.25

Lead –0.19 to –0.25

70% Cu/30% Ni –0.18 to –0.23

78% Ni/13.5% Cr/6% Fe (Inconel) (passive) –0.14 to –0.17

Nickel 200 –0.10 to –0.20

18-8 Stainless Steel, Type 304 (passive) –0.05 to –0.10

70% Ni/30% Cu Monel 400, K-500 –0.04 to –0.14

18-8, 3% Mo Stainless Steel, Type 316 (passive) 0.00 to –0.10

Titanium –0.05 to +0.06

Hastelloy C –0.03 to +0.08

Platinum +0.19 to +0.25

Graphite +0.20 to +0.30

The galvanic series table. (Reprinted with permission from Boatowner’s Mechanical and Electrical Manual, third edition, by Nigel Calder)

Bonding electrically ties together all majorfixed metal items and then connects them tothe boat’s ground. This has two purposes:

1 It removes the conditions for current toflow. The key to inducing electrical cur-rent flow in metals is a difference in volt-age potential. If there is no potential dif-ference, there can be no current flow. Byelectrically tying all of the underwatermetals together, we create an electrical cir-cuit where no potential difference exists,therefore no current will flow. No currentflow, no corrosion.

2 It removes the possibility of an inappro-priate path to ground, such as through the

hull or through-hull fittings. Bondingmaintains a low-resistance path back tothe battery.

In the United States, the bonding approachis commonplace. Underwater metals con-nected via a bonding system will polarize (seebelow), and as long as they are connected toan appropriately sized anode—either zinc, alu-minum, or magnesium (depending on thelocation of the vessel)—the anode will becomethe sacrificial lamb in terms of corrosion. Oneargument against this approach concerns out-side forces, such as current leaks in the waterat a dock that can migrate and be distributedvia a bonding system inside the boat. So somebuilders believe isolating the metals is a better


*the single point at which all the bonding and grounding circuits are tied together

DCequipment

accessorynegative bus

overcurrentprotection

branch circuits

distribution panelor switchboard/panelboard windlass

DCnegative bus

floatswitch

bilgepump

parallel switchor solenoid

mainfeed

batteryswitch

housebattery

batteryswitch

engine generator(AC or DC)

batteryswitch

battery enginenegativeterminal

DC mainnegative bus*

battery

AC grounding busfueltank grounding

busbonding cable

chainplates

seacock

strainer

metal objectsmain lightningdown conductor

electronicsground plate zinc

immersed ground plate or strip

current-carrying

normally non-current-carrying

chainplates

A bonding system. (Reprinted with permission from Boatowner’s Mechanical and Electrical Manual, third edition,by Nigel Calder)

approach. Many European boatbuilders takethis approach. In the United States, we favorbonding; the ABYC advocates bonding, andI support that position for most (but not all)boats.

In some cases, bonding is just not practicalor necessary. For example, small trailerableboats with only a few through-hull fittingsaren’t really a concern. They can be easily mon-itored, and if the boat spends most of its lifesitting on a trailer, bonding is overkill. Forwooden boats, bonding may not be a greatchoice either; faulty cathodic protection sys-tems on wooden hulls can wreak havoc withthe wooden structure of the boat.

CONDUCTINGA CORROSION SURVEY

Most corrosion surveys are performedbecause the boatowner is having a problem:either excessive corrosion or, more commonly,rapid anode consumption. Troubleshootingthe problem requires first gathering somedata: water temperature, current, depth, andsalinity; boat usage; and the presence of newboats in the area. These can all impact howlong an anode lasts, and you (or, in com-plex cases, a corrosion specialist) will spendquite a bit of time researching changed con-ditions when the complaint is rapid anodeconsumption.

For the purposes of this book, we’ll confineourselves to learning how to answer a few basicquestions:

• Is the boat cathodically over- or under-protected?

• Is the boat equipped with a galvanic isola-tor? If so, is it functioning properly?

• Is there any electrical current leakage intothe bilge water or the bonding system? Ifso, which circuit is causing this inducedcurrent?

We’ll begin by confirming the calibrationof the DVOM; it should be correct to withinless than 50 millivolts (mV). We will bemeasuring very small values, and sensitivity isquite important.

Here’s how to check calibration using azinc anode and a silver/silver chloride refer-ence electrode:

1 Using a small-engine pencil zinc anode asyour test piece, attach it to your DVOM’spositive lead.

2 Connect the silver/silver chloride refer-ence electrode to the DVOM’s “com” ornegative jack (top photo opposite).

3 Set the meter to DC volts and submergethe zinc and reference electrode in saltwater. Be sure the electrodes are nottouching the bottom; 1 foot or so belowthe surface is just right. The reference celland the zinc anode should be within sev-eral feet of each other.

4 The meter should read approximately–1 volt DC (bottom photo opposite),indicating that the meter is calibratedcorrectly. A reading of 50 mV or so oneway or the other indicates the zinc alloyvaries slightly, which changes its actualvoltage potential.

5 If your meter readings are not approxi-mately –1 VDC, try another anode; theone you are using may not be zinc, butrather magnesium or an aluminum alloy.

6 If a new anode doesn’t help, see if anotherDVOM makes a difference. If it does,then your meter is at fault.

It’s important to note that the voltagepotentials given here assume you are workingin a saltwater environment. In fresh water, dueto its relatively low conductivity, voltagepotentials will be much lower. For example, a


boat in salt water that might give a hull poten-tial reading of approximately –550 mV to–900 mV would only give a reading of –300 mVto –400 mV in fresh water. Of course, thereading you get will depend on the actual con-ductivity of the water the boat is floating in.

Corrosion specialists that work in freshwa-ter environments regularly use a copper sulfatereference electrode to help offset this conduc-tivity disparity. A copper sulfate electrode typ-ically reads about –100 mV higher than asilver/silver chloride electrode, keeping actualreadings more in line with acceptable protec-tion levels as described in ABYC StandardE-2. A good source for copper sulfate refer-ence electrodes is the M. C. Miller Company,www.mcmiller.com.

Follow these steps to measure a boat’s basichull potential:

1 Ensure all normal dock connections are inplace (e.g., shore power, cable TV, etc.)

2 Plug the reference electrode into yourDVOM’s “com” or negative jack, andsubmerge it in the water; don’t let theelectrode touch bottom—about mid-draftfor the boat works here.

3 Touch the DVOM’s positive lead to eitherthe boat engine’s negative terminal or theprimary grounding bus bar behind themain electrical distribution panel.

4 The voltage reading on the DVOM repre-sents the hull’s basic potential. It shouldbe a negative number similar to thoseshown in the galvanic series table (seepage 106).

The actual reading you get will be anaverage of the potentials of all of theunderwater metals connected to thegrounding system as compared to thereference electrode. This “average” iswhat happens once metals are connected


pencil zincanode

negativelead

DVOM

silver/silverchloridereferenceelectrode

To check the test instrument prior to conducting an underwater corrosionsurvey in salt water, clip a pencil zinc to the meter’s positive lead andattach a silver/silver chloride reference electrode to the negative lead asshown.

With both leads in the water off the side of the dock (just outside thephoto), the meter should read approximately —1 VDC, as shown.

(via a bonding system) and submerged inan electrolyte. This is an electrochemicalprocess called polarization, in which theinherent potential of the various bits ofsubmerged metal changes, and they beginto equalize, or come to a common average

potential. The idea is to make sure thatthe potential reading you get with ananode (or anodes) attached to the systemis at least –200 mV greater (more nega-tive) than the average reading without ananode attached. Actual numbers will varydepending upon the number and surfacearea of the anodes, as well as the specificalloy the anodes are made of.

5 Compare your readings to the recom-mended values in ABYC Standard E-2,shown opposite, to see if your boat is ade-quately protected.

The reading in the bottom photo oppositeis slightly more negative than the ABYC tablesuggests. This is not unusual and representsno problem in the case of a fiberglass boat. Allthat is implied is that the anode surface area isslightly greater than needed, and since theboat being tested just recently had its anodesreplaced, this is to be expected. As the anodesare depleted, the exposed surface area will be

reduced and the voltage potential will becomemore positive. In fact, I generally recommendadjusting the anode area to give a slightlymore negative reading than the ABYC tablesuggests as a starting point, knowing that in arelatively short period the numbers will fallwithin the prescribed range. All this does ineffect is increase the effective service life of theanodes by a few weeks or a month.

What if your readings do not fall withinthe ranges recommended by the ABYC E-2standard?

If the readings are less negative than rec-ommended, your boat does not have adequateanode surface area exposed to the electrolyte inwhich it is floating. There are two explana-tions for this scenario:

1 If the anodes have been doing their job forthe better part of a boating season, thenthe situation is normal. The decrease insurface area means the zinc material hasbeen sacrificing itself (eroding) to protect


12V 0V

Through-hull

Radio

Groundplate

Bonding

Zinc

Commonground

Battery

Silver-silver chloride

electrode

Digital multimeteron DC volts

Testing your boat’s corrosion potential. (Reprinted with permission from Boatowner’s Illustrated Electrical Handbook,second edition, by Charlie Wing)

your valuable metal components. It’s timeto replace them.

2 If the anodes were replaced recently, thenthe rapid loss of material means that youmay never have had enough anode mate-rial to begin with, or that your anodes areprotecting other boats on the dock due toa lack of a galvanic isolator, or that AC orDC stray currents may be at work.

If the readings are more negative than rec-ommended, there are two possibilities:

1 It is possible someone has inadvertentlyinstalled magnesium anodes. These areused in fresh water and should never beused in a saltwater environment as theirnegative potential is high enough to createan overprotection situation that can bevery damaging to aluminum hulls andoutdrives. (Aluminum is unique amongthe common metals used in marine con-struction in that it can be damaged byeither under- or overprotection from acathodic protection system.)

2 There is a DC current leak, either through aconnected fitting on the boat or from anadjacent boat—via the water—that has aDC stray-current problem. (We’ll look athow to check for this shortly.) If the currentleak is coming from someone else’s boat,call a corrosion specialist as it’s going totake some serious tracking down to isolate.


enginenegativeterminal

and meterlead

Touch the meter’s negative (“com”) lead to the batterynegative return, or engine negative terminal, as shown.

The recommended range of cathodic protection from ABYC Standard E-2. (Courtesy ABYC)

A typical meter reading, —0.955 mV, for a fiberglass boatwith bronze running gear and a typical array of bronzethrough-hull fittings.

Let’s assume the reading you get is withinthe prescribed range. You’re not done yet:

1 With your meter still connected and thereference electrode still submerged,remove the electrical connections fromthe boat to the dock one at a time andwatch for a change in the meter readings.

2 If the reading gets more negative, thenthere was leakage from the boat to thedock through the shore cord you just dis-connected. The subject boat may be help-ing to protect other boats at the dock withits anodes.

3 If the reading gets less negative when dis-connected, there may be a DC stray-current problem on board the boat.Further checking will confirm or denythis possibility.

4 If there is no change in the reading withthe boat plugged in versus not plugged in,two possibilities exist:

• The most likely reason is the boat hasan isolation transformer or galvanic iso-lator that is doing its job.

• There is a no-ground situation at thedock—a potentially deadly situation. Itis essential that you check the integrityof the dock ground with the SureTesttool (Chapter 4).

Next, let’s test the integrity of the bondingsystem on board the boat. We’ll use theDVOM to check the hull potentials:

1 First, perform this test with the engine(s)off.

2 Find all the metal objects in the bilge thatare attached to the bonding system.

3 With your reference electrode still inthe water near the boat, use yourpositive meter lead and check the


Checking potential at a seacock (touch the lead to anymetal part). The meter reading is within 1 mV of the over-all hull potential shown in the bottom photo on page 111,indicating that all is well.

potential at each bonded metal fittingone by one. The readings should be thesame, or within about 50 mV of thebasic hull potential; otherwise, thepossibilities are:

• If a reading is more positive than thebasic hull potential, a poor connectionin that leg of the circuit is indicated, andit should be tracked down and repaired.

• If a reading is dramatically more posi-tive or negative than the basic reading,it may indicate DC stray current,which should be remedied.

4 Now repeat the test with the engines run-ning. Dramatic changes in the readingsmay indicate DC stray-current problemsinduced by something electrical that is run-ning on the engine, typically an alternator.

Finally, we need to check the dock’s potential.For this, we’ll move to the shore-power pedestal:

1 With the reference electrode still in thewater, plug the DVOM’s positive lead intothe ground lug on the dock receptacle.

2 Caution: A shock hazard exists. Be sureyou have positively identified the groundlug at the pedestal, not the hot lead. On30 amp service, this is typically the notchedor L-shaped lug. On 50 amp service, it is ashell connection, as shown in the photo.See the illustrations for other commonshore-power terminal configurations.

3 Most docks will read between –400 mVand –800 mV. A reading outside that


shell

positive lead

The shell is the ground connection on a typical 50 amp shore-powerreceptacle.

100A, 120/240VPin and sleeve3 pole, 4 wire

50A, 120/240VLocking

3 pole, 4 wire

30A, 120/208V 3ØYLocking

4 pole, 5 wire

100A, 120/208V 3ØYPin and sleeve4 pole, 5 wire

240 and 208 Volts

Receptacle

Plug

Receptacle

Plug

Receptacle

Plug

Receptacle

Plug

W

WG

G

W

G

Y X

XZ

Y

G

Y

X

X

Z

WY

G

W

YX

G

W

XY G

WZ

YX

G

WZ

YX

15A, 120VStraight blade2 pole, 3 wire

20A, 120VStraight blade2 pole, 3 wire

20A, 120VLocking

2 pole, 3 wire

30A, 120VLocking

2 pole, 3 wire

50A, 120VLocking

2 pole, 3 wire

120 Volts

Receptacle

Plug

Receptacle

Plug

Receptacle

Plug

Receptacle

Plug

Receptacle

Plug

G G

G G

W W

W W

G

W

G

W

G

W

G

W

WG

W G

Dock and shore-cord terminal configurations, from ABYC Standard E-11. (Reprinted with permission fromBoatowner’s Illustrated Electrical Handbook, second edition, by Charlie Wing)

range could indicate DC stray currentmigrating through the dock ground sys-tem. This will require investigation.

4 Assuming the dock’s basic potential isbetween –400 mV and –800 mV, com-pare that number to the boat’s basicpotential both when plugged into thedock and when unplugged.

5 The basic hull potential with the boatplugged in should fall between the basicdock potential and the boat’s unpluggedpotential. Although the exact reading for theunplugged boat may not be the ideal valuefor the specific boat you are checking, it maybe acceptable if anode consumption iswithin the acceptable service limits of threeto ten months for a typical recreational boat.


Proper electrical location of a boat’s galvanic isolator, from ABYC Standard A-28. (Courtesy ABYC)

Galvanic Isolators

As mentioned above, each boat plugged in at adock is helping to protect all the other boats atthe dock. They are all married to one anothervia the green wire. For this reason, I stronglyrecommend a galvanic isolator for any boatthat spends its time plugged in at a dock.

The proper location for the galvanic isola-tor is in series with the green grounding conduc-tor, and as close to the AC inlet on the boat aspossible. Install it so that it can’t be bypassedelectrically, as shown in the illustration opposite.

You may need to test the galvanic isolatorto ensure that it is functioning properly. AnABYC-compliant isolator is made up of twosets of opposed diodes and a parallel-connected capacitor (exclusive of any status-monitoring circuitry that may be associatedwith the device), as shown in the detail in theillustration. You must confirm continuity forcurrent flow in both directions to rule out a caseshort to ground of one or more of the diodesand to ensure the capacitor is functional.

Testing a Galvanic Isolator

In most cases, this test is a three-part process,as outlined below.

Step 1. Check the continuity of thediode set in one direction:

1 Connect your DVOM leads to the termi-nals where the boat’s green wires attach.It doesn’t matter which lead connects towhich terminal; you will be checking cont-inuity in two directions through the device.

2 Set the DVOM to the “diode” testfunction.

3 With the leads connected, watch as themeter’s reading gradually increases, showingthat the battery in your DVOM is chargingthe capacitor inside the galvanic isolator.

4 If you get an immediate continuityreading through the isolator and no


gradual increase in your reading, then theisolator is not equipped with a capacitorand is not compliant with current ABYCstandards.

5 Assuming the isolator has a capacitor, waituntil the numbers on the DVOM stopincreasing (this may take a few minutes).Make a note of the number.

Step 2. Check the continuity of thediode set in the opposite direction:

1 Disconnect the meter leads and “flash” thetwo terminals on the isolator to dischargethe capacitor.

2 Reverse the meter’s leads from the previousconnection and repeat the Step 1 test above.

3 If the capacitor is in good condition, themeter reading should stop within 10% to15% of the value from Step 1.

If you get a no-continuity reading fromeither test, the isolator diode sets have failed to

Checking the continuity of the diode set in one direction. A grad-ual rise in the reading indicates the charging of the capacitorfrom the battery of the DVOM. Once charged, the meter readingwill stabilize. The reading is essentially the amount of voltagedrop across the isolator——typically around 0.9 volt.

1

galvanic isolators can be used to effectivelyblock galvanic currents up to about 1.4 V. Byputting two diodes in series, you can block 1.4VDC. Galvanic isolators with capacitors aredesigned to offer extra protection for thediodes in the event of a continual, low-level ACleakage current running through the groundingwire. This is not uncommon, as discussed inChapter 10. AC passes through a capacitor; DCwill not. The capacitor provides a path for anyAC leakage, or fault current for that matter, tobypass the diodes, but still effectively blocksDC current flow. When we discuss galvaniccurrent, we are referring to direct current.

Tracking Stray Current

So far we’ve only touched briefly on stray cur-rent, and evidence of its existence is based onvarious hull or dock potential readings withthe silver/silver chloride reference electrode(excessively high negative meter readings canindicate DC stray current). Stray current iswhat I like to refer to as battery-level voltageand current, as compared to the galvanic currentwe have been talking about up to this point—voltages less than 1.4 VDC.


an open circuit and immediate replacement isneeded.

Step 3. Determine if a short circuit toground exists:

1 Connect one meter lead to either of thegreen wire terminals and the other lead tothe isolator case (you may need to scrape abit of paint off the surface to acquire agood connection).

2 Any continuity reading indicates a shortcircuit to ground; replace the isolatorimmediately.

3 A large variation in the comparative read-ings on the capacitor charge would alsoindicate replacement, but I have neverseen this happen.

Due to the inherent voltage drop that occursacross a diode—typically 0.6 V to 0.7 V—

Testing the continuity in the opposite direction. First “flash” the capacitor byshorting it from one side to the other with a jumper lead, and reverse theDVOM leads. Again the meter reading will rise gradually as the capacitorcharges. Once the meter reading stabilizes, compare it to the first reading.

Testing for a diode short circuit to ground. Connect onemeter lead to either of the green wire terminals enteringthe device and the other meter lead to the case of the iso-lator. Continuity indicates a short circuit, and the isolatormust be replaced.

2

3

Battery-potential stray current is anothermatter, and it can cause profound metal corro-sion in as little as 24 hours! If rapid corrosionis noted and confirmed, it’s important to takequick action to prevent further damage tothrough-hulls and other bonded underwatermetals. This procedure is best done with ahelper, as jumping in and out of the bilge canget a bit tiresome.

Identifying Leakage Currentwith a DC Amp Clamp

To detect the low-level leakage resulting frombonding and grounding systems, you need ahigh-resolution DC amp clamp, such as theExtech 380942. If you can’t measure down to0.1 mA AC and 1.0 mA DC, you may not beable to detect leakage current that is strongenough to cause profound corrosion and, asdiscussed earlier, be potentially lethal to swim-mers around the boat.

If you suspect that DC stray current maybe causing problems on board your boat, findthe source using process of elimination (seeillustration page 118):

1 Start the test with the engine off.

2 Attach the amp clamp around the bond-ing conductor.

3 Activate the circuits on the DC panel-board one at a time.

4 If you suddenly get a reading on the ampclamp, you have identified the problemcircuit.


The high-resolution Extech 380942 amp clamp can mea-sure down to 0.1 mA AC and 1.0 mA DC.

Model 380942, Extech Instruments, www.extech.comModel 100-LCD-200-3/4'' Sea Clip, Swain Meter Company, www.swainmeter.com

HIGH-RESOLUTION DC AMP CLAMPS

5 Use a TDR to pinpoint the location of theleak (Chapter 3). The TDR is the besttool to find the location of a short circuitto ground within a circuit.

6 Repeat the test with the engine runningto check a faulty alternator or startermotor.

Identifying Leakage Currentwith a DVOM

It is also important to check the bonding sys-tem for current flow at several locations. It ispossible for leakage current from different loca-tions, such as bilge pumps and float switches,to “dump” itself out through the bottom of the

7 Replace the component immediately as itwill cause rapid corrosion of metal partssharing the same bilge water.

8 Another possible source of the voltagereading could be a stray, unterminatedconductor lying in the bilge or a con-nected conductor with bad insulation.

This chapter has touched on some of theclassic and routine tests you or a marine elec-trician can use to confirm that your boat’selectrical system, which is tied into thecathodic protection system, is in good order.These relatively straightforward tests will alsohelp you determine if you need to call in a cer-tified corrosion specialist.


A typical bonding system, showing locations to test with the amp clamp while activating DC circuits, to see if any stray cur-rent exists. (Reprinted with permission from Boatowner’s Mechanical and Electrical Manual, third edition, by Nigel Calder)

boat at only one through-hull point, bypassingthe others. Perform this test as follows:

1 Partially flood the bilge with salt water.

2 Set your DVOM to DC volts.

3 Attach the negative or “com” lead to theengine or battery ground (negativeterminal).

4 Activate the suspect bilge pump and usethe positive lead as a probe.

5 Tracking through the bilge water, slowlyhome in on the float switch or pump, asshown in the illustrations opposite.

6 If you start to get a voltage reading on themeter, you’ve found a leaking component.

Use a standard DVOM to track DC stray current through bilge water and home in on electrically “leaky” devices likepumps and float switches, and to find active DC positive conductors lying in bilge water. (Reprinted with permission fromBoatowner’s Mechanical and Electrical Manual, third edition, by Nigel Calder)

from battery

water penetrates switch seal

waterin bilge

current is fedfrom the positiveterminal on theswitch to the

other terminalthrough the

water

A leaking seal on a float switch will

result in stray-current corrosion

at the positive switch terminal. This will eat the

positive cable off the terminal, disabling the

switch and pump.


C H A P T E R

12Grounding Systems

Let’s delve a little deeper into the vital but often ignored subject of grounding sys-tems. Depending upon a boat’s equipment list, a grounding system will serve asmany as four primary needs:

1 Protect individuals from electrical shock (see Chapter 10).

2 Minimize corrosion (see Chapter 11).

3 Provide lightning protection.

4 Minimize RFI and/or provide a radio antenna counterpoise.

In this chapter we’ll look at lightning protection and the basic radio frequency groundplate. In Chapter 16 we’ll look at what happens when we tie in an SSB radio counterpoise,which is basically a slightly more elaborate grounding system that serves as half of theradio’s antenna system.

LIGHTNING PROTECTION

Lightning is both powerful and mysterious. We have been observing it for centuries, devot-ing much study and research to learning what it is, how to control it, and how to minimizeits powerful effects. That said, and in spite of all our efforts, the best lightning protection sys-tem (LPS) really can’t guarantee personal safety or protection from equipment damage. I tellmy seminar attendees that lightning is truly an act of God, and you can only do so much toinsure yourself against a strike; after that, you can just hope—or pray—for the best!

Most of what we know about lightning protection has been figured out by carefullyobserving the damage after a strike and drawing conclusions from these observations. Thestuff is just too hard to catch and experiment with!

So what have we learned from these observations as they relate to boat installations? Itcan be narrowed down to a few key points, which are compiled in ABYC Technical Infor-mation Report TE-4 (formerly Standard E-4), Lightning Protection. Below I’ve adaptedsome of the basic guidelines provided in that report for installing an LPS or modifying anexisting grounding system:

• Lightning is an electrical discharge, and moves due to a difference in electrical poten-tial. Like all electricity, it’s trying to get to Mother Earth, or ground.

• Once “captured” by an electrical conductor, the conductor should provide as straightand direct a route as possible to ground, and have the ability to handle the high volt-age and current present.


1 2 1

• The exposed conductor ground plate, orthe cumulative total area of multiplethrough-hull fittings and other exposedunderwater metal objects tied into thegrounding system, needs to be of suffi-cient size to ensure a low-resistance elec-trical connection to earth ground. TheABYC recommends at least 1 square footof surface area in salt water, which willgenerally work for everything but SSB.SSB manufacturers generally recommendat least 1 square meter or yard of exposedsurface area. Since fresh water is less elec-trically conductive than salt water, severalsquare feet of surface area should be usedfor lightning protection.

• To reduce the risk of the lightning “sideflashing” as it seeks a path to ground,heavy metal objects in proximity to alightning conductor should be electricallybonded to the lightning conductor. Also,lightning tends to jump out of “corners”created in the lightning ground wiringsystem, so minimize sharp bends.

The Elements of a LightningProtection System

The basic elements of an LPS are shown in theillustration. The primary conductor (alsocalled a down conductor) from the mastheadmust have the equivalent conductivity of apiece of 4 AWG (21 mm2) wire. You canachieve this by using an aluminum spar as theconductor. Carbon fiber spars are considerednonconductive for this purpose, so 4 AWGwire needs to be added. At the upper end, theconductor must terminate at what the ABYCtechnical report calls an air terminal—in otherwords, a lightning rod. The air terminalshould be the highest point on the mast by atleast 6 inches (150 mm).

The down conductor must be tied directlyto a grounding plate (or its equivalent) of at

grounding systems

least 1 square foot in surface area. You canachieve equivalency in exposed surface area bytying in other underwater metal objects suchas rudders, metal keel ballasts, through-hullfittings, and the like to the system, but youshould never connect the down conductordirectly to a through-hull fitting. If you do,and lightning strikes your boat, the strike mayblow the fitting out through the bottom of theboat. A tinned copper distribution bus barmakes a good link for the system if multipleunderwater metal objects are connected

Air terminal

Parallel pathParallel path

Bondingconductors(6 AWG)

EngineMetal tank

Immersedground plateor strip (1 sq. ft.)

4 AWG conductorshort as possible with8" min. radius bends

Primarylightningconductor(4 AWG)

Secondarylightningconductor(6 AWG)

The essential elements of a lightning protection system. (Reprinted withpermission from Boatowner’s Illustrated Electrical Handbook, secondedition, by Charlie Wing)


together via the grounding circuit inside theboat, or make up the entire grounding systemconnection to the seawater.

All of the tie-ins must use—as a minimum—6 AWG (13 mm2) cabling. This in itself createsa problem on some boats that already have abonding system in place, because the standardsfor that system dictate the use of either copperstrapping or minimum 8 AWG (8 mm2) wire.Consequently, if you choose to install an LPS,you would have to upgrade the bonding systemwiring. Many people find this to be a toughdecision, as it is almost impossible to performany kind of reliable cost/benefit analysis forinstalling the system. My view is that if you aregoing to spend any time offshore, or live in anarea of the world that is statistically prone tolightning activity, the scale gets tipped in favorof installing an LPS.

Although more exposed metal surface areais always better, the electrical conductivity ofthe various underwater metal componentsmight be a concern in some cases. Lead, forexample, is roughly a tenth as conductive ascopper, so even a good-sized lead ballast keelmay not provide sufficient conductivity. Iron,in contrast, is approximately a fifth as conduc-tive as copper, and even bronze alloys thatcontain copper are only about a third as con-ductive as pure annealed or hard-drawn copper.The best ground plate for an LPS is clearly apure copper plate. But even with a copperground plate in place, it can be worthwhile toincrease the total exposed surface area by con-necting all available through-hulls (typically ofa bronze alloy), stainless rudders, and evenlead keel ballasts.

Most of these metal components installedon or through the hull often have a coat ofantifouling paint on them. In theory, thisinsulates the metals from the seawater, but inpractice it’s not enough to make much of a dif-ference. When we consider the potentials

involved with lightning current, it’s going totake a better insulator than a coat of paint tohold it back!

Finally, tie in all large metal objects inproximity to any of the cabling included in theLPS, using 6 AWG cabling. (ABYC TE-4states that any large metal object within 6 feetof a conductor must be connected to the sys-tem.) On a typical recreational boat, thisalmost always means that all metal objectsmust be tied in, including fuel tanks, engines,and generators. The objective is to minimizethe risk of side flashing, in which lightningjumps out of the conductor to the metalobject in search of a better path to ground(even if there isn’t one).

Lightning Protection for ElectronicEquipment

What, if anything, does an LPS do to protectsensitive electronic equipment? This is a com-mon question among boatowners who arethinking about installing or upgrading anLPS. The simple answer is, nothing. The onlyway to really ensure that electronic equipmentremains unaffected by a lightning strike is tocompletely isolate it from the entire boat’selectrical system. Since this is generallyimpractical, it’s safe to say that you should sus-pect the integrity of all electronic equipmentafter a lightning strike, and carefully check allof its operational characteristics. It’s importantto note that LPS standards focus on personalsafety and protection of a vessel’s hull belowthe waterline, nothing more.

GROUNDING TO MINIMIZERFI EFFECTS

Electrical noise, which is essentially synony-mous with RFI, is interesting stuff in that itcan be transferred (radiated) through the air orthrough the wiring on board a boat. As discussed

in Chapter 9, one way to minimize its effectsis to create appropriate zones of separationbetween RFI sources and equipment that maybe sensitive to its effects. In the discussion inChapter 9, however, we were focusing on radi-ated noise. In this section, we will discuss howto minimize the effects of noise transmittedthrough the wiring on the boat via propergrounding techniques.

Inductance is a property of a conductor orcoil that determines how much voltage will beinduced in it by a change in current. Capaci-tance, which is the ratio of the electric chargetransferred from one to the other of a pair ofconductors to the resulting potential differ-ence between them, exists between any twoconductors insulated from each other. Inmany cases, the two conductors may be carry-ing equal but opposite electrical charges. Thedifference between them can be described as adifference in potential, which, as discussedearlier, is synonymous with voltage.

Any wire or conductor that has electricalcurrent flowing through it will have a magneticfield around it, and cabling that runs throughwire chases and conduits is a prime source ofRFI problems. Depending upon its frequency,RFI traveling down a given conductor may,quite easily, be able to couple with a parallel runconductor both inductively and capacitively.

Both inductance and capacitance can causea number of electrical problems on board amodern boat, including faulty readings on elec-tronic engine instrumentation and even thefailure of an electronically controlled engine.The best way to deal with this issue is to estab-lish a separation distance between the conduc-tors feeding these devices, but proper groundingcan also help.

Electrically shielded conductors are com-mon on some systems, such as network wiring,and the shielding will often take care of theproblem, but not always. Another approach is

the use of “twisted pair” wiring, in which twoor more conductors are twisted together fortheir entire length. Both techniques are widelyused by electronics vendors and on systemssuch as Mercury Marine’s SmartCraft networkand Teleflex’s i6000 control system. This is yetanother example of the blurring of the linebetween the electrical and electronics sides ofthe boat.

Noise generated by AC devices can be bro-ken down into two categories: differentialmode and common mode. Differential modenoise resides in hot (or ungrounded) and neu-tral (grounded) conductors, both of whichcarry current. Common mode noise, on theother hand, describes noise that exists betweeneither the hot and the grounding conductorsor the neutral and grounding conductors. Ineither case, the noise can easily manifest itselfas a hum emitted by audio equipment or asflickering or diagonal lines on a televisionscreen. Equipment vendors use filtering sys-tems to help control this, with some approachesbeing more effective than others. One of theways to further minimize the noise is the useof proper grounding techniques, such as spe-cialized capacitor-based circuitry. The opera-tive word here is “proper.” It’s possible, if doneincorrectly, to make matters worse.

Ground Loops and the Antenna Effect

A ground loop is a situation where there ismore than one ground connection betweentwo (or more) pieces of equipment. Theseduplicate ground paths create a loop antennathat will pick up interference currents. Theinherent resistance in the cable leads trans-forms the current into voltage fluctuations.Subtle induced voltages migrate through theground loop system, making the electricalpotential within unstable and allowing desir-able signals and noise to ride together. If thedesired signal is from an audio system, the

1 2 3grounding systems

result is audible noise, or static. In video orsatellite TV systems, the audio may be affectedand screen “static” may also occur. In com-puter or navigation equipment, the noise maycause operational problems with the gear.

The NMEA’s installation standard recom-mends connecting a networking cable shieldonly at one end of the shield. The standardcalls for the shield to be connected at thetalker end of networked devices (i.e., the data

delivery side, as opposed to the listener end,which might simply be a display screen.)

COMPARING ABYC ANDNMEA GROUNDINGSTANDARDS

In the field, no troubleshooter is in a positionto determine how equipment is designedinternally, at least as far as its grounding system


AC plug

signal ground earth ground equipment chassis ground

AC plug

device 1 device 2

earth grounds linked

device 1 device 2

still linked here through common AC ground (earth)

linked through cable shield

loop broken here—cable sheath not linked @ both ends

Single-Point Ground System

Continuous Loop

This typical equipment installation (top) has an unintentional ground loop that will very likely pick up interference. Theground loop above can be easily eliminated with the simple reconfiguration shown (bottom) and still be in compliancewith NMEA recommendations.

is concerned, or how much inherent noise thedevice may be generating due to design fac-tors. Therefore, it’s best to follow acceptedindustry standards and specific manufacturerrecommendations for electronics installations.

ABYC Standard E-11, AC & DC ElectricalSystems on Boats, addresses grounding issues, asdoes NMEA’s equipment installation standard.From the ABYC’s perspective, case grounding ofequipment is one of the most important consid-erations for a trouble-free installation. Anotheris the single-point connection between the DCand AC grounding systems on the boat. TheABYC standards for grounding are summa-rized in the illustration on page 126, whichI frequently rely upon for training purposes.

Keep in mind that this diagram reflectsgrounding needs as they apply to lightning pro-tection, shock hazard protection, and corrosionprotection more than to radio/electronic equip-ment needs and the elimination of electroni-cally induced “noise” (although a radio groundplate is shown). Compare it closely to theillustration on page 127 from ABYC StandardA-31, Battery Chargers and Inverters, andnotice what is in effect a ground loop betweenthe AC and DC sides of the battery charger.

The grounding wire on the DC side of thebattery charger circuit may seem redundant,but in the event of a case short with the DCpositive conductor, it is vital for providing aconductor capable of carrying high currentback to the power source to ensure that thefuse or circuit breaker in the DC positive linewill trip. In many cases, without this compara-tively large conductor, the current would tendto flow down the AC grounding conductor. Inall probability, this small conductor will nothave sufficient amperage-handling capabilities,so it will overheat and possibly cause a fire.

The reason the ABYC standards don’t gettoo concerned over this loop is based on thepremise that the DC grounding conductor is

not normally carrying any current; it’s merelyin place in case the worst happens. This raisesan important point about ground loops, how-ever: they are never a problem unless electricalcurrent is flowing through them. But from thetroubleshooter’s point of view, that is the prob-lem, because the current needed to make elec-tronic noise can be minute—too small topose a safety problem, but large enough toaffect the performance of some electronicequipment.

The NMEA standards are a bit stricter insome cases, and less strict in others. For exam-ple, ABYC E-11 states that grounding con-ductors can be no smaller than one wire gaugesize smaller than the DC power feed conduc-tor to the device in question, and in no casesmaller than 16 AWG (1 mm2) in size. WithAC equipment, the conductors are typicallythe same size, as the power feeds to AC devicesare virtually always installed with triplex cablewith equally sized conductors sheathed in theouter jacket. In contrast, NMEA recommendsusing no smaller than 12 AWG (3 mm2) inany case for grounding purposes and prefersthe use of 8 AWG (8 mm2).

The intent of the NMEA grounding stan-dard is also telling, and reinforces the differ-ence between ABYC and NMEA interests. Toquote from the NMEA standard: “This sec-tion details the recommended standards andpractices for installation of grounding systemsintended to support electronic equipment onvessels.” The NMEA is particularly focused onthe proper operation of electronic equipmentin a general sense. The ABYC, in contrast, isonly interested in the proper operation ofequipment if its faulty operation could cause asafety hazard to people on board the boat. It’salso important to keep in mind the note thatfollows the above statement from the NMEAstandard: “These are general recommendations.Specific and more stringent requirements may



+ –

Windlass

+– Wiper

Overcurrentprotection

Blower

Bilge pump

Float switch

Float switch

Grounding conductorGrounding conductor

Groundedconductors

Engine Engine

Batteryswitch

DC mainnegative

bus

Accessorynegative

bus

DC negative bus

Parallel switchor solenoid

AC grounding bus

Batteryswitch

+–

Fuel tankFill Gauge

Electronicsground plate

Immersed lightning ground plate or strip

Lightning down conductor(from lightning mast)

Large metal objects

Chainplates

Enginenegativeterminals

Seawater strainer

Seacock

++

–

+

–

–

Fuel tank

Housebattery

Startbattery

Startbattery

Horn

Sacrificial zinc

Grounding bus Bondingconductors

Grounding ANDbonding conductor

FillGauge

Distribution Panel

Main feedOvercurrentprotection

+–

+–

FORCORROSIONPROTECTION FOR

LIGHTNINGPROTECTION

FORSYSTEM

GROUNDING

A typical DC negative system and DC grounding system, adapted from ABYC Standard E-11, Figure 18. (Reprinted withpermission from Boatowner’s Illustrated Electrical Handbook, second edition, by Charlie Wing)

be specified by the specific manufacturer of anelectronic device.” So, what are the NMEA’sgeneral recommendations? I’ve adapted themas follows:

• All metal-cased electronics equipmentshall have a case ground tied to the boat’sDC grounding system with at least 12AWG cable, but preferably 8 AWG.

• All metal structures mounted to the ves-sel, such as tuna towers, radar arches, andoutriggers, are required to be connectedto the boat’s DC grounding systems by atleast two conductors with a minimum

size of 6 AWG. Further, these groundinglinks are required to be labeled “GroundConnection, Do Not Disconnect.”

• Finally, the NMEA standard describes RFgrounding quite specifically as a commonground used to reduce stray radio fre-quency noise and “set” all cases of elec-tronic equipment at ground potential,free from noise sources that may be intro-duced from being connected to the DCor AC ground buses.

This last statement is where things may geta bit confusing. The standard goes on: “The


Battery Charger Installation

power inlet (electricallyinsulated from the boatif isolator is installed)

shoreconnection

shore-powercable

main shore-powerdisconnect

circuit breakerbatterycharger

DC groundingconductor

AC groundingconductor

main ACgrounding bustwo-pole, three-wire

grounding-typeplugs and receptacles

optionalgalvanicisolator

polarityindicator

engine negativeterminal or its bus

battery batteryswitch

to enginecranking

motor

shor

e si

debo

at s

ide

shore-power cable connector

ungr

ound

ed c

ondu

ctor

(bl

ack)

grou

nded

neu

tral

con

duct

or (

whi

te)

grou

ndin

g co

nduc

tor

(gre

en)

L

N

Notice the differences between the ABYC standards for grounding in a battery charger installation per ABYC StandardA-31 (shown here), and the more general installation standards for lightning, shock, and corrosion protection as statedin Standard E-11 and shown in the previous illustration. If you study these diagrams carefully, you’ll notice that in the Stan-dard E-11 drawing, each component connected to the grounding system has only one wire linking it to ground. Noloops are shown. But in the case of the Standard A-31 drawing, a loop is created between the AC and DC sides of thegrounding system (highlighted area). (Reprinted with permission from Boatowner’s Mechanical and Electrical Manual,third edition, by Nigel Calder)

RF ground bus shall be connected to the DCground, and must be directly connected to theengine ground and through-hull ground platefor the specific purpose of reducing RF noiseon board.” Herein lies the confusion. What isbeing called for is a dedicated RF ground busthat may be tied into the rest of the boat’sgrounding buses (AC and DC) and also at the“engine negative terminal” as the ABYCdescribes it. So the question becomes, is it iso-lated from everything else or is it connected?

This is a case where a picture says a thou-sand words. Use the illustration on page 126as a guide for how these connections should bemade, and you will be compliant, not onlywith ABYC E-11, but also with the NMEAelectronics installation standard as it applies togrounding.

If your equipment is installed in accor-dance with the ABYC recommendations asshown in that illustration, and you still experi-ence noise-related issues, then the solution isan electronics grounding system that is com-pletely isolated from the rest of the onboardsystem. You will still be in compliance withthe ABYC standard, as long as the rest of thecomponents shown in the illustration arewired as shown.

That said, I’ve rarely seen a situation wherethe configuration in the illustration causedany problems with equipment operation. Inmy opinion, the difference between the NMEAstatements and the ABYC diagram is one ofsemantics rather than a clear-cut difference.The NMEA does, after all, reference ABYC E-11

as the guide for equipment wiring within itsinstallation standards.

TROUBLESHOOTING REDUX

Before we move on to Part 2, in which we’lllook at electronics installations, I’d like toreemphasize what I feel is crucial to effectiveelectrical systems troubleshooting.

It’s important to look at your work andyour routines carefully, think about what youdo most frequently, and about what you coulddo if you had access to a given piece of gear. Ifyou’re a professional marine technician, con-sider how it might help your bottom line; ifyou’re a boatowner, consider the money you’llspend and the time you’ll have to invest tolearn how to use a new device, and weighthose against the limited usage to which you,as the technician responsible for a single boat,will probably put it. Go through a cost/benefitanalysis to determine which devices make themost sense for you to purchase.

Whether you’re a professional or an ama-teur, don’t immediately run out and buy everyinstrument we’ve discussed in Part 1. By them-selves, they won’t automatically make you abetter electrician or a smarter boatowner. But ifyou follow some of my recommendations andsuggestions, and attain a clear understandingof the capabilities and the applications of eachnew instrument before you consider buyingthe next one, you will have mastered new, use-ful skills and elevated yourself to a higher levelof competency.


P A R T

MARINE ELECTRONICSINSTALLATION ANDTROUBLESHOOTING

T he foremost standards group in North America that deals with marineelectronics installations is the National Marine Electronics Association(NMEA), which developed its standards, in part, as a response to the

cries for help coming from its members—electronics equipment vendors.Why the distress? Many of the performance issues related to electronics equip-ment aboard boats were the result of shoddy or incorrect installation practices.

My contribution to the dialogue is Part 2 of this book. Here’s a briefoverview:

• Chapter 13—general issues related to equipment installation.

• Chapter 14—installation and troubleshooting of communications systems(VHF, SSB, and satellite), position-finding systems (GPS), and radar.

• Chapter 15—installation and troubleshooting of supplementaryequipment, such as depth sounders, wind instruments, and autopilots.

• Chapter 16—coaxial cables and antennas.

• Chapter 17—onboard networks.

2


C H A P T E R

1 3

c

Electronic EquipmentInstallation Guidelines

My goal in this chapter is to provide an overview of the issues addressed in theNMEA installation standards as well as in the ABYC standards referenced bythe NMEA, and to discuss some general material that is not specifically

addressed by either organization, including some installation guidelines.From our point of view as equipment installers and installation troubleshooters, we’ll

encounter more commonalities than differences between the various makes and models ofequipment. For example, installing and troubleshooting a Northstar GPS isn’t much dif-ferent from installing and troubleshooting a Furuno GPS unit.

ERGONOMICS

Although not specifically mentioned in the NMEA or ABYC standards, one of the issuesto be considered as part of any equipment installation is the human interface. In the caseof marine electronic equipment, such as radars, chartplotters, VHF radios, and fishfind-ers, the ability to see the display and work the controls easily, especially while the boat isunderway, is important. The general term I’ll use to describe all of this is ergonomics.

Ergonomics is defined in my Funk & Wagnall’s dictionary as “the study of the relation-ship between man and his working environment, with special reference to anatomical,physiological, and psychological factors; human engineering.” So, when considering theinstallation location for electronic equipment on board a boat, you have to be part techni-cian, part physiologist, and part psychologist to get the job done right.

This multi-view perspective is important because much of the equipment we’ll be cov-ering in the following chapters provides essential input to the boat operator. He or shemust be able to easily acquire this data, sort it out mentally, absorb it, and analyze it in atimely manner (this is especially true in high-stress situations such as bad weather). It isnot my intent to overstate the importance of this subject, but over the years I’ve seen toomuch equipment installed that was seriously handicapped in its basic functions becausethe installer didn’t think about the operator’s needs when underway. And that is the keypoint: Installers should position equipment so that it is usable while the boat is underway.

So let’s put on our physiologist’s hat for a minute and see what we need to consider.First, think of the senses we use when operating electronic equipment—sight, hearing,and touch—and ask yourself some basic questions:


electronic equipment installation guidelines 1 3 1

• Can the operator easily see the equipmentand its screen or display?

• Can the display be read in bright sun-light?

• Can the display be read when the opera-tor wears polarized sunglasses?

• Is the display so bright that it disturbs theoperator’s night vision?

• Is the display mounted in such a waythat it reflects off the wheelhouse windowand obscures the view ahead?

Viewing angle is an important considera-tion for many of these questions, as is the avail-ability of display settings for adjusting bright-ness and/or selecting “night viewing.” Whiledisplay settings are a function of the equip-ment, they’re also an important component ofthe overall ergonomic situation. A display thatcan’t be read in the prevailing situation is just asworthless as one that doesn’t work.

Similarly, consider hearing and touch. Let’suse a VHF radio installation as an example. Isit mounted where the operator can hearincoming transmissions over the sound of theengine? Can the controls be easily reached andaccurately adjusted while the boat is under-way, even in rough seas? These and similar fac-tors will contribute to or detract from theeffectiveness of a given installation.

Electronics installations in open cockpits,such as in most sailboats, can be particularlychallenging because direct sunlight can washout display screens. In some cases, sunlightcan make equipment overheat, causing displayscreens to shut down. While screen technol-ogy has come a long way in the last ten years,and the term “daylight viewable” is now acommon marketing term used by manyequipment vendors, the bottom line is thatsome equipment is just better suited to a par-ticular location. If you have to leave the helm

VHFcompass

Center consoles present an installation challenge as there’s not a lot of room for whatis often a lot of desirable electronics. Given those limitations, this installation is quitegood from an ergonomic point of view. Assuming that the helmsman will be standingmost of the time, most of the controls are quite visible and accessible. There is, how-ever, the potential for magnetic interference between the VHF radio and the steeringcompass, so this may not be the best location for the VHF radio.

1 3 2 marine electronics installation and troubleshooting

Both ergonomics and the potential for magnetic interference have been dealt with rather effectivelyhere. LCD screen displays, as in the chartplotter located to port, have very low magnetic emissionsand, although mounted close to the compass, should have no effect. The T-top on this center con-sole boat will provide shade that will help improve screen visibility even on very sunny days.

engine monitors(dual outboards)

VHFchartplotter/radar display

electroniccompass

autopilotcontrol

A typical sailboat binnacle-mount system. These work best under a bimini top to ensure screen visibility.Without a bimini, the installer would have to consider the “day bright” capabilities of the equipment.

multi-data display

chartplotter

compass

wind angle indicator autopilot control

depth sounder

and run down to a navigation station to checkyour position, that’s bad ergonomics—andpossibly bad seamanship.

WATERTIGHT INTEGRITY

Is the equipment waterproof or water resistant?The levels of watertight integrity of equip-ment are often hidden in obscure specificationsthat are typically incomprehensible withoutreference to the standards. And there are severalstandards that apply to water-resistant enclo-sures for electronic equipment.

In the Code of Federal Regulations (CFR)Title 46, Part 110, the U.S. Coast Guarddefines waterproof as: “Waterproof meanswatertight; except that, moisture within orleakage into the enclosure is allowed if it doesnot interfere with the operation of the equip-ment enclosed. In the case of a generator ormotor enclosure, waterproof means watertight;except that, leakage around the shaft mayoccur if the leakage is prevented from enteringthe oil reservoir and the enclosure provides forautomatic drainage.” The original text of thisregulation included the following definition:“Waterproof machine means a totally enclosedmachine so constructed that a stream of waterfrom a hose with a nozzle 1 inch in diameterthat delivers at least 65 gallons per minute canbe played on the machine from any directionfrom a distance of about 10 feet for a period ofnot less than 5 minutes without leakage.”

Another standard, which comes from a res-olution made by the International MaritimeOrganization (IMO), applies to handheld VHFradios used in life rafts. The revised “recom-mendation on performance standards for sur-vival craft portable two-way VHF radio tele-phone apparatus” describes several performanceissues related to waterproof integrity: “Theequipment should: be watertight to a depth of1 m for at least 5 minutes, maintain water tight-ness when subjected to a thermal shock of 45°C


under conditions of immersion, and not beunduly affected by seawater, or oil, or both.”

Perhaps the most recognized and widelyused rating system is known as the IP (ingressprotection) rating, which is the work of theInternational Electrotechnical Commission(IEC). It includes a foreign-object rating aswell as a waterproof rating, which runs from 1to 8, as shown in Table 13-1 on page 134.

An example of how this rating would look is“IP X7.” Using Table 13-1, we can decode thisrating as follows: X indicates no rating for for-eign objects, and 7 indicates protection againstthe effects of immersion to 1 meter in depth forup to 30 minutes. As another example, IP 67indicates a piece of equipment is dust tight (6)and protected against immersion (7).

One other rating system you are likely toencounter is the Japanese Industrial Standard(JIS). This standard is nearly identical to the IPstandard. Like the IP system, the waterproofgrade may range from 1 to 8. The higher thenumber, the better the protection; for example,a product that is waterproof rated to JIS 6 hasbeen subjected to a test that includes exposure topowerful water jets from all directions with noill effects. A JIS 7 rated product has been testedto withstand being dropped in the water (up to1 meter deep) and retrieved fairly quickly. Thisis a useful rating for handheld VHF radios.

Check the product specification sheet forany or all of these ratings. They can help youdetermine the appropriate location for a pieceof equipment—in an open cockpit versusinside a cabin or other enclosed space on aboat. It’s valuable information that can dra-matically affect the usable life of the electricalor electronic gear used on boats.

THERMAL LIMITS

In Chapter 5, we discussed the use of aninfrared heat-sensing gun to check ambientand equipment temperatures for problems or

potential problems. Here we’ll go over boththe NMEA and ABYC standards related totemperature control.

The NMEA standard refers to “equipmentthat requires air circulation for cooling,”which I consider to be any piece of gear that isequipped with a built-in cooling fan, mountedon a heat sink, or has finned radiating plates aspart of its enclosure. The NMEA standardstates that “sufficient means shall be providedto supply circulation of air behind the equip-ment displays.” And for devices that use cool-ing fans, it states “there shall be sufficient aircirculation to cool the equipment duringdirect sunlight operation with ambient tem-peratures of 100°F.”

The ABYC is quite specific about temper-ature parameters in two of its standards. Stan-dard A-31 requires that battery chargers andinverters be designed to operate at an ambienttemperature of 122° (50°C) and be able towithstand an ambient temperature of 158°F(70°C). ABYC A-28 requires galvanic isola-tors that will be installed in machinery spacesbe rated to 122°F, while those that will not beused in machinery spaces be rated to 86°F(30°C).

In addition, manufacturers establish theirown installation guidelines regarding temper-ature. ICOM, for example, states in the docu-mentation for one of its SSB transceivers thatit should not be mounted in locations subject


Protection Against Protection Against1st Digit Foreign Objects 2nd Digit Moisture

0 Not protected 0 Not protected1 Protected against objects 1 Protected against dripping water

greater than 50 mm2 Protected against objects 2 Protected against dripping water

greater than 12 mm when tilted up to 15°3 Protected against objects 3 Protected against spraying water

greater than 2.5 mm4 Protected against objects 4 Protected against splashing water

greater than 1.0 mm5 Dust protected 5 Protected against water jets6 Dust tight 6 Protected against heavy seas

—— 7 Protection against the effects of temporary immersion up to 1 m

—— 8 Protection against prolonged submersion beyond 1 m

Note: The letter X is used to designate no rating in either category.Source: Underwriters Laboratories

Environmental Ratings for Enclosures Based on Ingress Protection (IP)Code Designations

TABLE

13-1


The back of this heavy-duty DC-to-AC inverter has air-circulation ports for a built-in cooling fan. If you mount this inverterin an area with high ambient temperatures (as in an engine room), and the fan has only hot air to circulate, cooling effi-ciency will be reduced, and eventually the inverter will stop working.

The heat sink fins on this diode-type battery isolator musthave cool air circulating around them or the diodes willalmost surely overheat and fail.

to temperatures below –4°F (–20°C) or above140°F (60°C).

The bottom line regarding temperature issimple: There may be specific industry stan-dards that dictate how you as a technician orboatowner should proceed, and there may bemanufacturer recommendations that apply. Inall cases, you should follow the manufacturer’sspecific recommendations. In the absence ofthose, look to the industry standards for guid-ance. You must find the applicable limits andconsider how they can be met on your boat oryour customer’s boat. Sometimes this is as easyas finding a new location for the device inquestion. Other times, it may require the addi-tion of a cooling fan to facilitate proper air cir-culation or the installation of louvered vents toventilate otherwise dead-air spaces on board(see photo page 136).

diodes (embedded in epoxy“potting” material, which

helps transfer heat tothe cooling fins)

heat sink fins

POWER SUPPLY

The scene is classic. The boatowner boards hisboat and fires up the radar, color chartplotter,fishfinder, VHF, and whatever other electron-ics are on board, reveling in the glory of all ofthat expensive techno-wizardry. Life is good.Then he starts the engines . . . only to see allthe electronic equipment blink out.

What’s happened here is simple: enginecranking draws a lot of amperage, and in thiscase it pulled the system voltage below the min-imum operating parameters set by the electronicequipment vendors. Fortunately, no permanentharm has been done. Once the engines are run-ning (and assuming the engine alternators arefunctioning normally), voltage will stabilize, and

the equipment will come back online and func-tion normally. But that momentary loss ofpower can cause any microprocessor-controlledmemory function within a given device to“dump” the memory, which is a major hassle ifthe unit in question has a lot of data entered.This scenario is not only inconvenient, it’s alsoone of the most common electrical/electronicproblems experienced on boats, and it drivessome owners crazy.

You can adopt one of three strategies toaddress this problem:

1 The NMEA recommends installing a sep-arate, isolated battery bank to supply allthe electronic equipment. This bank canbe fed by the engine’s alternator for


You can use a miniature “pot fan” to supply forced-air circulation behind enclosed electronicspanelboard arrangements. Coupled with some additional louvers to let fresh air into thespace, small fans can help tip the temperature scale in the right direction. A word of caution,though; these fans are not typically rated for ignition protection, and therefore they should notbe used in places such as battery boxes or gasoline engine rooms where ignition protection ismandatory.

recharging, but does not add to the enginestarting circuitry.

2 The more common strategy is to have allthe batteries supplying all the boat’s DCloads, including the electronics packageand the engine starter circuit. However,this setup requires that all cable runs besized to maintain an absolute minimumvoltage drop, and that the battery bankhave sufficient capacity to crank theengines while maintaining a crankingvoltage of greater than 10.5 V.

3 The third option is to install a DC-powered UPS device for the electronicsmain power supply, such as theStartGuard DC power conditioner fromNewmar. These boxes, which sell forabout $200, are similar in purpose to

the UPS devices common in computerinstallations; they contain a small bat-tery that “kicks in” to maintain stablevoltage output when there is a drop ininput voltage. The primary difference isthe power source, which is DC, versusthe AC used by land-based computers.The StartGuard UPS has a maximumoutput of 20 amps. If you need addi-tional current capacity, you can installmultiple units.

I recommend either option 1 or option 3.If you are interested in option 1—an isolatedand dedicated battery supply for poweringelectronic equipment—keep in mind thatspace limitations and added cost may rule itout on your boat. In that case, try option 3, aDC-powered UPS device.


Typical integration of a DC-powered UPS device with onboard electronics.

UPS

INPUT STARTER OUTPUT12 VOLT

GPS receiver

loads (20 amps max)+ 12V

– 12V

** 2 amp fuse

** 2 amp fuse

to 12 V battery to starter #1

key starter

+12 V

+ 12 V fromfused source

(–) common(wiring option)

OR

push-buttonstarter switch

to starter #2switch or solenoid

+

–

+

–

*

*

* Refer to manufacturer’s instructionsregarding overcurrent protection.

† Terminal block not provided. Multiple wires may be attached directly to UPS if preferred.

†

** Recommended; must be supplied by installer.

VHF radio

starter solenoid

GUIDELINES SUMMARY

Before we move on to more specific installa-tion concerns in the following chapters, here’sa summary of some general electronic equip-ment installation guidelines:

• Be sure voltage and amperage can bedelivered to the equipment in the neededamounts under all conditions, includingduring engine cranking and activation ofhigh-demand loads like electric winches,anchor windlasses, and bow thrusters.Achieving this may require the installa-tion of a UPS device for the system orextra batteries.

• Voltage parameters of the gear in questionmust be confirmed by the installer ortroubleshooter. Some devices (such asradar) have broad acceptable ranges foroperating voltage, whereas others (likeSSBs and fishfinders) tend to have com-paratively narrow operating ranges.


• Reverse polarity can easily and instantlydamage electronics. Beware of reversingthe positive and negative feed wires.

• Consider possible spray conditions in theintended installation location, and ensurethe equipment matches the situation(check the equipment’s IP or JIS water-proof rating).

• Consider ergonomics when mountinggear: will it be visible, audible, and reach-able and convenient?

• Be concerned about both RFI and EMI,and provide appropriate levels of separa-tion and shielding for equipment andcable runs throughout the boat.

• Make sure that antennas and transducersare oriented correctly from a directionalperspective so that their beam transmis-sion is not obstructed by boat structures.

StartGuard NS-12-20, Newmar, www.newmarpower.comC-Power, Charles Industries, www.charlesindustries.com

DC-POWERED UPS DEVICES

C H A P T E R

14

bus bar

Installing Communicationsand Position-FindingSystems and Radar

Proper installation of communications equipment, position-finding GPS-based sys-tems, and radar is serious business. Boatowners rely on this gear to ensure theirsafety and, if necessary, call for help, perhaps in a life-threatening situation. Such

equipment is vital to the safe operation of a boat, in contrast to, for example, installing aCD player. Yes, a CD player is a piece of electronic equipment, but if the boatowner can’thear the latest Alan Jackson CD while underway, it’s not a crisis. So, please, as you readthrough the material that follows, approach your work as though you might be helping tosave someone’s life. Don’t cut corners.

COMMUNICATIONS SYSTEMS

Communications systems on boats used to entail perhaps just a VHF radio. But nowa-days most boaters consider SSBs, cell phones, satellite TV and/or Internet access basicrequirements. And of course, all this additional equipment means more work for marinetechnicians!

VHF Radio

VHF radio is the most common of all marine electronic equipment used for boat-to-boatand boat-to-land communication. It operates in the frequency range of 156 MHz to174 MHz. In recent years, features such as digital selective calling (DSC), global posi-tioning system (GPS), and the Global Maritime Distress and Safety System (GMDSS)have expanded the use and functionality of VHF radios by incorporating the ability totransmit time, position, and ownership information in the event of an emergency. Whileimproving safety at sea, these features have altered the VHF’s traditional installation pro-cedure, so we’ll review the installation process.

RangeIn the United States, the transmitting power for marine VHF is limited by the FCC to amaximum of 25 watts. Canadian regulations mirror the U.S. regulations in this area.(Land-based units can have much higher power under the regulations.) I have found that



estimating 1 statute mile per watt of transmit-ting power is a fairly reliable rule of thumb forthe expected range of a VHF radio. For example,a 5-watt handheld VHF would have a 5-milerange, and so forth.

With transmitting power limited by law,one of the only practical methods of increas-ing a VHF radio’s effective range is to locatethe antenna higher. Since VHF operates on aline-of-sight basis, raising the antenna extendsits range by extending the effective horizon(see Table 14-1).

We will look further at issues relating tothe antenna and the coaxial cable that con-nects it to the radio in Chapter 16.

WiringSince low voltage to the radio will dramaticallyaffect its performance, proper wiring using thecorrect gauge to ensure minimum voltagedrop, and high-quality termination points, arecritical to the installation.

Installation guidelines:

• Use the wire gauge as specified by themanufacturer for the DC power feed andnegative return.

• Install wiring to keep voltage drop tothe maximum of 3% based on ABYCstandards.

Transmitter Height (ft.)

Receiver Height (ft.) 5 10 20 40 60 80 100 200 4005 5 6 8 10 12 13 14 19 26

10 6 7 9 11 13 14 15 20 2720 8 9 10 13 14 16 17 22 2940 10 11 13 15 17 18 19 24 3160 12 13 14 17 18 20 21 26 3380 13 14 16 18 20 21 22 27 34

100 14 15 17 19 21 22 23 28 35

1. The distances in the table are based on the formulas D = 1.17 �H and D1 + D2 = 1.17(�H1 + �H2) whereD = distance in nautical miles, H1 = height in feet of the receiver, and H2 = height in feet of the transmitter.Reprinted with permission from Boatowner’s Illustrated Electrical Handbook, second edition, by CharlieWing

Line-of-Sight Distance, D1 + D2, for VHF Radios1TABLE

14-1

Line-of-sight transmit/receive distances for VHF radio. (Reprinted with permission from Boatowner’s IllustratedElectrical Handbook, second edition, by Charlie Wing)

D1 D2

H1 H2

• Follow Standard E-11 to determine theappropriate wire size to use. Rememberthat wire size is based on the length of thewire run from the power source to theVHF radio (see the ABYC voltage droptable, page 43).

DSC and GMDSSDSC is integrated into all new VHF radios andis a part of GMDSS. The interface between theVHF radio and GPS receiver allows positioninformation to be transmitted in the event of aDSC emergency call; all you have to do is pushthe emergency button now found on all newradio sets to transmit your boat’s exact positionand time data to the U.S. Coast Guard.


• Use an NMEA-approved cable attach-ment to link your VHF radio to the GPS

unit (see above illustration). (This inter-face may be part of your boat’s network;see Chapter 17 for more on networking.)

• Follow the manufacturer’s recommenda-tions for the exact terminal connections.

As the last step to a fully capable DSCinstallation, the boatowner must acquire aMaritime Mobile Service Identity (MMSI)number. Once entered, this nine-digit numberbecomes the permanent identifier for yourboat. When DSC is activated, the MMSI willprovide rescue personnel with pertinent boatand owner information along with time andposition data.

In the United States, you can get anMMSI from the FCC for a fee, or for free bycontacting BoatU.S. (www.boatus.com/mmsi)or Sea Tow (www.seasmartvhf.com). In Canada,all applications for MMSI numbers must be

DC panel

GPS receiver

DC –

DC +

VHFcoaxial cable

antenna

bus bar

in-line fuse

DC— fromelectronicequipment

bus bar

NMEAcable

1 4 1installing communications and position-finding systems

The wiring and cable connections to a VHF radio. Notice the interface with the GPS receiver via an NMEA cable link.

receiver. The procedure for entering the MMSIis radio specific—it is imperative you have theowner’s manual for your radio in hand.

Location, Location, LocationAs mentioned in the ergonomics discussion inChapter 13, the mounting location for theradio is a concern, not only from the point ofview of ergonomics, but also regarding EMI.A VHF has two built-in magnets, one for thecabinet speaker and one for the microphone.If the radio and compass are too closetogether, stray magnetism from the VHF willinterfere with the boat’s steering compass. TheNMEA recommends that the radio and itsmicrophone should be no closer than 3 feetfrom the compass or any onboard antenna.

Note: Always check for compass deviationwhen installing electronic equipment of anytype near a magnetic steering compass, regard-less of whether the equipment has built-inmagnets or not. Look for compass needlemovement as you place or activate electronicequipment nearby, and modify your place-ment as needed.

Single-Sideband Radio

Single-sideband (SSB) radio is the long-rangecounterpart to VHF radio. Where marineVHF is limited to line-of-sight communica-tions and a maximum of about 25 miles, SSBradio has the potential to transmit and receiveover hundreds or even thousands of miles. AnSSB radio bounces radio signals off the lowerlayers of the earth’s atmosphere, which in turnreflect the signals back to earth. (You canthink of SSB transmissions as giant trianglesspanning many miles.)

Voltage and Current RequirementsAn SSB’s appetite for amps covers a fairlybroad spectrum, ranging from about 2 to3 amps in Standby/Receive mode to about


DEVIATION THE HARD WAY

A few years ago, I learned my lesson about electronics-induced compass deviation the hard way——almost literally.My 25-foot walkaround has a very compact helm station,and all the electronic equipment——GPS chartplotter,fishfinder, water temperature gauge, and VHF radio——wastightly clustered at the helm. In the center of the cluster, andno more than 12 to 18 inches from any of them, was themagnetic steering compass.

When my VHF radio failed, I bought a new unit, completewith all the bells and whistles, and mounted it in the same loca-tion as the original unit. I tested it and it worked fine. Severalweeks later, I was fishing on Narragansett Bay when a thickfog rolled in. I decided to head for home, and checked thechartplotter for the magnetic heading I would need to get tothe breakwater at the entrance to my home port.

Off I went, paying more attention to the compass thanthe chartplotter and following the predetermined headingusing the steering compass. About the time I thought Ishould see the breakwater, it suddenly appeared about100 feet dead ahead—not the opening in the breakwater,where my heading should have positioned me, but thewall itself. Fortunately I was cruising slowly at 5 knots, andwas able to avoid disaster. But what had happened?

After replotting everything, I realized that I had a12-degree deviation in my compass. The cause was sim-ple to figure out. I’d never had a lick of deviation in thattrusty Ritchie compass until I installed the new VHF. Thespeaker magnets in the new radio were much more pow-erful than those in the old unit, and they had caused thisnew deviation.

I removed the radio and reinstalled it in a new loca-tion, away from my compass but still ergonomically placedfor ease of use. Another lesson learned, and almost thehard way——breakwater hard!

submitted to the Canadian government directlyvia Industry Canada. To learn more about theirprocess, go to http://strategis. ic.gc.ca/epic/internet/insmt-gst.nsf/en/ sf01032e.html.

Once you acquire an MMSI number, becareful to enter it correctly into the radio


30 amps when transmitting. This is not toomuch of a problem unless the operator isthe chatty type or spends a lot of timedownloading weather charts via a modem.However, 30 amps of consumption is aconsiderable amount, and it will drain bat-teries rather rapidly if they are not beingrecharged.


• Be sure to use correctly sized power feedwires to serve the unit, especially in con-sideration of restricting voltage drop to amaximum of 3%. Based on ABYC E-11,you will need a minimum of 6 AWG(13 mm2) wire to supply power to a 12 VSSB set over a 20-foot cable run.

• Adhere to voltage supply parameters. Mostif not all SSB units operate at a nominal12 V. For a boat with a 24 V or 32 V sys-tem, you will need a DC-to-DC powerconverter. Overvoltage supply to the trans-ceiver will damage the unit quicker thanyou can snap your fingers! A typical 12 V(nominal) SSB has a voltage operatingrange of 13.6 VDC, ±15% maximum.Consider this 15% an absolute maximumbecause performance will definitely beaffected if power falls below –15%.

• Use the 3% voltage drop parameter toensure peak performance. Lower-than-acceptable voltage will have a profoundimpact on power output from the unitand its potential range. It may be usefulto think of potential power out of theunit as proportional to the poweravailable to operate the unit.

• An SSB requires a first-class groundingsystem to function at its peak, and theantenna needs what is known as acounterpoise, a ground that is an integralpart of the antenna system (discussedfurther in Chapter 16).

• For best results, use the multicable har-ness provided by the SSB manufacturer(see next page), which typically includesthe coaxial antenna lead, power cables,and a cable to connect the automaticantenna tuner (a commonly specifiedavailable option). All the individual cablesin the harness are terminated with water-tight connectors for the tuner or trans-ceiver, and all the individual conductorswithin each cable are connected to theright pins. Stick with the original manufac-turer’s harness! This is not an area whereyou will win high marks for creativity.

Regulations for SSB use vary from onecountry to another. In the United States, FCCrules apply. Additionally, specific regulationsapply if the radio includes DSC and GMDSS.

This is where a true electronics equipmentspecialty house can put you on the right course.Electronics specialists are usually FCC licensedand will be well versed in the specific regula-tions as they apply not only to installation ofequipment, but also to licensing requirementsfor equipment operators. Inquire before you getin trouble, because the rules changed a fewyears ago. In some cases, an FCC license isrequired to perform installations.

Noise Issues with SSBElectrical “noise” on board can dramaticallyaffect an SSB’s ability to produce clear, static-free signals in Receive mode. Potential noiseemitters include anything that relies on anelectrical spark for its operation—virtually anymotor, fluorescent lights, and relays and sole-noids. After installation, test your SSB toensure that the antenna is not receiving anyemitted noise.

Since SSBs operate over a fairly broad fre-quency spectrum (from 2 MHz to 22 MHz),it is hard to predict which electrical devicesmight contribute to excessive background


noise. To help you find the culprit, conduct aprocess-of-elimination test, as follows:

1 Set the radio between channels at the lowend of the spectrum (towards the 2 MHzend).

2 Activate other AC and DC equipmentone at a time.

3 Run all the engines, including ACgenerators.

4 Repeat this test sequence at all of the com-monly used frequencies to be sure that youhaven’t missed an annoying RFI emitterrunning at a higher frequency.

Keep in mind that some background noiseis normal and unavoidable. But if, for exam-ple, audible noise dramatically increases whenyou turn on a fluorescent light, you’ve isolated aculprit. Also keep in mind that some electrical

equipment is cyclical and may only functionintermittently (such as bilge pumps). Checkcycling loads when they’re actually operating,not just with their power activated.

If you identify a noise source during thiselimination process, it’s best to consult theradio manufacturer or its local dealer to deter-mine the best type and rating of filter to install.

Your concerns, as the electrical installer, arelargely limited to those mentioned: the powersupply, cabling, noise, antenna, coaxial cable,and antenna counterpoise. Any problems notrelated to these issues must be addressed by anelectronics technician.

Satellite Communications Systems

Whether they’re used for global telephone con-nectivity, Internet access, or simply tuning intoa favorite television or satellite radio show,satellite communications (satcom) systems

battery

laptop

USB hubcommunication portPactor modem

to antenna

SSB transceiver

antennatuner

DC power supply

antenna counterpoise

A typical cabling configuration for an SSB radio. On a high-end boat today, you will probably see a Pactor modem connected asan auxiliary device for sending and receiving e-mail via radio. The boat’s laptop PC will also be linked to the SSB to provide a dis-play and input device for e-mail, weather charts, and the like. Specific wire terminal identification will vary from one system toanother, but this illustration shows a general layout. The connecting cables shown are all multicable harnesses with the exception ofthe antenna coaxial and the wired connection between the antenna tuner and the counterpoise.

have gone mainstream on recreational boatsover the last decade. The need (or perhaps per-ceived need) of boatowners to stay connectedin one way or another has driven this change.As a result, boatowners today have a variety ofchoices in satcom systems. The capabilities ofmost of the common two-way satcom systemsare shown in Table 14-2 on page 146.

Satcom InstallationMost of the usual installation considerationsapply to satellite systems:

• Maintain the usual 3% maximum voltagedrop to ensure peak performance, espe-cially since communications systems playsuch an important role in vessel safety.

• Use appropriately sized wire. Currentdraw is fairly low, ranging from about2.5 amps to about 5 amps, so wiring isnot as much of a concern as with, forexample, an SSB.

• Do not alter the length of the antennacable (as with almost all coaxial cableinstallations) or you may seriouslydegrade performance.

Satellite domes are showing up on a lot of boats lately, due to our desire to stay connected.

phone handset and cradle

single coax cable design

DOME ANTENNA

transceiver

fax

auxiliary phone

ground out

data

A typical satellite-based telephone/data system using the InmarsatMini-M satellite system.


14

6m

arin

e elect

ro

nic

s installat

ion

and

tr

ou

blesh

oo

tin

g

Inmarsat InmarsatFleet 55 Inmarsat Inmarsat Mini-C

Application and 77 Fleet 33 Mini-M Inmarsat-C (eTrac) Iridium Globalstar SkyMate

Voice yes yes yes no no yes yes noE-mail yes yes yes yes yes yes yes yesInternet and yes yes yes no no yes yes no

attachmentsFax machine yes yes yes no no no yes (with no

capable additional (outboundequipment) only)

Automatic no no no yes no no no noweather/safety

Receive weather yes (via yes (via yes (via text weather no yes (via yes (via yes (radarcharts Internet) Internet) Internet) Internet) Internet) plus selected

charts)GMDSS/Distress yes (77 only) no no yes no no no no

Common Satellite Communications SystemsTABLE

14-2

• Closely follow the equipment manufac-turer’s recommendations for antennaplacement and separation from othertypes of antennas mounted on the boat.

• When planning electronics installations,keep in mind possible interferencesources in either direction.

You can use the above list to confirm thatthe electronics specialist has installed yoursystem(s) correctly. Satcom systems are vulner-able to both radio frequency and magneticinterference. Satellite television receivers oper-ate in the 1.5 GHz to 1.66 GHz frequencyspectrum, and they can cause interference withcellular telephones (either 850 MHz or 1.9GHz) and GPS (1.5 GHz). However, interfer-ence goes both ways: the GPS or cell phonecan also interfere with television reception.

Other satellite voice and data systems, suchas the Inmarsat Mini-M system, also operate inthe 1.5 GHz to 1.66 GHz range, and areequally susceptible to cross interference. In bothcases radar scanners can cause interference,depending on the specific operating frequency.


All satcom receivers use fluxgate, or elec-tronic, compass sensors to help the antennatrack and aim toward the appropriate satellite.In some units this sensor is mounted underthe same dome as the antenna, while in othersit is mounted elsewhere, typically under set-tees, behind panels, etc. No matter where thesensor is mounted, however, make sure it is farenough away from sources of magnetic inter-ference, including devices with permanentmagnets or electromagnets, high-current-drawDC conductors, and large ferrous objects.Remember that compass sensors (and GPSantennas) must be mounted as close to boththe port-starboard and fore-aft centerlines ofthe boat as possible to minimize the effectsof the boat’s pitch and roll and to provide thesensor with as much stability as possible.

Finally, the NMEA electronic equipmentinstallation standard recommends that a plac-ard be placed near this satcom sensor thatreads: “Magnetic Compass Area! Do NotInstall Or Store Magnetic Material Within3 Ft.” That recommendation nicely sums upthe concerns with magnetism.

The systems listed in Table 14-2 are strictly satellite communications options. DirecTV, a popularland-based satellite company, is one of the most common service providers for boat-based systems aswell. Manufacturers of satellite television equipment include:

King Controls, www.kingcontrols.comKVH, www.kvh.comRaymarine, www.raymarine.comSea Tel, www.seatel.comShakespeare, www.shakespeare-marine.com

The two largest satellite radio service providers in North America are:

Sirius, www.sirius.comXM Radio, www.xmradio.com

SATELLITE TELEVISION AND RADIO


Troubleshooting Satellite SystemsA proper satcom installation typically con-cludes with a series of calibration tests for thefluxgate sensor and operational tests for thereceiver. These tests are for electronics special-ists only, however, and are therefore beyondthe scope of this book.

However, as the owner or electrical techni-cian, your troubleshooting should confirm thebasics of a proper electrical installation as follows:

• wiring links between the system’s compo-nents are in order

• power is getting to the devices• any manufacturer-required grounding is

in good order • sources of RFI and EMI have been avoided

or eliminated

There are many systems available world-wide, as shown in Table 14-2. The onus is onthe electronics technician to be aware of thespecial needs of this equipment. Aside fromminor troubleshooting of the sort I’ve describedabove, most issues related to satcom equipmentare best dealt with by factory-trained specialists.In fact, many warranties require that the equip-ment only be installed by such specialists.

POSITION-FINDINGSYSTEMS

Over the course of just a few decades, naviga-tion has evolved from paper charts, dead reck-oning, and sextants to almost universal pene-tration of electronic methods. It began withsystems like Loran-A and Loran-C, and earlysatellite navigation (satnav), which gave a posi-tion fix every 90 minutes or so (if you werelucky). Then electronic position findingevolved to become virtually synonymous withthe satellite-based global positioning system(GPS), which gives us essentially real-timeinformation of phenomenal resolution.

The first GPS units became available toboaters in the late 1980s. They held a lot ofpromise, but were extremely expensive, and thefact that the full satellite system was not in placeleft voids in the coverage at certain times of theday in some geographic locations. At one pointin the early 1990s, the system seemed to beworking quite accurately. Then the Gulf Warbegan, and the U.S. government imposedSelective Availability (SA), which “detuned” theinherent accuracy of the GPS system for mili-tary reasons. During this time, however,enhancements were introduced to recover theinherent potential accuracy of GPS. Theseincluded Differential GPS (DGPS), which wasa supplemental shore-based radio system simi-lar to Loran-C, and WAAS (wide area augmen-tation system), a system of additional satellitesand ground stations that corrected GPS signals,further improving the system’s accuracy. SA wasturned off by President Clinton in 2000, but itcould return at any time.

As of this writing, the industry seems tohave settled on WAAS-enabled equipment,which is accurate enough to pinpoint yourlocation anywhere on earth to within 3 meters(about 10 feet) 95% of the time.

Today, GPS is the heart of virtually everyelectronic navigation system and is perhaps oneof the most interfaced devices on board. To useNMEA parlance, GPS is the primary “talker”aboard most modern boats, sending its data tomany other devices—the “listeners.” It’s quitecommon to have a single GPS receiver linked toone or more repeater displays, an autopilot, aVHF radio, radar, and a computer. Proper GPSinstallation and performance is key to both thefunctionality of many devices on board and thesafety of the boat and crew.

GPS Installation and Troubleshooting

The major GPS installation component is itsantenna, so we’ll cover that here, instead of in

Chapter 16 where other antennas are dis-cussed. Compared to many other electronicsystems on board, GPS is generally not sensi-tive to outside interference (although there aresome specific instances discussed below). This,at least, makes installation relatively easy.

A GPS receiver is a line-of-sight device. Butunlike VHF radios where the line is horizontal,the GPS line of sight is vertical. Its small, typi-cally hockey puck–shaped antenna must have aclear view of the sky to receive signals from theGPS satellites. Anything blocking the sky viewalso blocks signals, so careful attention must begiven to the location of the antenna “puck.”

Think about ergonomics here as well. I’verecently noticed an alarming trend of mount-ing GPS antennas on the cockpit coamings ofsailboats. Recently, I was on board a test boatwith just such an antenna mounting. Whilebeating down Chesapeake Bay, I noticed thatthe GPS unit was no longer displaying posi-tion or speed over ground. I looked aroundthe cockpit and, sure enough, a crewmember

was sitting on the little hockey puck, blockingits reception of satellite signals!


• Match the brand and model number ofyour GPS antenna with the receiver andthe cable harness connecting them.

• Position the GPS antenna as follows:

out of the way of people and normalon-deck traffic areas

with a clear view of the sky above

as close as possible to the boat’s centerline

not too far aloft; the boat’s rolling andpitching motion, amplified byincreased height abovedeck, will tendto send the GPS a bit crazy trying tofigure out where it is

• Because the cable is a proprietary one, donot alter its length.

• Flake excess cable in large ellipticallyshaped loops. Do not coil tightly. (Vendors

GPS antenna

A cockpit coaming is a really poor mounting location for a GPS antenna——right wherecrew can sit on it and block satellite reception. Not only is it vulnerable to beingstepped on and kicked, it may also snag jibsheets, and it even interferes with thecoaming’s otherwise comfy function as a seat or armrest.



typically identify minimum radius bendsfor cabling in their instruction manuals.)

• Secure flaked cable a sufficient distance(usually 18 to 36 inches) from potentialsources of electrical interference.

The matter of flaking the cable versus coil-ing is one of the most common problems seenin the field. Coiling these cables creates anundesirable ancillary antenna—i.e., separatefrom the actual antenna at the end of thecable—that easily receives interference.

If the GPS has an additional differentialantenna hookup onboard, interference canbecome a real concern. DGPS operates in the150 kHz to 500 kHz spectrum and is suscep-tible to the noise generated by the varioussources of RFI already discussed. Appropriateseparation (again, typically 18 to 36 inches)needs to be maintained between these emittersand the differential antenna.

In contrast, the operating frequency ofnondifferential, or WAAS-enabled, GPS is1.5 GHz. Most small boats don’t have any-thing on board that approaches that frequency,except for cell phones. As noted earlier, cellphones operate at either 850 MHz or 1.9 GHz.Basic GPS operates roughly in the middle ofthat spectrum, so a cell phone interfering witha GPS is a real possibility.

Although still rare on anything but thelargest boats, satellite television is becomingincreasingly popular, and its 1.5 GHz to1.66 GHz frequency spectrum is close enoughthat it could also interfere with GPS.

Volts, Amps, and TemperatureGPS is much more forgiving of variations inthe DC power supply than some of the otherequipment we’ll discuss. The voltage operatingrange is usually from about 10 V to 16 V(although you should always confirm this withthe manufacturer’s installation documentation).Current draw typically ranges from milliamps

for the smaller units to as much as 4 amps onsome of the larger, color chartplotter units withbright backlighting. Therefore, wiring forpower to GPS systems does not impose anyunusual demands. Some units have a chassisground lug, and others don’t. Use it if it’s there,and don’t worry about it if it isn’t.

Likewise, cooling isn’t much of a problem onmost smaller units, as they do not generate muchheat. On some of the larger displays, the LCDbacklighting can generate a fair amount of heatbuildup. I use a simple rule of thumb: If there are

GPS can be used on board with a computer. Thecomputer serves the chartplotting function with higherpower than a typical integrated chartplotter. The GPS unitcan be a stand-alone fixed sensor without its own display,or a GPS chartplotter. The computer accepts data from avariety of sensors in this configuration through a multiplexer(MUX). The multiplexer sequentially forwards the data tothe computer from each source. Wind, depth, watertemperature, radar, and GPS data can all be presentedon the computer screen using navigation and other soft-ware. The computer then can direct information and com-mands to the autopilot. Note that power and ground linesare omitted in the diagram for simplicity. (Reprinted withpermission from GPS for Mariners by Bob Sweet)

cooling fins on the back of the display, heat is aconcern, so as an installer I need to think aboutgetting air circulation around those fins.

Interfacing GPS with Other EquipmentInterfacing GPS with other equipment, such asautopilots and repeater displays, can be one ofthe biggest challenges in working with GPS,although this is generally less of a problem if theother units are supplied by the same manufac-turer. The GPS unit calculates a lot of data asyour boat moves through the water, then itupdates the data in real time, and sends it over anetwork to other pieces of electronic equip-ment, such as a DSC-equipped VHF, auto-pilot, and radar display (see illustration oppo-site). We’ll look further at networking in Chapter17, but specifically as it applies to GPS, thereare several things to point out here.

First is the network protocol. Much of thishas to do with the digital language the variousdevices in the network are using. The twomost common networking protocols for GPSare NMEA 0183 and NMEA 2000 (see alsoChapter 17). There are several versions ofNMEA 0183, however, and even within thesestandards, the “sentence structure” of the digitalmessages may differ from one manufacturer toanother. Some manufacturers don’t use NMEAat all, but go with proprietary networkingschemes based on Ethernet, a common officenetwork, or on controller area network (CAN),a common automotive architecture.

The bottom line is that it can be difficult toachieve complete compatibility between devicesfrom different suppliers. Some data may transferreadily through the network and some may not.

The only way to ensure compatibility is tolocate the equipment’s network version numberand specific sentence structures in the specifica-tion manual for any given piece of equipment.Then compare this information to specificationsfor the piece of equipment you are attemptingto link via the network. Obviously, if you do this

COMMONLY USED NMEA 0183SENTENCE CODES

APB = autopilot, format BBOD = bearing, origin to destination waypointBWC = bearing and distance to waypoint (great circle)BWR = bearing and distance to waypoint (rhumb line)DBT = depth below transducerGGA = GPS fix dataGLL = position in latitude and longitudeGSA = GPS DOP (dilution of position) and active

satellitesGSV = satellites in viewHDM = magnetic bearingHSC = command heading to steerMTW = water temperature in degrees CelsiusRMB = recommended minimum navigation informa-

tion when a waypoint is activeRMC = recommended minimum specific GPS/transit

dataRTE = route information in active routeVHF = water speed and headingVTG = track made good and ground speedVWR = relative wind direction and speedWCV = waypoint closure velocityWDC = distance to waypointWDR = waypoint distance (rhumb line)WPL = waypoint locationXTE = cross-track error, measuredXTR = cross-track error, dead reckoning

before buying a new piece of equipment, you’llhave the luxury of working with equipmentthat’s designed to work together.

Some examples of the specific codes foundin the sentences that talkers and listeners mustbe able to transmit and receive are shown inthe sidebar.

It may be possible, however, to networkdevices that utilize different protocols or lan-guages with ancillary “black boxes” that areinstalled between talkers and listeners. Basicallythese boxes are translators, whose purpose is to



take the language the talker is using and trans-late it for the listener. You may also find anadditional black box, called a multiplexer, thatwill distribute data to multiple instruments.See the sidebar on page 191 in Chapter 17 formore on networking terminology.

How do you use them? One examplewould be to connect a combiner/multiplexerbox to a piece of NMEA 0183 equipmentwith a computer via a RS-232 port, or connectto a Raymarine device that is networked viathat company’s proprietary SeaTalk system.

RADAR

Similar to satcom, radar may require the ser-vices of a manufacturer-trained specialist to setup the initial calibration and tuning of the unit.This need will depend on the boatowner’sfamiliarity with radar. In many cases, a trainedprofessional is the best choice for an initial run-through of the unit’s operational characteristics.Although all these units operate on the same

principles, software access, system menus, andcontrol functions can be confusing at first, andoften the instruction manuals provided withthese units are absolutely confusing!

This does not, however, preclude boat-owners or marine electricians from performing aradar installation if they desire. Most radar unitsmarketed for the recreational boating market are“pre-tuned” and calibrated at the factory, sothere are only a few issues to deal with.


• You must use the cabling provided by theequipment manufacturer.

• You must not alter the length of thosecables. If you need longer cables thanthose supplied, all the manufacturers offeroptional longer cables, which you mustuse to ensure proper operation.

• Consider the ergonomic issues alreadydiscussed—viewing angle, displaysettings, etc.

inverter display/monitor

tank level gauge

VHF radio

Raymarine interfacetranslator box

battery monitor

Black boxes like this one are often required to allow talker and listener devices to communicate across differ-ent protocols or languages. While not perfect, they meet the need.

Perhaps the biggest concern with radar isthat the highly focused beam of energy in themicrowave frequency range it transmits maybe harmful to people on board the boat, andalso can affect other onboard electronicequipment. Most marine radars units installedon recreational boats are X-band units, whichoperate in the 8 GHz to 12 GHz frequencyspectrum. Some larger commercial craft mayalso have S-band radar units, which operate inthe 2 GHz to 4 GHz spectrum.

The matter of whether or not radar isharmful to people on board the boat is debat-able. Cases of testicular cancer, cataracts, andeven behavioral changes have been attributedto exposure to radar beams. After analyzingdata provided by the World Health Organiza-tion (WHO), it seems clear to me that youwould have to be literally sitting in front of theradome, say within 3 feet, for extended periodsof time to cause any ill effects. And even that isnot certain. In the United States, groups suchas the National Council on Radiation Protec-tion (NCRP) are researching the possible car-cinogenic, reproductive, and neurologicaleffects of human exposure to the levels of radi-ation emitted by radar units. One thing we doknow for sure is that all the radar vendors willdiscuss the potential safety hazards associatedwith exposure to the radar beam and makeinstallation suggestions that will minimize thepossibility of this occurring.

As far as interference with other elec-tronic equipment is concerned, WHO sumsit up like this: “Radars can cause electromag-netic interference in other electronic equip-ment. The threshold[s] for these effects areoften well below guidance levels for humanexposure to RF fields. Additionally, radarscan also cause interference in certain medicaldevices, such as cardiac pacemakers and hear-ing aids. If individuals using such deviceswork in close proximity to radar systems they

should contact [the] manufacturers to deter-mine the susceptibility of their products toRF interference.”

Ensuring Electromagnetic Compatibility

Radar manufacturers are concerned about elec-tromagnetic compatibility (EMC), which isthe ability of electronic equipment to operatein proximity with other electrical and elec-tronic equipment without suffering from, orcausing, impaired performance. For our pur-poses, it is essentially synonymous with EMI.Improper installation of a radar set will almostcertainly guarantee problems with otherequipment as well as with its own perform-ance. So we need some commonsense guide-lines to help us achieve compatibility:

• Keep radar and its connecting cables atleast 3 feet (1 m) from any other trans-mitting equipment or cables carryingradio signals, such as VHF radios. In thecase of SSB radios, double this separatingdistance because SSBs are more powerfulthan VHF radios.

• Keep other antennas and electronicequipment out of the radar beam’s pathby at least 6.5 feet (2 m). The radar beamtypically spreads about 12.5 degrees aboveand below the radiating element (scanner)on the radar.

• Radar needs a power supply separate fromthat of the engine starting motors. Equipit with its own battery or a UPS device(such as the Newmar unit mentioned inChapter 13) to prevent the unit fromblinking out and having to restart.Voltage spikes and/or drops that occurduring engine cranking will often beoutside the voltage-operating parametersfor the radar.

• If the cabling is equipped with a noisesuppression ferrite as shown in the photo,



do not remove it when pulling cablesthrough the boat during installation. Ifthe cabling has to be removed, it must bereassembled in exactly the same way andin the same position.

These considerations are universal andshould be carried out for all radar systeminstallations.

Power Supply

As with satellite communications systems,radar systems have multiple power-supplyrequirements: one to the display unit orreceiver, one to the antenna or scanner, andpossibly one to the scanner’s motor drive. Dif-ferent equipment manufacturers take differ-ent approaches; some of them use multiple

Two typical power cord ferrites. These small devices areincreasingly found on wiring harnesses and power supplycords on modern equipment, and they are crucial in help-ing to minimize interference effects.

display unit

distribution panel

multiplexer

GPS antenna

radome unit

fluxgate compass

NEMA

12 V supply

12 V supply 12 V supply

junction box

NEMA cable

A typical radar system layout with peripheral electronics. This is a relatively simple point-to-point arrangement. Radar canalso be integrated into an onboard network to share data with several other devices, such as autopilots, repeater dis-plays, and chartplotters.

power sources, and others use a single, splitsource. In the end, the manufacturer’s wiringsystem diagram is the only practical way tofind the appropriate power supply.

Power supply conductors are often bun-dled into a harness with the signal-carryingconductors. Remember, it is essential to usethe manufacturer’s cable harness. If you haveto alter the cable length, some manufacturers

offer harnesses in a variety of lengths toaccommodate different installation require-ments. Pay close attention to any specifiedminimum bend radius. These harnesses maynot come supplied with fuses to protect themin the event of an electrical overload orshort circuit; be sure to use the manufac-turer-recommended fuses and locate themwhere specified.


course computer

in-linepowerswitch

integral10 A fuse Installing Depth

Sounders, WeatherSystems, and Autopilots

Depth sounders, weather monitoring systems, and autopilots are three areas inmarine electronics where we have seen dramatic improvements and increasedsophistication over the last ten years. Depth sounders and particularly fishfinders

have evolved from the old Si-Tex paper drum recording units that were a mainstay amongserious fishermen for some time to the full-color LCD display units of today. Side-scanning and even forward-searching depth-sounding capabilities are now available forthose who feel the need for that level of underwater probing. As for weather monitoring,the old wind vane and cup masthead sensors in use for decades are being replaced withultrasonic sensors that have no moving parts to wear out or get broken by errant seagulls.Autopilots have gotten more powerful, and draw less electrical current than they used to,enabling offshore cruisers to consider using electric autopilots instead of wind vanecontrolled self-steering systems (which are always a concern due to battery capacity limi-tations). They are now relatively easy to interface with GPS, thus not only automaticallysteering your boat, but taking you where you want to go quite accurately.

DEPTH SOUNDERS

Depth sounders and fishfinders are echo-sounding systems used to determine the depth ofwater under your boat or to find targets (many units combine the two systems). They aresimilar to most of the devices discussed in Chapter 14 in that they have a display, transmitand receive signals, and use cables. They are different in that instead of an antenna, depthsounders have a transducer, which for most recreational systems transmits at a frequencyof 50 kHz or 200 kHz. (Lowrance—www.lowrance.com—recently began advertisingdual-frequency units transmitting at 80 kHz or 200 kHz.)

Depth sounders can be simple devices that only tell you the distance to the bottom orthey can be feature rich with, for example, various alarms (shallow/deep water, warning),forward scanning, and the ability to provide pictures or a graphic contour of the bottom.Some include SeaTalk or NMEA capabilities and can be networked to your autopilot,GPS, radar, or chartplotter. They range in price from $100 to $3,500.

C H A P T E R

15


1 5 7

Depth sounders and fishfinders can beamong the most troublesome of all categories ofmarine electronics because they are sensitive toboth over- and undervoltage situations. In addi-tion, the transducer that sends and receives sig-nals from the bottom can be fouled by marinegrowth and needs periodic cleaning. It alsomust be carefully installed in the correct loca-tion on the boat’s bottom to ensure maximumfunctionality. To keep these devices performingproperly, a first-class installation is paramount.

Displays and Cables

Depth sounders have four types of displays:LCD screen (color and black and white), CRT(similar to a television screen), paper graph, andspinning wheel flasher. When choosing a depthsounder or fishfinder, be sure to check the read-ability of the screen, especially in daylight.

The cable that connects the transducer to thedisplay is carefully impedance matched to the sys-tem, so under no circumstances should you alterits length or wire gauge. Doing so would severelyaffect the performance of the system. Wheninstalling, carefully route the cable to avoid inter-ference from other electrical equipment.

Transducers

The transducer is mounted on the bottom of theboat. Its purpose is to convert the electrical signal,or pulse, from the depth sounder to a sound,called a ping, and transmit it through the water.The sound wave travels until it hits something,and then echoes back. The transducer capturesthe echo, converts the sound back to an electricsignal, and sends this back to the depth sounder.This process of transmitting, echoing, and receiv-ing can happen up to forty times per second.

Transducers on simple, numerical depthsounders are intended to point straight down (ornearly so), while on the most sophisticated unitsthey may have sideways- or forward-transmitting

installing depth sounders, weather systems, and autopilots

compare:

0’

200’

600’

1,200’

1,800’

2,100’

2,400’

2,700’

3,000’

50 kHz 200 kHz

The beam of a high-frequency (200 kHz) depth sounder is narrow, cov-ering a 10- to 15-degree arc. This is good for close focus on the bottomand will give maximum bottom detail. At 50 kHz, the beam is wider andgenerally better for scanning greater depths and providing a broadview with fewer details. Another consideration is power output. A1,000-watt unit can reach greater depths than a 600-watt unit.

capabilities, enabling you to see what’s underwa-ter ahead, or to port and starboard.

As the ping, or sound wave, is transmittedinto the water by the transducer, it forms a cone-shaped beam, which can be as narrow as 15degrees or as wide as about 45 degrees (as shownin the illustration on page 157). Some of themore sophisticated units, such as those availablefrom Interphase Technologies (www.interphase-tech.com), can scan through even wider arcs.

In order to receive the echo, the transducermust be oriented correctly on the hull accord-ing to the manufacturer’s guidelines. Mostoften, some sort of fairing block is needed toaim the beam correctly.

Mounting a TransducerTo make the most of your depth sounder/fishfinder, the transducer must be mounted inthe best location for your boat (i.e., sail or


power). We’ll cover general guidelines first, thengo into some specifics.

• As much as possible, mount the trans-ducer so it has an unobstructed path forthe beam.

• Mount the transducer so it will be sub-merged at all times while underway. Thismeans powerboat owners must take thelocation into account when the boat is upon plane.

• Do not mount a transducer in the flow ofturbulent water, such as near a prop orbehind a strake or through-hull flange.For inboard boats, do not mount it nearthe propeller shaft struts or raw-waterintake fittings.

paddle wheel

A typical transducer installed on a fairing block on apowerboat. The joint between the transducer and the fair-ing block is difficult to see because antifouling paint hasfilled the seam, but the fairing block represents about50% of the profile surface. This particular transducer alsoincludes a small paddle wheel that drives a knotmeterfunction on the same instrument.

Installation of a transducer. Note the fairing blocks bothinside and outside to create a level mounting surface and(if this were a through-hull or seacock) spread any acci-dental load (e.g., being hit by gear or trodden on). Notealso the generous amounts of bedding compound.(Reprinted with permission from Nigel Calder’s CruisingHandbook by Nigel Calder)

fairing block

fairing block

Transducer mounts on sailboat hulls can betricky because a long keel is more likely tointerfere with the cone-shaped beam as itexpands downward from the transducer. Eitherforward or aft of the keel, rather than to eitherside of it, is often the best location. Powerboatswith prominent keels can also have this problem.If you have a side- and/or forward-scanningunit, it must be mounted on the centerline,forward of the keel.

Transom-mounted transducers are typi-cally used on powerboats due to their relativeease of installation. However, do not place atransducer directly in front of an engine drive’slower unit, where the disturbed water flowcould interfere with engine cooling and mightcause propeller cavitation as well. It is advis-able to offset it by as much as 18 inches. Onsingle-engine installations, this means thetransducer will be away from the boat’s center-line, while on dual-engine installations, thecenterline may be the best location.

Yet another mounting option is to glue thetransducer to the inside of the hull. In most

1 5 9installing depth sounders, weather systems, and autopilots

cases, the transducer will transmit and receive itssignal directly through the hull material; in oth-ers, it is mounted inside a fluid-filled chamber(usually filled with compass fluid or a 50-50blend of antifreeze and water), which is mountedto the inside of the hull. These chambers areavailable commercially, but they can also behome-built from 4-inch ID (inside diameter)PVC pipe cut to the hull contour and sealed ontop with clear Plexiglas and silicone sealer. It usedto be easier to replace transducers mounted inthis fashion, but with modern adhesives, there’sno longer much of an advantage.

For an inside-the-hull installation to beeffective, the transducer must rest on a solidmass of material. Solid GRP (glass-reinforcedplastic—i.e., fiberglass) and wood hulls workwell, but cored laminates do not. Some trans-ducers may work through some metal hulls,but it’s advisable to test the transducer firstbefore making the installation permanent.

Whether a transducer is mounted in achamber or to the hull, the transducer faceneeds a “solid” surface for its vibrations to be

This transom-mounted transducer on a dual-outboard boat is located to port of theboat’s centerline to avoid disturbing the water flow to either of the lower units.

cable

transducer

centerline

transmitted. You must make an airtight, void-free bond between the transducer face and thehull surface. Use a glob of silicone caulk or3M 4200 adhesive sealant, being sure to use asufficient amount of the adhesive to create asolid mass of material between the entire faceof the transducer and the hull. Do not use 3M5200 for this purpose, or you will have a verydifficult time removing the transducer whenyou want to replace it.

Installation and Troubleshooting

Now that we’ve determined the location andmethod of mounting the transducer, let’smove on to installation and troubleshooting.

CablesAs noted earlier, the cable is impedancematched to the system and altering its lengthwill affect system performance. Route cablesso as to avoid EMI and sharp bends.

Intermittent problems with depth soundersare often related to cable failures. A “wiggle”test of the entire length of cable will help youidentify loose or broken connections under thecable insulation.

To perform a wiggle test (which will workon any long cable runs):

1 Run the system while flexing the cableitself, particularly its termination points.

2 Have a partner watch the display and seeif it remains constant.

3 If the display blinks out while you’re wig-gling at a certain point, you have found abad connection or break in the wire(s).

In most cases, repair will require replacingthe cable with a factory-supplied unit. In otherunits, the cable may be permanently con-nected to the transducer, so replacing theentire transducer/cable assembly may be youronly option.

Warning: Never disconnect the cablefrom the display while the system is turnedon; it can produce a pronounced electricalarc. Power down the unit before discon-necting the transducer cable.

Power SupplyDepth sounders are quite sensitive to power sup-ply. Most operate in the 10 V to 16 V range andrequire 1 to 4 amps of current. Symptoms ofexcessively high or low voltage vary with the com-plexity of the unit. With a simple numerical read-out sounder, you’ll encounter errors in depthreadings or a blinking display; with a fishfinder,you’ll get garbled and shifting or random bottomcontours. The obvious troubleshooting approachis to test and confirm voltage supply to the dis-play unit with your DVOM.

InterferenceAs with all electronics, you must also be awareof the possibility of interference. In spite ofcable shielding, cross-conductor interferenceoften occurs, especially on modern boats inwhich numerous cables are crowded togetherin conduits or wire trays. Because the cableconnecting the transducer to the display is afixed length, flake excess cabling in an out-of-the-way location (see Chapter 14). However, ifyou must coil the cable, be sure to locate thecoil far from any of the high-output emittersidentified in Chapter 9.

If you suspect interference (after first con-firming the quality of the voltage supply andreturn ground to the system), the only way toisolate the source is through process of elimi-nation: With everything else on the boatturned off, including the engines, check thedepth sounder for normal operation. Then,turn on one circuit at a time and see if the prob-lem appears. After you’ve isolated the culprit,establish an appropriate zone of separationbetween the offending component or circuitand the transducer cabling, as described in


Chapter 9. You may have to reroute the trans-ducer cable to correct the problem.

Remember that potential interference cutsboth ways. Some manufacturers recommendthat the display unit be mounted at least 3 feet(1 m) away from any steering compass. This ishard to achieve on smaller boats with tight con-soles, such as center console fishing boats. Ifyour boat layout requires a smaller zone of sepa-ration, then before you install the unit, confirmthat operation of the depth sounder/fishfinderwill not cause compass deviation.

FailureTransducers are subject to failure, but sincethey are a sound-producing device, you caneasily determine if they are functioning by sim-ply listening to them. I typically touch one endof a long wooden dowel or a long screwdriverto the transducer either inside the boat, or ifthe boat is out of the water, on the face of thetransducer itself. For an externally mountedunit on a boat in the water, you can touch oneend of a long dowel or boathook to the unit.With the system turned on, put the dowel orscrewdriver handle to your ear. If it’s working,you should hear a distinct clicking sound.

More empirical results are possible if themanufacturer has provided specific electricaltests to perform at the display end of the cableharness assembly. However, product-specificliterature is necessary to identify the right gangplug pin ends and appropriate procedures andresults for these tests.

In a nutshell, troubleshooting depth-soundingequipment involves many of the same proce-dures and limitations as other gear types alreadydiscussed, namely:

• Check the voltage quality under all condi-tions, including during engine cranking.

• Confirm the transducer is properlymounted and oriented.

• Ensure cables and connections are soundand separated by sufficient distances fromother electrical devices to rule out EMI.

For problems beyond the scope of thesetests, consult an electronics specialist. In mostcases, problems with a depth sounder’s inter-nals are generally resolved by simply replacingthe transducer, display, and/or cable.

WIND- AND WEATHER-MONITORINGINSTRUMENTS

In terms of frustration, instruments for monitor-ing wind direction and speed were near the topof my list for years. This probably reflects myexperiences as a navigator on high-performanceracing sailboats. Both crew and owners wantedabsolutely precise tack-to-tack readings—a goalthat was often hard to achieve back then. In theend, if I got it within a few degrees, I felt I had agood day.

The calibration of wind and weatherinstruments has always been a real chore, andcertainly beyond the normal realm of themarine electrician or boatowner. There wasnothing simple about this process. Unless youfollowed the manufacturer’s specific calibrationinstructions, which were often about as clear asreading a manuscript written in hieroglyphics,you didn’t get very far.

Most of the problems centered onupdrafts—air that flows up a sailboat mast,spilling off both the headsail and the mainsailat the top. An updraft creates turbulent air,which disrupts both the traditional wind vanepointer that provides directional data and thewind cups that provide velocity data. Addition-ally, these sensors are electromechanical andsubject to the usual problems of such deviceson a boat. An errant seagull colliding with thevane or wind cup and the failure of a bearingare not uncommon problems.


In recent years, equipment has improvedconsiderably with offerings from companiessuch as Brookes & Gatehouse (B&G, www.bandg.com) and Airmar (www.airmar.com).For example, Airmar recently introduced anew weather-monitoring sensor/transducerthat promises to change the way boatersmonitor barometric pressure, wind direction(true and apparent), wind speed (true andapparent), air temperature, dew point, rela-tive humidity, and even wind chill tempera-ture and GPS position data (see below). Thesensor is an ultrasonic device, with no mov-ing parts. All functions are displayed on aPC, which also can be interfaced with chart-plotters, autopilots, and other devices. Plusit is compatible with NMEA 0183 andNMEA 2000 devices (see Chapter 17),which also permits the use of conventionalinstrument displays (as long as they are NMEAcompatible). They are not cheap, however,costing around $1,000.

WeatherStation Layout

Airmar’s WeatherStation system consists of asensor, a power supply to the sensor, and aconverter unit that interfaces with a laptopand is powered by the computer’s USB supply.An optional piece of equipment called a com-biner lets you connect to a laptop and NMEAdevice simultaneously.

Installation involves the same considera-tions as always: pay attention to sensor posi-tioning (see below) and cable routing, andensure the device has a sufficient power supply.In addition, you will need to install overcurrentprotection for the power feed conductors, basedon the manufacturer’s recommendations.

Sensor placement is critically important;parameters are as follows:

• Proper orientation in the fore-and-aftplane is a must for the unit’s directionalsensing capability to work.


• To accurately sense airflow velocity anddirection, it must be mounted in a locationthat ensures unobstructed and undisturbedairflow across the sensor surface. Airmarrecommends a minimum of 6.5 feet (2 m)of clearance between the sensor and anyobstructing object. This will not be an issuewith sailboat installations if the sensor is atthe top of the mast, but it could be a realchallenge on many powerboat installations.

• Placement relative to other transmittingantennas is also important as they candisturb airflow and create turbulencenear the sensor.

• The unit is also a GPS sensor, so interfer-ence from other antennas is possible (seeChapter 14).

The WeatherStation’s total power consump-tion will depend on its configuration. If thesensor is connected to a PC, then obviously thePC will require a power supply. If NMEA-compatible displays will be used, then eachwill need its own power supply. The sensoritself operates in the 10 VDC to 16 VDC

Typical configuration of an Airmar WeatherStationinstallation.

battery

laptop

AIRMAR CONVERTER

WeatherStation

range and requires only 0.5 amp of current, soeven for masthead-mounted sensors, theweight of wiring aloft will be low.

As with all wind-machine instruments,especially those with long wire runs up sailboatmasts, you must install cables carefully, usingproper support and strain relief at the mast-head to ensure acceptable service life. WhileAirmar suggests that cable lengths not bealtered, they do provide specific guidelines formaking connections and attaching RFI shield-ing if you have to remove a cable connector tofacilitate routing through tight openings.

For the average boatowner or marine elec-trician, troubleshooting this system will focuson confirming voltage and ground integrity.The TDR tool (Chapter 3) will be useful toconfirm wiring harness integrity.

AUTOPILOTS

Autopilot installation and troubleshooting canbe critical to the safety of your boat and crew.And depending on your boat, you may needthe combined efforts of an electrical installer(possibly you), an electronics specialist, and amarine mechanic.

I say mechanic, because if the boat hashydraulic steering you may need a mechanic tomount and interconnect the hydraulic steeringpump that is part of the autopilot system and isintegrated electronically to the autopilot con-trol box. Depending on the system you choose,the autopilot pump may replace the existinghydraulic steering pump. In any case, theautopilot pump will become the driving forcefor the hydraulic ram or actuator at the rudder.

In nonhydraulic steering systems that relyupon gears or cables (or even direct tiller-to-rudderstock connections), a mechanical actuatorservo must be linked to the existing steeringsystem. (You may need a mechanic for thisalso, depending upon your skills and/or thoseof your electrical technician.)

The illustration highlights several key points:

• The RF ground serves to minimize theeffects of any EMI with the coursecomputer. Equipment vendors’instructions for the connection of thisground must be followed to the letter.

• The data cable interface harness may besplit farther away from the coursecomputer to provide and receive datafrom NMEA-compatible devices such asa GPS, and/or to connect to a proprietarynetwork like Raymarine’s SeaTalk orFuruno’s NavNet.

• This same harness may also containcabling to feed a system alarm.


Autopilots are an interesting mix of electronic, electrical, and electro-mechanical components that must be integrated with the boat’s onboardnavigation system to function properly. The system shown is for a boatwith hydraulic steering. On a boat with mechanical steering, the pump inthe illustration would be replaced with an electric servo and a mechani-cal connection to the steering system.

battery

course computer

to GPS and alarm system

in-linepowerswitch

NEMA interface(may also be proprietary)

integral10 A fuse

integralferrite

RF ground plate

autopilotpump

Additionally, it is imperative that the elec-tronics specialist involved with any installationcarefully check the interface protocols betweenthe autopilot computer and the GPS receiverto ensure that all the necessary data will betransmitted and received.

Autopilot Installation

Most autopilots will function in a 10 V to16 V range without incident. The 3% maxi-mum voltage drop guideline applies here aswell, so be careful to consider circuit lengthwhen calculating power feed wiring require-ments. Autopilots are fairly heavy power con-sumers, drawing anywhere from about 4 ampsto as much as 10 or 12 amps, depending onthe system. This high current draw is due tothe hydraulic pump/motor combination,which is constantly working when the systemis on, and motors by their very nature areheavy electrical consumers.

Note: Many of the manufacturer-suppliedelectric motor drives are not rated for ignitionprotection. These drives should not be installedin engine room spaces or fuel tank storage areason gasoline-fueled boats. Both the U.S. CoastGuard (in CFR Title 33, Part 183, Subchapter I)and ABYC Standard E-11 require that allinstallations in these areas be rated as ignitionprotected. Keep in mind that the CFR stan-dards are mandatory; the ABYC standards areconsidered voluntary.

Unfortunately, I see this requirement over-looked on many boats, and it represents a serious

fire hazard if a fuel leak ever develops on thoseboats. Check with the equipment manufacturerthat the motor drive is ignition protected if youplan to install it belowdeck on a gasoline-fueledboat. If it isn’t ignition protected, you shouldswap it out for one that is.

Because autopilots rely on electric motors,proper rating and placement of overcurrentprotection for the circuit and/or motor areimportant considerations for the marine elec-trician. In fact, this is true for any electricalequipment installed on board, and the bestcourse is usually to follow the manufacturer’srecommendations to the letter.

Finally, for the mechanic, it’s important thatwhatever the steering actuation device is—motor-driven lever action or hydraulic pump—it must be securely mounted to the boat’s struc-ture. Think through-bolts, not self-tappingscrews!

While it’s best to leave the final testing andcalibration of autopilots in the hands of theelectronics specialist, you can provide the samebasic quality control functions as with otherequipment:

• Make sure the system computer is mountedas far as possible from any RFI or EMIemitters.

• Check for interference by running the boatunder autopilot and, one by one, operatingall other electrical equipment. Obviously,this test should be done in open water incase interference does occur that causes theboat to suddenly change course.


C H A P T E R

16Coaxial Cable andAntennas

Unlike most other signal and power wiring, coaxial cable (or coax) is not merely aconduit between devices; it represents an inherent part of most marine antennas,and needs to be addressed as a critical component.

COAXIAL CABLE BASICS

We need to focus on coaxial cable selection and installation requirements since coax is theconnection between antennas and their transceivers; there are quite a few commonly usedvariations of coax cable available; and signal losses through it can diminish the performanceof a transceiver, or even render it almost useless. After voltage and amperage problems, lossthrough this vital link is perhaps the biggest factor in poor equipment performance.

Coaxial cable is different from the wire and cable used strictly to conduct electricity orlarge amounts of electrical current. And although coax is sometimes used to carry electri-cal power, its more common use, and the one we’ll focus on here, is to carry radio, video,and data signals.

Coaxial cable consists of four layers (see illustrations page 166). In the center is a con-ductor composed of either solid copper wire or stranded copper (commonly used inmarine applications). The core conductor is surrounded by a dielectric material or insula-tor. Surrounding the insulator is the second conductor, a sheath or shield, which can beeither braided copper or a foil. The final layer is the outer jacket (insulation), which pro-tects the cable from the environment and provides some flame retardation.

The signal is carried by the center conductor, while the shield protects the signal fromRFI and serves as a ground. The design is intended to keep the signal in place, so that itwill not “couple” with adjacent wiring routed in the same cable run, and noise from adja-cent cables will not interfere with the signal.

Boat-system installers and troubleshooters have three specifications to be concernedwith: attenuation, impedance, and velocity of propagation.

Attenuation

Coaxial cable will always have some attenuation, which is the amount of signal loss pergiven length of the cable. This value is measured in decibels (dB). The idea is to keep theloss within parameters described later in this chapter.


Impedance

Each type of coaxial cable has an inherentimpedance, or opposition to current (it’s thehigh-frequency equivalent of resistance). Moreimpedance means more attenuation. Interest-ingly, this impedance is not related to thelength of the cable but to the wire gauge of theconductors and the thickness and effectivenessof the insulation between them.

Coaxial cable specifications typically assigna “characteristic” impedance, which is calcu-lated from the ratio of the inner and outer


diameters and the dielectric constant. Assum-ing the dielectric properties of the materialinside the cable do not vary too much over theoperating range of the cable, this impedance isfrequency independent.

The most common impedance values asso-ciated with coaxial cable today are 50 ohm and75 ohm. Usually, the 50-ohm variety is used tocarry radio signals and data (Ethernet), and the75-ohm variety is used for audio, video, andsome telecommunications applications. Theattenuation associated with each of these valuesis related to the frequency of the signals eachcarries. So attenuation and frequency will helpdetermine the best cable choice and ratedimpedance for a given application.

Equipment should be matched to thecable’s impedance. When radio frequencysignals are transmitted through coaxialcabling, the cable impedance is significant indetermining the load of the transmissionsource and the overall efficiency of the trans-mission. Another way of saying this is thatthe source impedance must be equal to theload impedance (often the antenna) toachieve maximum power transfer and mini-mal signal loss. We need to have matchedimpedance values for the transmissionsource, the cable, and the receiving device atthe other end of the cable. Therefore, makesure the correct impedance cable is used forthe application at hand, as recommended bythe equipment manufacturer.

Velocity of Propagation

As we covered in Chapter 3, VOP is a percent-age of the speed of light that describes the speedof current through a cable. Different conduc-tors have different VOP values due to theirinherent resistances to electrical current flow.

However, as coaxial cable ages, its imped-ance changes, and consequently, so does itsVOP value (increased impedance results in lowerVOP). This indicates a general degradation of

copper wire (solid or stranded)

insulation

copper mesh

outer insulation

Coaxial cable construction.

Three sizes of coaxial cable with the inner insulationstripped back to show the center conductor, and the outerinsulation stripped back to show the (somewhat crumpled)braided shield.

the cable and that replacement is in order.Signs of a poor coaxial connection or degradedcabling will be poor radio reception or lowtransmission range.

You can check the state of the cable bymonitoring its VOP with a TDR (Chapter 3).You can identify cable breakdown or failure,or confirm that the cable is stable and withinknown specifications.

CHOOSING COAX FORMARINE APPLICATIONS

In choosing coax cable, we’ll look at three spec-ifications: type, attenuation, and impedance.

Type

Coax is identified by various RG types,including RG-8, RG-213, RG-8X, RG-58,RG-59, and RG-6U, as well as LMR, such asLMR-400. These designators can be a bit con-fusing, but the letters and numbers do havemeaning. We’ll use RG-8/U as an example:

R stands for radio frequencyG stands for government8 represents a government approval numberU represents a universal specification

If the letter A, B, or C appears before theslash (for example, RG-8A/U), it indicates aspecification modification. The only way to becrystal clear on these subtle specification dif-ferences and letter designators is to check outthe website for one of the major coaxial sup-pliers (e.g., Belden, www.belden.com) andcompare the specifications closely.

Table 16-1 lists the characteristics of fivetypes of coaxial cable found on boats:

• RG-58/U is very thin and typically usedonly for interconnecting electronicswhere lengths are short and signal attenu-ation is not a problem.

• RG-59/U is used to connect televisionantennas and cable service.

• RG-8X is typically used to connect VHFand HF antennas up to lengths whereattenuation becomes excessive.

• RG-8/U and RG-213 are both used toconduct maximum power to VHF andHF antennas.

Some letter designators don’t fall underthis set of government rating numbers. A goodexample is the LMR-400 coaxial mentionedabove. In this case, “LMR” is simply a registered

1 6 7coaxial cable and antennas

Specification RG-58/U RG-59/U RG-8X RG-8/U RG-213

Nominal O.D. 3/16''1/4''

1/4''13/32''

13/32''

Conductor AWG #20 #23 #16 #13 #13Impedance, ohms 50 75 50 52 50Attenuation/100', dB

@50 MHz 3.3 2.4 2.5 1.3 1.3@110 MHz 4.9 3.4 3.7 1.9 1.9@1,000 MHz 21.5 12.0 13.5 8.0 8.0

Reprinted with permission from Boatowner’s Electrical Handbook, second edition, by Charlie Wing

Coaxial CablesTABLE

16-1

trademark held by Times Microwave Systems(www.timesmicrowave.com). This cable isgenerally considered superior to any of the R-designated cables. The company has a lot ofexperience developing special cable for mili-tary applications; LMR cable is one by-productof their research and development.

This discussion may seem cryptic, butthe electronic equipment manufacturersgenerally make the decision for us in termsof what cable to use. For example, AncorMarine (www.ancorproducts.com) makessome very specific recommendations in itscatalog: RG-58C/U for interconnectingelectronic equipment; RG-59/U for televi-sions and some satellite systems; RG-8X forVHF radios in which the distance from theantenna to the transceiver is less than 50feet; and RG-8/U for VHF with longer cableruns to the antenna.

The NMEA on Coaxial CableWhen all is said and done, however, the bestresource for sorting through all of this is theNMEA. It devotes ten pages of its electron-ics installation standard to coaxial cablerequirements—in standards writing, that’ssignificant. (But even the NMEA will tell

you to first consider the equipment manu-facturer’s recommendations.)

The NMEA defines maximum acceptablelevels of signal loss for different types of equip-ment, shown in Table 16-2. Use these valuesunless the equipment manufacturer specifies alower value.

Attenuation

Next let’s look at the specified attenuation forthe different cable types, as shown in Table 16-3.Specifications for attenuation in cable with thesame basic designator (various brands of RG-58or RG-8X, for example) may differ slightly fromone manufacturer to another. It is advisable todouble-check the values in the table againstthose for the specific brand of cable you areusing, particularly if you’re installing long cableruns. It could mean the difference between apass/fail situation for a given installation.

Impedance

Of course the last spec to match is the inher-ent impedance of the cable. Some applicationscall for 50-ohm cable, others 75-ohm cable.Impedance ratings of various cable types areshown in Table 16-4.


Equipment Maximum Loss (dB) Operating Frequency

VHF radio 3 162 MHzSSB radio 3 2—22 MHzCell phone 3 850 MHz or 1.9 GHzTelevision 6 54—806 MHzSatellite TV 6 1.6 GHzGPS 3 1.5 GHzDGPS 3 150—500 kHz

Source: NMEA

Maximum Allowable Signal Loss by Equipment Type (per NMEA)TABLE

16-2

Other 75-ohm cable sizes sometimes usedin marine applications are RG-6 and RG-11,but these are rather difficult to find in mostchandleries.

INSTALLING COAXIAL CABLE

When installing cable, be careful about mis-matches; that is, connecting two cablestogether that have different resistance values orconnecting cable with the wrong impedancevalue to a piece of equipment. The longer thecable run, the more this mismatch will affectthe performance of the equipment.


Cable Frequency (MHz)Size 30 50 100 1,000 2,400

RG-58A/U 2.5 4.1 5.3 24 38.9RG-59 —— 2.4 3.5 12 ——RG-8X 2.0 2.1 3.0 13.5 21.6RG-8/U —— 1.3 2.2 9.0 ——RG-213 1.2 1.6 1.9 8.0 13.7LMR-240 1.3 1.7 2.5 8.0 12.7LMR-400 0.7 0.9 1.3 4.1 6.6

Attenuation in dB per 100 Feet of Coaxial CableTABLE

16-3

Cable Lengths

The NMEA suggests that cable lengths bemodified for the specific installation. The coilsor bundles of coaxial cable that we so oftenfind hidden behind panels are not desirable orwise. Cut the cable to the length you need andinstall a matched cable end. Allow a minimum12-inch service loop at the equipment end.(This, of course, would only apply if theequipment manufacturer does not specificallyprohibit the alteration of the coaxial length,which, as discussed in Chapter 14, is often thecase.) The goal is to make the most direct con-nection possible in order to reduce the attenu-ation between the antenna and the device to aminimum.

In routing coaxial cable, pay attention toits minimum bend radius. Sharp bends incoaxial cable increase attenuation and con-tribute to signal loss in the run. Minimumradius bends for different cable types are spec-ified by the NMEA, but you should alwaysconfirm the cable manufacturer’s minimumbend specification for a type of cable, as thenumbers vary from one manufacturer toanother. Table 16-5 shows minimum bendradii per NMEA requirements.

Cable Size Impedance (ohms)

RG-59 75RG-58 50RG-8X 50RG-8/U 52RG-213 50LMR-240 50LMR-400 50

Inherent Impedance byCoaxial Type

TABLE

16-4


Minimum Bend Cable Type Radius (inches)RG-58/U 2.0RG-8X 2.4RG-8/U 4.5RG-213 5.0LMR-240 0.75LMR-400 1.0

Source: NMEA

Minimum Bend Radii ofCoaxial Cable, by Type

TABLE

16-5

Coax Connectors

In any circuit, the weakest link is generally at atermination point, and it’s no different forcoaxial cable. The specialized end connectorsused to install coax reflect the fact that it isreally a multiconductor cable and is designedto deliver signals of varying frequencies. Ourfriends at the NMEA provide some guidancehere as well. The maximum operating fre-quency and impedance for the various connec-tor types available are shown in Table 16-6.

Connector Maximum Operating Designator Frequency Impedance (ohms)UHF (PL-259) 300 MHz 50BNC 4.0 GHz 50TNC 2.5 GHz 50N 11.0 GHz 50F 2.0 GHz 75Mini UHF 2.5 GHz 50SMA 12.0 GHz 50SMB 4.0 GHz 50FME 200 MHz 50

Source: NMEA

Coaxial Connector SelectionTABLE

16-6

PL-258UHF double-female

M359UHF 90 male/female

UHF double-male

M-348UHF T-adapter

UHF female/BNC male

UHF male/ BNC female

A few coaxial adapters. (Reprinted with permission fromBoatowner’s Illustrated Electrical Handbook, second edition,by Charlie Wing)

1 7 1

As you can see in the table, the connectorimpedance must match the device’s operatingfrequency spectrum as well as the cable.Table 9-1 in Chapter 9 outlines the variousequipment operating frequencies.

Installing connectors requires specialcare—if done incorrectly, you can create ashort circuit between the center conductorand the shield. A quick Internet search willidentify a plethora of specialized stripping andcrimping tools available for the various coaxialcable types. They range in cost from $10 to $40,and are a good idea of you work with coax on aregular basis. Many veterans still prefer to stripthe outer jacket and center conductor insulationwith a pocketknife. That certainly works if youare careful, but I find the dedicated strippersquicker and more reliable (see sidebar page 173).Be aware when using a such a tool that the cut-ter blade orientation must be matched to thecorrect cable. Otherwise the tool can damageinsulation or the wire conductors.

The photo sequence that follows shows theprocedure for stripping cable using a specializedtool. It’s important to use a tool specificallydesigned for the coax you are working with,because the tool’s cutter spacing is designed tocarefully remove insulation without damagingthe conductors in the cable. (The cable strippershown is made by Ancor and strips coax labeledRG-58, RG-59, RG-8X, and RG-62.)

You have two choices when it comes toconnectors. One is the traditional solderedtype, which requires you to solder the centerconductor and shield to the center pin andouter case of the connector. The second type isthe solderless connector (shown in the pho-tos). Most technicians I know are movingaway from the soldered type, finding themvery labor intensive to install while offering noadditional performance over solderless con-nectors. In fact, some of the newest connectorseliminate the need for the stripping procedurealtogether, further simplifying this process.

coaxial cable and antennas

STEP 1: Slip on shell and strip to center of conductorand back 3/4"

STEP 2: Strip outer jacket additional 5/16"

STEP 3: Slip on body, making sure shield does not contactcenter conductor, and solder tip and shield through holes

STEP 4: Screw shell onto body

3/4"

3/4"

5/16"

STEP 1: Slip on shell and adapter;strip outer jacket back 5/8"

5/8"

STEP 2: Bend back braided shield

STEP 3: Slip adapter under braided shield

STEP 4: Strip center conductor 1/2" and tin

STEP 5: Screw on body and solder tip and braidthrough holes in body

STEP 6: Screw shell onto body

1/2"

ON RG-58/U, RG-59/U, AND RG-8X CABLES

ON RG-8/U AND RG-213 CABLES

Assembly of PL-259 (UHF) connectors. (Reprinted withpermission from Boatowner’s Illustrated ElectricalHandbook, second edition, by Charlie Wing)


13/64"

5/16"

5/16"

STEP 1: Cut cable end even andstrip outer jacket back 5/16"

STEP 2: Slide clamp nut and pressure sleeveover cable; straighten braid ends

STEP 3: Fold braid back; insert ferrule inside braid;cut dielectric back 13/64"; tin conductor

STEP 4: Trim excess braid; slide insulator over conductorinto ferrule; slide female contact over conductor and solder

STEP 5: Slide body over ferrule and press all partsinto body; screw in the nut tightly

STEP 1: Cut cable end even and stripouter jacket back 5/16"

STEP 2: Slide clamp nut and pressure sleeveover cable; straighten braid ends

STEP 3: Fold braid back; insert ferrule inside braid;cut dielecric back 13/64"; tin conductor

STEP 4: Trim excess braid; slide insulator over conductorinto ferrule; slide male contact over conductor and solder

STEP 5: Slide body over ferrule and press all partsinto body; screw in the nut tightly

ON RG-58/U, RG-59/U, AND RG-8X CABLESFEMALE CONNECTOR

MALE CONNECTOR

13/64"

Assembly of BNC connectors. (Reprinted with permissionfrom Boatowner’s Illustrated Electrical Handbook, secondedition, by Charlie Wing)

Insert the coax into the tool to the specified length.

Close the tool and rotate it 1/2 turn clockwise, then counter-clockwise, cutting through the outer insulation jacket.

Remove the cut outer jacket to expose the shield conductor.

Pull back the shield to expose the center conductor insulator.

1

2

3

4


#702050, Ancor Marine, www.ancorproducts.comCoax Stripmasters, Ideal Tool, www.idealindustries.comCST or LC CST series, Paladin Tools, www.paladin-tools.com

COAXIAL CABLE STRIPPERS

There are still many in the field who preferthe soldered approach but I’ve seen more ofthat type messed up than I have the appropri-ate solderless type. One argument for solder-ing is that they will be less prone to corrosion.I contend this is a moot point because whensealed as described below with 3M Scotch2228 tape, water will not get to the connector,eliminating the corrosion issue.

Once you’ve made the cable terminationand joined the male and female ends of theconnectors, it’s important to secure the con-nections. This is often done with Ty-wrapsequipped with screw mounting brackets torelieve any potential strain on the connection.If you’re installing the connection in a loca-tion exposed to weather, you will also need toseal it against water intrusion. There are sev-eral methods for waterproofing; here are two:

1 Heat-shrink tubing. This method entailsdealing with the disparity in the diametersof the coaxial cable connector and thecable itself. One way to do this is by slid-ing two to three 1/2-inch lengths of heat-shrink tubing (sized to accommodate thecable diameter) onto the coax beforeinstalling the connector male and femaleends. Once the cable ends are attached,shrink the lengths down onto each other,which effectively builds up the outsidediameter of the coaxial cable insulation.Then, when the connector is assembled(with a length of heat-shrink tubing sized

Use the smaller-diameter cutter on the other end of thetool to strip the center conductor insulation.

The stripping process is complete and the cable is readyfor the connector to be installed.

A gold-plated solderless connector made by Shake-speare (www.shakespeare-marine.com). Another popularmodel is available from Centerpin Technologies(www.centerpin.com). Gold plating greatly reduces atten-uation due to its superior conductivity.

5

6

to accommodate the connector barrellength plus about 3/4 inch on each end),the tubing will shrink down onto the pre-viously installed short lengths, effectivelysealing the entire assembly.

I don’t like this method because thematerial only shrinks so much for its nomi-nal size, and sometimes it’s not enough toaccommodate the difference in diametersbetween the cable and the connector.

2 Tape wrap using 3M Scotch 2228 RubberMastic Tape (my preference). This mate-rial seals tenaciously to itself as it’s over-lapped, and once in place, it is incrediblydifficult to remove. In fact, a razor knife isalways needed to cut it off the connectionwhen it’s time for service.

Calculating Loss

To ensure that the run from the antenna ortransducer to your piece of equipment iswithin the tolerance specified in Table 16-2,you will need to conduct a simple loss calcula-tion. This is an important step of any coaxialcable design/installation procedure.

To perform this calculation, simply addthe attenuation through the connectors to theattenuation from the coaxial cable. TheNMEA uses a constant of 0.5 dB to indicatethe loss per connector for this calculation. Youwill also need to count the number of connec-tions, and remember that inherent loss per100 feet of cable run is based on the frequency.

Let’s try an example using RG-8X cable toconnect a VHF radio with its antenna. Theradio’s operating frequency is 162 MHz, whichwe’ll round off to 160 MHz, and the cable runis 50 feet. Based on the specifications for RG-8X cable, the signal loss per 100 feet is 4.0 dB@ 160 MHz. The math looks like this:

(L � 100)4 dB � TCL

where L � length, and TCL � total cable loss


Plugging in the numbers above, we findthat the total cable loss is:

(50 � 100)4 dB � 2

Then we add the loss from the two connec-tors (0.5 dB each), for a total loss of 3 dB. Sincethe maximum loss allowed by the NMEA is3 dB for a VHF system (per Table 16-2), we’re in!

VHF ANTENNAS

Like coaxial cable, antennas also greatly influ-ence equipment performance. If the wrongchoices are made in antenna selection orinstallation, serious problems will result.

For most boaters, their VHF radio is theall-important link to the U.S. Coast Guard ifan emergency arises, so maximum radio rangeis an important safety consideration. Sincethe FCC limits power output from aninstalled VHF transceiver to 25 watts, theantenna installation is the key to maximizingeffectiveness.

That said, many radios rated at 25 wattsactually transmit at 20 or 21 watts. Lower out-put translates into less range at the antenna, so itis important to test for VHF power output toensure peak transmission range. Higher-quality,name-brand radios tend to be very accurate. Toperform the test, use a power standing waveratio (SWR) meter, as outlined below:

1 Connect the meter to the VHF radio’santenna jack.

2 Plug a dummy load into the meter’santenna jack.

3 Key the transmit button on the micro-phone to take a direct reading of theradio’s transmit power.

4 Read the wattage output on the meter’sgauge. Don’t be surprised if a 25-watt radioonly reads 18 or 19 watts of actual output.

We’ll return to SWR meters shortly.

Antenna Gain

Antenna gain is a measure of an antenna’seffectiveness. It has to do with the radiatedpower of the antenna, but it isn’t about theantenna generating power; it’s about how theantenna concentrates the electromagneticenergy—the radio frequency—received fromthe radio. Gain is measured in decibels just likethe loss factor we discussed earlier. The gainof the antenna, as well as its length, determinesthe radiated pattern emitted from the antenna.As the dB rating increases, the transmittingpower is compressed into a progressively nar-rower beam, making the signal go farther, butalso making its direction more critical for suc-cessful reception at the other end.

You can increase the radiated power from theVHF radio by installing an antenna with ahigher gain rating, although it doesn’t alwaysimprove performance in real-world conditions.A 9 dB rated antenna transmits farther, but itsbeam is narrower, so if it is mounted at the mast-head of a sailboat and the sailboat is heeled, thesignal would be angling up into the sky on oneside of the boat and down into the water on theother. For sailboats, therefore, a 3 dB antenna is amore desirable choice. Even though the radiated


Test rig for checking VHF power output. The connector on the left plugs into the antenna jack on the radio set, while thedummy load on the right takes the place of the antenna. (Note: Never bend coaxial cable as far as shown here. The cablewas bent far beyond its specified minimum radius and held in place with a cable tie only for the purposes of the photo.)

no gain (handheld6–10" antenna)

VHF-FMantenna

9 db 6 db3 db

beam doesn’t extend as far as the 9 db beam,it’s more likely to reach a receiving station.Powerboats, on the other hand, are inclined torun in a more level position, and they can use6 dB or 9 dB antennas more effectively, althoughas a boat rolls in beam seas, transmissions maystill fade in and out.

Typical radiation patterns of VHF-FM radio antennas.A 9 dB gain antenna, which might be 24 feet long, offersgreater potential range but also a vertically compressedsignal. When the boat rolls, you might be transmittingdown into the sea on one side of the boat and up intospace on the other side. Many powerboaters choosea 6 dB, 8-foot antenna as a good compromise.(Reprinted with permission from Boating Skills andSeamanship by the U.S. Coast Guard Auxiliary)

Standing Wave Ratio

The standing wave ratio (SWR), which is theratio of the maximum RF current to the mini-mum RF current on the line, can be thoughtof as a measure of an antenna system’s effi-ciency. (By system, I mean the antenna plus thecoaxial cable between the antenna and thetransceiver.) The smaller the ratio, the moreefficient the system, so an antenna system withan SWR of 1:1 is experiencing less loss thanone with a 3:1 SWR. Antenna design can havea profound effect on the SWR. By integratingvarious choke methods into the antenna, man-ufacturers can contain more RF power in theantenna element, as opposed to allowing it toleak back into the cable. You can think of thechoke as a one-way valve designed to separateyour antenna from the feed line, thus deliver-ing all the power to the antenna for maximumpower and directional control of the transmit-ted signal. Amateur radio operators call thesechokes “baluns,” for balanced/unbalanced, as


they balance the signal between the antennaand the cable.

To test the SWR ratio of a system, weagain use the power standing wave ratio metershown in the photo on page 175. The steps areas follows:

1 Install the meter in series between theradio transceiver and the coaxial cablerouted to the antenna.

2 With the meter switched to the SWRfunction, key the radio microphone andobserve the meter’s reading.

3 Use the graph on the back of the meter toconvert your reading based on the wattageoutput you measured (see page 174).

Align your SWR reading on the X-axisand with the Y-axis wattage reading tofind the corrected SWR value.

An acceptable SWR is a matter of opinion.Some say that 3:1 is OK; others use a 1.5:1ratio as their maximum. A value of 2:1 equalsabout a 90% efficiency level, and this is quitegood. A 3:1 ratio represents about 75% effi-ciency, which, in my opinion, is a barely pass-ing grade. A quality installation will give you acorrected reading between 1.2 and 1.6.

My Micronta (RadioShack) SWR/powermeter (shown in the photos) is a long-discontinued model. Similar inexpensivemeters, such as the ART-2 from Shakespeare,are available for about $50 through Boater’sWorld stores (www.boatersworld.com). Aworthwhile step up for some readers mightbe one similar to the Vectronics model listedin the sidebar, available from RadioShack forabout $230. Some electronics specialistsmight benefit from a high-end unit, such asthe one from Bird Electronic; however, atprices ranging from $1,200 to $1,500, theseare not worth it even for advanced-levelboaters.The conversion graph on the back of the meter.

When considering an SWR meter, payattention to its frequency range. For VHF use,it must able to operate in the 162 MHz fre-quency range. (Not all SWR meters dobecause most are used by CB and ham radiooperators who only need a frequency range upto about 30 MHz.) The Vectronics unit has arange from 1.8 MHz to 170 MHz, and thefrequency-operating range on my ancientMicronta unit is 144 MHz to 440 MHz.

SSB ANTENNAS

SSB antennas are key to the effectiveness ofSSB radios—perhaps more so than with otherradio installations—because the goal is verylong range communication capability. Ratherthan being concerned with a 20- or 25-milerange, here we’re thinking in terms of hun-dreds, and even thousands of miles! They arealso more complicated, since an SSB antennasystem has two parts: the abovedeck part, andthe belowdeck (generally in the bilge) counter-poise part (see below). There are three types ofSSB antennas commonly used on boats:

1 Vertically mounted whip antennas are com-mon in most powerboat installations.

2 Wire (or whip) antennas are common onsailboats. The standing rigging (mostoften the backstay) makes up part of theantenna.

3 Halyard antennas are a new style catchingon among some cruising sailors. Here theantenna is a rope halyard with a wire core of

a specific length. They are reportedly quiteeffective and can be raised and lowered easilywhen not in use.

The Counterpoise

The counterpoise, also called a ground plane, is aconductor or system of conductors used as asubstitute for earth or ground in an antennasystem. It is unique to wire or whip antennasand is a necessary component for the antennato be effective. It allows the antenna to “see” animage of itself; i.e., to effectively reflect andtransmit the radio signal. If the radiating por-tion of the SSB antenna system doesn’t see itsreflection, it simply won’t work. Consider thecounterpoise the second part of the antennasystem. An inadequate counterpoise will mostoften manifest as poor range reception for theradio, especially at lower frequencies.

There are several ways to create a counter-poise:

• Use the hull of a metal boat. • Add metal to the hull of wooden or fiber-

glass boats.• Install a copper screen on the inside of a

nonmetallic hull with a resin overlay tokeep it in place.

• Tie into a ground plate that is in contactwith the water.

• Use flat copper foil “tape” and attach it tometal through-hull fittings. (According tothe NMEA, the tape should be at least2 inches wide, but some manufacturers,


ART-2, Shakespeare, www.shakespeare-marine.comSWR-584B, Vectronics, www.vectronics.comAT-400, Bird Electronic, www.bird-electronic.com

SWR METERS

including ICOM, specify a minimumwidth of 3 inches.)

Because copper foil is the most commonmethod for creating a counterpoise, we’ll dis-cuss that method in more detail.

Creating a Counterpoise withCopper Foil TapeFirst let’s go over a bit of background. We usefoil instead of insulated copper conductorsbecause radio frequencies do not travel throughconductors—they travel on the surface of con-ductors. This phenomenon is sometimesreferred to as the skin effect, and the greater thesurface area, the better. One hundred squarefeet is often recommended as the minimumsurface area for an effective ground plane. Thatnumber may seem high, but you can achieve itrather easily by tying in various bits of metal onthe boat with the copper foil tape. Goodchoices include metal through-hull fittings,

metal water tanks, and encapsulated lead keels.The best pieces of metal are those that arelocated below the waterline because they willachieve an effective capacitive counterpoise tothe seawater; that is, without necessarily havinga direct connection to the seawater.

Warning: Never use a metal fuel tank aspart of the counterpoise—you will create anexplosive hazard!

To connect copper tape to a metal hull, youneed an isolating connector. Use series 316stainless steel contact points (these can be madeup of 316 stainless nuts, bolts, and washers, allreadily available at any chandlery), and seal theconnection with a water-excluding product likeBoeshield T-9 (www.boeshield.com) or Corro-sion Block (www.nocorrosion.com).

If your boat is wired to ABYC electricalspecifications, then the through-hull fittings willalready be bonded via a green wire conductor.If so, you can route the copper tape to the


copper foil

backing plate forbelow-waterlineground plate

Copper tape is used to connect the SSB radio antenna to the ground plane or counterpoise. On thisboat the tape is connected to a ground plate below the waterline. The metal plate shown is actually thebacking plate for the Dynaplate ground plane, which is mounted outside the hull, below the waterline.Dynaplates are “sponges” made of sintered bronze. When viewed under high magnification, this mate-rial appears as a series of connected small spheres. It is extremely porous and thus exposes far moremetal surface area to the water than its physical dimensions suggest.


waterlinecopper screen

bonded through-hull fitting (seacocks shown)

antenna

copper ribbon “tape”

waterline

bus bar

SSB radio transceivermetal water tankantenna tuner

ground

Installation of SSB radio, antenna, and counterpoise.

GND ANT GND IN ANT

Backstayinsulator

Antennatuner

Insulatedlead

Terminal

7-footclearanceminimum

SSB radio

3-inch copper foil

B

A

A

B

C

C

GROUNDING IN ORDER OF EFFECTIVENESS:

Encapsulated metal keel

Largest sintered groundplate

100 sq. ft. of copper or bronzescreening glassed to inside ofhull below waterline

SSB antenna and ground connections. (Reprinted with permission from Boatowner’s Illustrated Electrical Handbook,second edition, by Charlie Wing)


Stainless 3 dBwhip (VHF)

Stainless whip (VHF)

Fiberglass 6 dBwhip (VHF) or23' SSB

Insulated backstay (SSB)

Backstay insulator

Insulated mizzen stay (SSB)

Radar

Radar

Fiberglass 6 or 9 dB whip (VHF)

Stainless 3 dB whip (VHF)

GPS

Radar

GPS

Locating antennas. (Reprinted with permission from Boatowner’s Illustrated Electrical Handbook, second edition,by Charlie Wing)

1 8 1

bonded fittings, securing them with a hoseclamp or other suitable mechanical fastener,such as a stainless steel bolt and washer (if thefitting has a drilled and tapped hole).

Caution: When tying in the copper tape,avoid creating a likely scenario for galvaniccorrosion (see Chapter 11). For example, neverattach copper tape to an unbonded through-hull fitting. If any of the other through-hulls arebonded (as they should be), the fittings will havedifferent ground potentials. Also, never connectcopper tape directly to an aluminum or steelhull. The dissimilarity between the two differentmetals will create a focal point for galvanic cor-rosion. Remember, all that is needed to inducecurrent flow is a difference in potential from onepoint to another and an electrolyte.

As you look for places to tie in, keep in mindthat the counterpoise will be most effective if itis located directly below the antenna or the

coaxial cable and antennas

terminal

backstayinsulator

insulatedlead

The lower (left) and upper (right) connections for a backstay antenna. The insulator blocks are connected to the rod-typerigging with swageless fittings. A rigger needs to splice in these insulators at both ends. Depending on the boat’s riggingtype, there are various methods of splicing these insulators. Two older methods included simple ceramic insulators, with thewire rope of the stay looped through a thimble and nicopressed in place; and swaged end fittings used with cotter pins.

insulator

back-stay

VHFantenna

cellphone

antennaSSBwhip

antenna

loranantennas

A typical powerboat whip antenna is shown far right.These need to be at least 23 feet long. The wire lead fromthe antenna tuner to the attachment point on the antennacounts as part of the antenna’s total length.

automatic antenna tuner (if one is installed), asshown in the top illustration on page 179.

Antenna Installation

As mentioned above, the two most common SSBantenna configurations are the extended whipantenna and using the standing rigging on a sail-boat (see illustrations page 180). For a whipinstallation, the antenna needs to be at least 23feet long; for a standing rigging installation, theantenna is typically 30 to 70 feet long, dependingon the size of the boat (see photos page 181).

This variation in length may seem to con-tradict the precision of the SSB system andantennas in general, but by adding an auto-matic tuner at the base of the antenna (com-mon on most modern boats), the effectivelength is automatically adjusted for the fre-quencies used in SSB operation. On those rareinstallations without automatic (or even man-ual) tuners, the length of the antenna must becarefully determined based on the frequenciesthe operator wishes to use. In reality, this is animpractical solution for any boat installation.

Safety Issues

Safety is an important consideration as youplan your SSB antenna installation. Passengersand crew must be protected against live wiresand high voltage. Keep in mind that whenthe SSB is in Transmit mode, the voltagedelivered to the base of the antenna systemcan be on the order of 5,000 volts!

Particularly with a backstay antenna, youmust design the installation so that no one canreach or touch the wire accidentally during atransmission (whip antennas are typically wellout of the way). At the base of the backstayrig, the height needs to be at several feet abovearm’s length when standing (as shown in thephoto on page 185).

It really isn’t a problem on the split-backstayboat shown in the photo because the connectionpoint for the antenna is at the peak of the triangle,


well above the deck. On single-backstay rigs, youcan achieve adequate protection by placing Teflontubing over the stay, again to a height beyondarm’s reach while standing.

The cable feed to the attachment point ismounted on insulated standoffs up the rig to thepoint where it turns into the antenna, as shownin the photo. The cable of choice for this purposeis GTO-15, which is actually ignition wire, andits insulating properties are in the 15,000 Vrange. Never use coaxial cable for this purposebecause its insulation properties are inadequate.At the upper end of this rigged antenna, positionthe insulator to maintain at least 3 feet of clear-ance between the live wire section and the mast.

The cost and involved procedure forinstalling an SSB antenna in standing rigging isoften one reason boatowners choose extendedwhip antennas for their sailboats. Whip antennasare much simpler to install. All you have to do isassemble the whip and mount it clear of otherantennas by at least 4 to 10 feet (depending onthe uses of the other antennas; see Table 16-9).

In summary, the considerations for SSBantenna installation are:

• Antenna length (23 feet minimum for awhip antenna; 30 feet minimum for astanding rigging antenna).

• The antenna counterpoise is critical to therange of the transceiver (more is better).

• Flat copper foil tape is the conductor ofchoice to connect the counterpoise.

• Position the antenna tuner and coun-terpoise as close to the base of theantenna as possible for maximumeffectiveness.

• Use only GTO-type cable for the connec-tion between the antenna and the tuner.

• On sailboat installations, make surethat crew and passengers can’t touchthe active part of the antenna duringtransmission.

• All electrical connections need to be firstclass, and insulated from weather withself-sealing tape or heat-shrink tubing.

SATELLITE TELEVISION ANDRADIO ANTENNAS

We looked at some of the issues concerningGPS and DGPS antennas in Chapter 14, butwe haven’t yet addressed the seemingly inert tele-vision disc antennas used on many boats.These, like most of the antennas we’ve dis-cussed, use coaxial cable to connect to the backof the television, so all the RFI and coiling rec-ommendations apply here as well. These anten-nas typically come with 30 feet of coaxial cableattached that can be extended if necessary, aslong as the loss factors are kept to a minimum.

Many disc-type television antennas alsohave amplification circuitry built into them toenhance reception. This circuitry requires sep-arate DC (positive and negative) wiring and,as with all DC wiring, voltage drop should bekept to a minimum. But since this is not acritical device, a 10% voltage drop would beacceptable under ABYC standards.

You might assume that these are receive-only devices that may pick up interferencefrom radios transmitting at frequencies closeto the VHF, UHF, or FM bands. However, afew years ago the U.S. Coast Guard deter-mined that some TV antennas can interferewith GPS antenna reception, causing inaccu-racies in GPS positioning or even blinkingout. Reports to the Coast Guard indicate thatGPS on vessels as far as 2,000 feet from anactive TV antenna have been affected. On theother hand, I’ve heard of cases in which inter-ference problems were solved by increasingseparation by a mere 12 to 18 inches.

The FCC identified three specific antennamodels in a safety bulletin issued December30, 2002 (TDP Electronics [i.e., Tandy Cor-poration] models 5MS740, 5MS750, and

5MS921), but stated that the problem maynot be exclusive to these three. Similar prob-lems were found in RadioShack model 15-1624and Shakespeare SeaWatch model 2040 withcode dates of 02A00 and 03A00.

The best way to check for a problem betweenthe TV and GPS on your boat is to first turn onboth the TV and the GPS, then shut down theTV while watching the GPS to see if any changesoccur with the GPS reading or display.

Little information is available from vendorsregarding mounting location, although onevendor suggests that the TV antenna be mountedas high as possible, and above all other onboardantennas. This makes sense, but it may not befeasible in many cases—for example, on a sport-fishing boat with a 30-foot SSB whip antenna.You may have to resort to the trial-and-errorapproach, experimenting with different loca-tions for the TV and GPS antennas beforemaking the installation permanent.

As of this writing, satellite radio representsone of the hottest accessories on the market.Most satellite radio antenna vendors provide a12-foot length of coaxial cable, although thislength is not crucial. And these antennas do notappear to be too sensitive as to where you locatethem. As long as they have about a 90-degreeclear view of the sky as measured from the cen-ter of the antenna dome (i.e., a 45-degree arcfrom the vertical centerline), all will be well.

CELL PHONE ANTENNAS

Most people jump on their boat and cast offwithout giving their cell phone’s ability to makeor receive calls a second thought. This generallyworks out because, in most cases, the body ofwater these people are on is actually never toofar from a cell tower. But suppose you are20 miles offshore doing a coastal delivery oranchored out at an offshore fishing ground, andyou want to use your cell phone. Odds are itwon’t work when you’re standing on a deck 1 or


2 feet above sea level with a 3-inch antennaextended out of your flip phone.

Like VHF radio and radar, cell phones area line-of-sight system. So if we add a remotecell phone antenna, we can “stretch” the hori-zon out as far as possible. Like VHF antennas,these are available with different gain ratings,typically 3 dB and 9 db.

At least two companies—Shakespeare(www.shakespeare-marine.com) and DigitalAntenna (www.digitalantenna.com)—makecombined VHF and cellular antennas. A devicesplitter on the equipment end of the coaxialcable allows both systems to be attached, but ofcourse they cannot be operated simultaneously.

The compromises already discussed in theVHF section of this chapter apply here. A3 dB antenna generally works better at themasthead on a sailboat due to its wider beam,which helps offset the effects of the boat’sheeled position. A 9 dB antenna has a longer,narrower beam. One compromise that workson both powerboats and sailboats is the use ofan 8- or 9-foot whip, mounted on an exten-sion pole set on a stern rail or on a dedicatedantenna-mounting system. The antenna leadis usually terminated with a mini BNC-typeplug that inserts directly into the back of thecell phone. (The socket is often hidden undera cap; you may need to pry it out.)

RADAR ANTENNAS

The most important consideration for a radarantenna or scanner—besides its output ratingand whether or not it is an open or closed array(dome)—is its position on the boat. Focusingthe antenna’s powerful emitted beam is impor-tant to the accuracy and detail of the returnedsignal. The power output from the antenna orscanner is a guide to the expected range of theunit—more power means more range. Mostradar antennas used on recreational boats haveoutputs in the 2 kW to 10 kW range, and

these are matched by the manufacturers totheir respective display units. (Not all antennasare compatible with all display units, eventhose from the same manufacturer.)

These are powerful devices and safety mustbe an important consideration:

• Scanners have high-voltage componentsand connections within their housings.These units should only be serviced oradjusted by factory-trained technicians.

• Radar antennas transmit high-level electro-magnetic energy that is dangerous tohumans. They should always be mountedabove head height or well below it, depend-ing upon the boat configuration. On a sail-boat, this is not a problem as the radarantenna is mounted either on a raisedmounting pole far aft or well up the mast.It is sometimes a problem on a powerboatas the antenna sometimes gets mountedforward of a flybridge deck directly in frontof the operator at the upper helm station.This configuration should be avoided!

• Never look directly at a scanner when it isoperating, and keep people out of theemitted-beam path, which covers a full360 degrees.

• There are strict international regulationsthat cover radar and its emissions. Someunits that are available in the UnitedStates do not comply with EuropeanUnion regulations, and may not be usedthere. The manufacturers usually makethis information readily available. In theUnited States, the FCC regulates radaruse; in Canada, it is regulated under theCanadian Shipping Act. As of this writ-ing, efforts are underway to integrateCanadian and U.S. requirements.

Like VHF radio, radar is a line-of-sightdevice, so a higher scanner mount will give theunit greater potential range. But as with VHF,


too high can be a problem for radar, as the boat’srolling and pitching is amplified at a masthead,for example. A compromise is therefore in order.The NMEA recommends a minimum height of8 feet abovedeck, and a maximum height abovethe waterline of 30 feet. Keep in mind that largeobjects in the same horizontal plane as the radarbeam will interfere with its signal and may causeblind spots or false targets to appear on the radardisplay.

On many sailboats, the radar scanner ismounted high on the leading edge of themast, which may cause a blind spot on theradar screen directly aft of the boat. One wayto minimize this effect is to mount a woodenblock between the back of the radome and themast, as wood is less reflective to the radarbeam and will be less likely to create anobscure target on the radar screen.

On powerboats, the concern is the fore-and-aft trim angle of the boat. If you have a planing-hull powerboat, you can fabricate a wedge orbracket to adjust the antenna’s plane angle toaccommodate the rise of the bow when the boatis on plane (see illustrations next page). For own-ers of displacement-hull powerboats, this is notmuch of a problem since they don’t experienceas much bow rise underway as planing hulls.

Radar scanners are available in differentpower configurations. Typical small-boat unitsare available in the 2 kW to 5 kW power range.Larger craft often use units with power ratingsup to 10 kW. Higher-output units work better infog and rain, which is generally when a radar ismost needed, because fog and mist absorb someof the radiated energy from the antenna, effec-tively reducing the potential range of the unit.

But radar is a line-of-sight system in boththe Transmit and Receive modes. So moreimportant than transmitting power to the sys-tem’s range capability are the relative heightsof the radar antenna on your boat and the tar-get in the distance; tall is good, short is harderto see. It’s worthwhile to question whether you


satellitedome

GPS

GPSdifferentialantenna

radome

mountingpole

insulatedstandoffs

split backstay

An effective radar mount on a sailboat. It is up out of theway of crew, elevated enough to provide an acceptableline-of-sight range, and far enough behind the mast so thatthe mast will interfere only minimally with its line of sight.Some mounts of this type articulate automatically from sideto side, leveling the antenna to compensate for the boat’sheeling angle. (This photo also shows the split-backstaySSB antenna installation discussed on page 182.)

really need a radar with a 50-mile range,which the vast majority of boaters never use.As a boater, I’m more concerned with seeingtargets as they get closer to me so that I canavoid hitting them! Rather than impressingpeople with a 10 kW, 50-mile radar, I’d rather

have a unit with adjustable intrusion alarmfeatures and MARPA (mini automatic radarplotting aid) capabilities. And for the averageboater, a 4 kW unit will do the job nicely.

Although radar is a line-of-sight system,its range is actually a bit farther than that.Because atmospheric refraction bends thebeam slightly, a radar can actually “see” about15% farther than a human observer locatedat the same height. The location of theantenna on the boat (mounting it higherextends the horizon), the height of the target,and the visible horizon all make a difference.The height of targets located beyond thevisual horizon determines the actual radarrange. This distance (see Table 16-7) can becalculated as follows:

D H H= +( )1 144 1 2.


waterline

12.5˚

12.5˚

wedge orwashers

forward

using shims to lower the main beam

When mounting a radar antenna on a powerboat, ensure that the 25-degree vertical beam is leveled horizontally andnot obstructed by structures on the boat itself. Adjustable brackets and shim kits are available from radar suppliers asaids in leveling the unit (inset).

tiltedradome

A proper radar installation on a 35-foot lobster boat. Notice the slightdownward tilt to the radome relative to the cabin top. When the boat isrunning and its bow rises, this radome will be level, or parallel to thewater’s surface, which is the goal.

where D � distance in nautical miles,H1 � height in feet of the antenna, and

H2 � height of the distant object

Increase this distance by 15% for theabsolute maximum radar range.

While the height of the radome has anobvious effect on maximum range, it affectsminimum range as well. The radiated beamfrom the radar transmitter extends in a verticalarc 12.5 degrees above and below the horizon-tal centerline. The area below the lower half ofthe beam is a radar blind spot, or blind zone,and the higher the antenna is mounted, the

farther out this blind spot will extend (seeTable 16-8). The near distance can be calcu-lated from:

N1 � H1 � tangent 20° � 2.75 � (H1 � H0)

For example, a 40-foot-high antenna can-not see surface objects closer than 110 feet.Reducing the antenna height to 20 feetreduces the blind zone radius to 55 feet. Onmost boats, practical mounting locations arefairly limited, however, so the near blind spotmay be relatively fixed. That said, I feel thatradomes mounted on purpose-built articulat-ing pole mounts, like the one shown in the


Radar Height Target Height (H2, ft.)(H1, ft.) 5 10 20 40 60 80 100 200 400

5 5 6 8 10 12 13 14 19 2610 6 7 9 11 13 14 15 20 2715 7 8 10 12 14 15 16 21 2820 8 9 11 13 14 16 17 22 2925 9 10 11 13 15 16 18 22 2930 9 10 12 14 16 17 18 23 3040 10 11 13 15 17 18 19 24 3150 11 12 14 16 17 19 20 25 32

Reprinted with permission from Boatowner’s Illustrated Electrical Handbook, second edition, by Charlie Wing

Radar Line-of-Sight Range in Nautical MilesTABLE

16-7

D1

H1

N1 H0

±20°D2

H2

Radar range and blind zone versus heights of the antenna and the target. (Reprinted with permission from Boatowner’s IllustratedElectrical Handbook, second edition, by Charlie Wing)


Radar Height Target Height (H0, ft.)(H1, ft.) 0 1 2 3 5 10 15 20 30

5 14 11 8 5 —— —— —— —— ——10 27 25 22 19 14 —— —— —— ——15 41 38 36 33 27 14 —— —— ——20 55 52 49 47 41 27 14 —— ——25 69 66 63 60 55 41 27 14 ——30 82 80 77 74 69 55 41 27 ——40 110 107 104 102 96 82 69 55 2750 137 135 132 129 124 110 96 82 55


Radar Near Range (Blind Zone), N1, in FeetTABLE

16-8

Satellite VHF GPS SSB Radar (4 kW) Communications Cell Phone Satellite TV

VHF 4 3 3 2 6 2 3

GPS 3 0.5 4 vertical separation; 6 (and vertical 5 2GPS out of radar separation; GPSbeam below satcom)

SSB 3 4 10 3 6 2 4

Radar 2 vertical 2 1.5 vertical 6 cell out of 4 (more for(4 kW) separation; separation radar beam higher-power

GPS out radar)of radarbeam

Satellite 6 6 (and 6 6 6 6 6Commu- GPS nications below

satcom)

Cell 2 5 2 cell out of 6 3 4Phone radar beam

Satellite 3 3 4 4 (more for higher- 6 4 4TV power radar)

Source: NMEA

Recommended Horizontal Antenna Spacing (in feet, with vertical spacing whererequired)

TABLE

16-9


photo on page 185, offer the best compromisebetween serviceability, close range, and long-distance capabilities.

With so many different kinds of antennas onboard, it is almost inevitable that issues ofinterference will occur. However, by closelyfollowing manufacturers’ recommendations

concerning antenna location relative to othertransmitting and receiving antennas, you canmitigate most of these issues.

Table 16-9 summarizes the recommenda-tions of various manufacturers, but youshould refer to each product’s documentationfor the final say.

Onboard Networks

The marine industry is going through perhaps the most significant change in thirtyyears regarding onboard systems. Boaters are beginning to embrace what has beencommonplace in our working lives for some time now—the networking of electri-

cal and electronic components—with the result that sending data from one part of the boatto another is becoming mainstream. Many systems or methods, each with their ownstrengths and weaknesses, are vying for market share and technical acceptance. Vast changeswill occur in boat wiring in the near future; changes that may, to a large extent, do awaywith wiring altogether. Wireless systems are even being installed on a few very high endboats today, although widespread market penetration is, I believe, still several years away.

How will boatowners and marine electricians deal with all of this? What skills will beneeded to remain effective and relevant in servicing and installing these systems? These arethe questions I’ll address in this chapter. To facilitate our networking discussion, see thesidebar opposite on networking terminology, which includes the terms introduced inChapter 14.

NETWORK TYPES

Networking is not new to boats; the NMEA 0180 network standard—the first communica-tions standard created for the marine industry—has been around since 1980, and was fol-lowed shortly by the 0181 standard, and then 0183, which became widely accepted and wasthe mainstay for nearly twenty years. NMEA standards are accepted as the common practicefor how to share specific data information between competing entities or companies.

But over the years we’ve become so used to having nearly unlimited amounts of infor-mation at our fingertips at all times and in all places that advancements in this area wereall but inevitable. Today, networks and proprietary systems are all the buzz. Some usetwisted-pair harnesses to eliminate the effects of EMI; others use shielded wire sets. Butthe field problems related to networking go far beyond a difference in cable types. Issuessuch as data transfer rates, the types of data, plug connector compatibility, the number ofdevices that can be connected to the network, and the compatibility of equipment fromone vendor to another are concerns as well.

Let’s look at several networks to get a feel for what’s available and how they work.

Furuno NavNet

Furuno’s NavNet system is an Ethernet-based network, specifically a 10Base-T system.Ethernet protocol is available in several configurations that allow for varying amounts ofdata to be transmitted. 10Base-T is based on an IEEE standard protocol for identifying sys-tem features. In this case, “10” simply refers to the data transmission speed in megabits (Mb)

C H A P T E R

1 7


1 9 1onboard networks

COMPUTER AND NETWORKING TERMINOLOGY

In this discussion of networks, we will be entering what may be for some a new realm of specializedknowledge. To assist you, here are definitions for some of the terms used in this book:

bandwidth: A range within a band of frequencies or wavelengths. Also, the amount of data that canbe transmitted in a fixed amount of time; the data rate supported by a network connection or interface.Commonly expressed in bits per second (bps).

baseband: The original band of frequencies of a signal before it is modulated for transmission at ahigher frequency. Typically used to refer to the digital side of a circuit when the other side isbroadband or frequency based, meaning the signal is modulated. For example, in a cell phone, “RFto baseband” means pulling out the analog or digital data from the modulated RF signal receivedfrom the cell phone tower and converting it to pulses for digital processing.

black box: A sealed, unserviceable electronic control box that serves various functions within an elec-tronic or networked system.

broadband: In general, broadband refers to telecommunication in which a wide band offrequencies is available to transmit information.

CAN (controller area network): A serial bus network of microcontrollers that connects devices, sen-sors, and actuators in a system or subsystem for real-time control applications. There is no addressingscheme used, as in the sense of conventional addressing in networks (such as Ethernet). Rather,messages are broadcast to all the nodes in the network using an identifier unique to the network.Based on the identifier, the individual nodes decide whether or not to process the message and alsodetermine the priority of the message in terms of competition for bus access. This method allows foruninterrupted transmission when a collision is detected, unlike Ethernets that will stop transmission uponcollision detection. Controller area networks can be used as an embedded communication system formicrocontrollers as well as an open communication system for intelligent devices.

Ethernet: Originally developed by Xerox in 1976, it now describes a diverse family of frame-basedcomputer networking technologies for local area networks (LANs). It is the basis for IEEE standard802.3. (If you want to learn more about Ethernet protocol, the Internet is absolutely loaded with sitesthat will walk you through the various protocols and the cryptic codes that identify them.)

multiplexer: A communications device (black box) that combines several signals for transmission overa single medium.

network: A group of two or more computer systems linked together to share information andhardware.

network architecture: The structure of a communications network. An open architecture allows adding,upgrading, and swapping of components. It can be connected easily to devices and programs madeby other manufacturers. It uses off-the-shelf components and conforms to approved standards. Aclosed architecture has a proprietary design, making it difficult to connect the system to other systems.The hardware manufacturer chooses the components, and they are generally not upgradable.

protocol: In the context of data communication, a common set of rules, signals, and data structures(for either hardware or software) that governs how computers and other network devices exchangeinformation over a network.

sentence structure: In NMEA parlance, describes the sequence and type of data information codes thatare distributed throughout the network. (For specific sentence codes, see the sidebar on page 151.)

per second. “Base” describes the transmissiontype (in this case, baseband as opposed tobroadband). The “T” describes the wire type(in this case, unshielded twisted-pair cables).(In contrast, the protocol also describes a10Base-F system that utilizes fiber optics as thetransmission medium.)

The NavNet system uses proprietary lan-guage protocols and is only compatible withFuruno products, so mixing and matchingamong vendors to create an onboard systemwill be challenging. Some Furuno products arealso at least partially NMEA 0183 compatible,which will allow for some interfacing of non-Furuno products, but this interface capabilityis limited. The NavNet system is essentially aclosed, proprietary system.

Xantrex Xanbus

The Xanbus network system, developed byXantrex Technology, is a proprietary system. Itis based on CAN bus, and is compatible withNMEA 2000. It uses standard computer-typeCat 5 cabling to connect its various compo-nents and readily available RJ-45 terminal con-nectors, familiar to anyone who has workedaround computers or office networks. Whilethis system uses some NMEA 2000 languagefor data communications, it does not useNMEA 2000 proprietary cabling to connect itsvarious components. So again, we see thatnothing in this system is really standardized toallow simple integration of components fromdifferent vendors.

Mercury SmartCraft

SmartCraft is based on CAN technology tointegrate its electronically controlled engineproducts with other onboard systems such asengine monitoring instruments, generatorremote-start panels, and the like. Since CANhas been used in automotive applications sincethe late 1980s, this was a logical move for

Mercury because its applications are centeredon automotive-based engines that have beenmarinized, and the automotive market is cer-tainly much larger than the marine market,with lots of experience in the utilization ofCAN in car and truck applications. So in thiscase, the logic was to go with a proven technol-ogy. Again, mixing and matching SmartCraftequipment with other networking protocols isnot easily accomplished.

Raymarine SeaTalk

Raymarine uses its own proprietary SeaTalknetwork system, which can transfer data at100 Mb per second. There have been manyiterations of the system over the years asequipment needs have increased. Raymarinealso embraced NMEA protocols, produc-ing both NMEA 0183- and NMEA 2000-compatible equipment. In the past, though,integration with other NMEA equipmentfrom other vendors has required the use ofblack boxes to translate and distribute infor-mation from Raymarine’s protocol to theopen architecture of the various NMEAstandards.

NMEA 2000

In an effort to establish a universal approachto networking, the NMEA developed NMEA2000 so that a true “plug and play” protocolcould be established. The NMEA 2000 stan-dard is designed to allow equipment from dif-ferent manufacturers to interface with eachother—as long as they are compliant withNMEA 2000.

The problem is that in spite of this nobleeffort, NMEA 2000 is still flawed. There are sev-eral reasons for this. One is that the NMEAincluded a requirement that equipment beNMEA 2000 certified—at a hefty fee, especiallyfor equipment vendors who have already


invested heavily in an alternative protocol.Some feel that the expense involved is toomuch of a burden, which may explain whymarine electronics equipment manufacturersare not jumping on the NMEA 2000 band-wagon. In fact, as of this writing, the NMEA0183 standard is still widely used.

Further, in spite of the significant improve-ment in data transfer rates (up to 250,000 bpsper second versus 4,800 bps for the earlier 0183system, or at best 38,400 bps for the high-speed version of NMEA 0183), the system stillcan’t handle the system requirements of someof the latest equipment.

It should also be noted that this 250,000bps data transfer rate is based on a 200-meter-long network. Theoretically a 25-meter-long CAN bus—a more typical length formany recreational boats—could transfer data atas much as 1,000,000 bps per second (1 Mb),but the NMEA 2000 standard has fixed thevalue at 250,000 bps.

One example of how this thinking may beflawed is with video data transfer. On a modernboat, it’s quite conceivable that an owner maywant to have satellite TV broadcasts available atthe helm station, visible on the same screen onwhich the radar image and chartplotter displaysappear. Another example is video monitoringof an engine room area, a common practice onlarger yachts. NMEA 2000, which like theSmartCraft system is based on CAN protocol,can’t handle the data load these systems requirebecause it doesn’t have enough bandwidth.

Typically, vendors revert back to anEthernet-based addition to the NMEA 2000system to accommodate needs of this nature.Depending upon the version of Ethernet used,data transfer rates can be as high as 1 gigabit(Gb) per second. So, in the end, we still seeinstallations that use two or more networkprotocols to accommodate the needs or desiresof today’s boatowner.

TROUBLESHOOTING

The bottom line is that in spite of efforts tostandardize data transfer, no one is there yet,and this puts the burden on systems andnetwork installers to be really up to speedwith the equipment from the vendors inquestion. The only way to achieve this isthrough factory training, which is not some-thing a boatowner, or even a typical marineelectrician, has access to, nor would such ahigh level of product-specific knowledgemake sense (especially as it becomes obso-lete so quickly).

In the end, about all a boatowner ormarine electrician can expect to be able to dowith any of these networked systems is to con-firm the integrity of the electrical connectionsand wiring that tie the system componentstogether. It doesn’t matter if the network iswired with twisted pairs, CAT 5 cable, or ashielded harness; they are all basically a groupof electrical conductors inside a sheath. Inother words, although components are linkedwith specialized data cables made of very smallgauge wire (typically 18 AWG and smaller)and special connectors with tiny contactpoints, it is still “just wire.” And while thisvery small wire is primarily carrying data, it isoften also used for low-power distribution.

So many of the troubleshooting methodsI’ve described up to now apply here as well.We still need to confirm the following:

• all the points in the circuit are properlyconnected

• there is no signal degradation due to EMIor RFI

• excessive voltage drop does not existwhere electric power is being distributedthrough the network cabling

• appropriate overcurrent protection isprovided


Beyond these considerations, the systems oftoday are really “black boxes” in the sense thatthe high-tech side of things is literally “in thebox” and not field serviceable. As a trou-bleshooter, your role may consist of nothingmore than being able to trace and confirm thatthe connections are in the proper order andthere are no breaks in the length of the wirerunning between points A and B. As withshore-power AC systems and traditional DC-distribution systems with their relatively large-gauge cabling, the vast majority of problemsin data networks will almost always be “at theends,” or termination points. (There is also thepossibility of physical damage to a cable run,but this will often be obvious from a simplevisual inspection.) Your tools of choice will be:

• TDR• tone-generating circuit tracer • ohmmeter• voltmeter

Here are some basic guidelines:

• Use a TDR or tone-generating circuittracer (described in Chapter 3) to tracethe cables and confirm the integrity of thewire run. (You can also use an ohmmeterfor this task.)

If you use a TDR, remember its mini-mum operational length requirement is9 feet (2.7 m). Many of the cable lengthsyou might be testing are less than 9 feet,so you will have to add a 9-foot length ofcabling to one end of the cable beingtested to get relevant readings on theTDR. An easier and more practical optionis to use a tone-generating circuit tracer orohmmeter to “pin out” the harness.

• Use a voltmeter to test that any distrib-uted power is within acceptable limits.

• Look for solid continuity from a pin ter-minal at one end of the harness assembly

to the corresponding pin at the other end.Do a wiggle test (see Chapter 15) at theplug assembly with the meter attached.Wiggle the plug assembly while observingyour meter to see if the wire being testedalternates between continuity and opencircuit. Remember almost all harnessfailures occur at the plug ends.

• Confirm that the various wires are con-nected to the correct terminals, and thatthe individual wires have good continuity.Operational power for the various piecesof equipment in most networks has histor-ically been provided separately by the tra-ditional DC positive and negative wiringconnections to each piece of gear, alongwith grounding connections for someequipment. This concept is changing rap-idly, however, and in fact, both SmartCraftand NMEA 2000 network cables are alsoused for power distribution.

• Confirm power delivery through the com-mon power distribution/data delivery cableharness. This is relevant if an NMEA2000 network is being used to supplylow-current power to the connectedequipment in addition to transferring data.The limit for power distribution under theNMEA 2000 standard is 1 amp per deviceconnected, if needed. For devices requiringmore than 1 amp, auxiliary power supplylines are required. The NMEA 2000proprietary cables used in such a system areavailable in two configurations, describedas heavy and light cable. The heavy cable isintended for cumulative loads of up to8 amps, and the light cable is designed tohandle cumulative loads of up to 4 amps.

Signs That Troubleshooting Is Necessary

Signs of problems with networked equipmentinclude dim screen displays and “scrambled”or nonexistent data. If the equipment has a


record of satisfactory performance, do notimmediately assume the networked equip-ment is at fault. The first step is to determineif the more vulnerable wired connections arefaulty. If you have a new installation, the prob-lem may be software incompatibilities orglitches in the software itself. (Whenever I seethat a piece of gear is running or controlled byversion 1.0 of any software, I’m always suspi-cious. The programming people don’t alwaysget things perfect on the first go-round.) Ifyou suspect a software problem, call the equip-ment dealer or manufacturer to find out ifthere is a history of problems, and what thesoftware solution might be.

The next step is to positively identify thefunction of each of the networking cablesconnected to the electronic equipment, and

then determine the function of each of thepin connections in the cable assembly. You’llneed to refer to the equipment owner’s man-ual or installation guide for this information.If you don’t have the documentation, youmight as well stop. You must know what roleeach and every wire and pin play in the systemto determine if all the “dots” are connectedproperly and that the cable harness is in goodworking order.

The NMEA installation standard clearlyidentifies standard color codes for its 2000standard cable harnesses. These colors apply tothe individual conductors within the multi-conductor cable. Due to the cable design,however, you won’t really be able to see thevarious colors; you are going to have to workfrom pin to pin at the cable ends to confirmproper continuity of conductors.

Remember that failures at the connectionpoint on the equipment are not uncommon,and with a visual inspection you’ll be able tosee corrosion or loose wires. Slight corrosionhas a much more profound effect on a networksystem’s ability to distribute data than on moretraditional electrical connections, so carefullyinspect the cables and connections. Look forany signs of corrosion on the pins or socketends of the termination points. If you seeloose wires at screw and ring-eye connections,tighten them.

If you use an ohmmeter for these tests,take into account the inherent resistance of thewire, which is very small gauge, typically 16 to24 AWG (1 to 0.2 mm2). The NMEA 2000standard identifies maximum allowable resist-ance values for power runs as 1.34 ohms per100 meters for heavy-gauge network cable (16to 18 AWG) and 5.4 ohms per 100 meters forlight-gauge network cable (22 to 24 AWG).Table 17-1 identifies typical resistance valuesfor commonly used copper wire gauges as wellas the metric equivalents.


An NMEA 2000 network can distribute up to 1 amp perdevice over network wiring. Beyond that, dedicatedpower leads are required.

powersupplyconnection

wind meterdepth meter

radar unit

dedicatedpower lead for devices

+ VDCgroundshield

drop cable without power connection(provided by manufacturer)

NMEA 2000 also specifies maximum allow-able voltage drop as supplied by a battery at1.5 V, and it goes into great detail explainingstep-by-step procedures for checking each leg ofthe network as more nodes are added to the sys-tem. Use the inTELLECT meter (see Chapter 2)to determine if cabling is within the allowableparameters. Concerns with voltage drop applyto any network system, so always identify anduse specific manufacturers’ requirements. If youreally want to learn more about the intricatedetail of these systems, I strongly recommendthat you get a copy of the NMEA’s InstallationStandards for Marine Electronic Equipment Usedon Moderate-Sized Vessels, second edition. Go towww.nmea.org to order a copy (it’s not free—it’s$175 for NMEA members and $295 for non-members—but it’s worth every penny).

THE FUTURE OF ONBOARDPOWER DISTRIBUTION

Another area of onboard wiring that is rapidlychanging is power distribution to equipmentother than electronics. This applies to DC and,

in some cases, AC power. Many companieshave entered the marketplace, some of themwith systems that have been used successfully inthe commercial aircraft industry for severalyears. These same systems also use computer-based protocols to send data, and as alreadystated there are protocols in place other thanthe NMEA 2000 standard. Some are CAN-based networks just like NMEA 2000 andSmartCraft systems, and others are not.

Three-Wire Power Distribution

The basic goal behind these new power distri-bution systems is to dramatically reduce theactual amount of wiring needed on board theboat. The systems will still use the traditionalDC positive conductors and negative returnsto and from a main distribution panel. Theessential difference, though, is that these sys-tems will use only one positive conductor andone negative conductor to power multipleDC loads distributed throughout the boat.The third wire in the system will be used as atwo-way data communication cable thatwill have multiple uses, such as actual data


Ohms/ Ohms/AWG Feet/ohm 1,000 feet mm2 Meters/ohm 1,000 meters

10 980.4 1.01 5.26 304.8 3.2812 617.3 1.62 3.31 191.9 5.2114 387.6 2.58 2.08 120.6 8.2916 244.5 4.09 1.31 75.9 13.1718 153.6 6.51 0.82 47.7 20.9520 96.2 10.4 0.52 30.02 33.3122 60.6 16.5 0.32 18.9 52.9524 38.2 26.2 0.21 11.9 84.2226 24.0 41.6 0.13 7.47 133.928 15.1 66.2 0.08 4.69 213.0

Specifications are for copper wire at 77°F (25°C).

Resistance for Copper WireTABLE

17-1


coverremoved

powerdistributionconductor

powerdistributionconductor

datatransfercable

localdistribution

point

A distributed power system from Capi2 (www.capi2.com). The large-gauge red and black cables are thepower distribution conductors, and the smaller center wire is the data transfer cable. The box the cables arerunning through is the local distribution point for a given piece of equipment. Any additional cabling wouldbe tapped from this box to the specific device.

battery

cabin light cabin light

maceratorbow thruster

AM/FM radio

control panel withsolid-state switching+ overcurrentprotection

data cableDC –

DC +

A simplified view of a three-wire (positive, negative, and data) power distribution installation. It’s important to note that not all of theavailable distributed power systems emerging as of this writing are actually three-wire systems. In fact, an NMEA 2000 system, whichdistributes both data and low-level power, uses five wires in its standard cabling. Some SmartCraft cabling can incorporate as manyas eight conductors in its harness assemblies.

transmission for equipment monitoring and forswitching the device on and off. By having theprimary power delivery system shared amongvarious components, it’s fairly easy to see how adesigner could save on the number of wires inthe overall system. This not only simplifies thesystem by reducing the number of actual wiresneeded, it ultimately can be translated into ahuge reduction of weight in copper on board aboat. Considering that the price of copper hasskyrocketed over the last few years, this wholeconcept can ultimately save money just in thematerial requirements used to make up a system.

CLOSING THOUGHTS

Industry standards have yet to be established forthings like circuit protection and environmentalinstallation concerns for distributed power

systems such as these, although the ABYC isworking on them diligently. And those of us whowork within the industry are still learning aboutthese emerging systems along with the problemsand issues related to them. With the introduc-tion of each system, new questions about com-pliance with U.S. Coast Guard regulations andexisting ABYC standards get raised.

As for which system is better or worse, myopinion is that it’s too difficult to determine atthis time. All the systems we have covered havestrengths and weaknesses. Systems vary in theiramount of bandwidth, transfer capabilities, effec-tive operational length, and the number ofdevices they can incorporate into their network.And equipment vendors have yet to agree on howto standardize the various networking options.

That said, the way we check for the age-old problems has indeed advanced, and


A centralized control panel/monitor from Moritz Aerospace (www.moritzaero.com). This electronic touch-screen panel monitors all the data and power distribution circuits connected to it.

microprocessor-driven devices make theprocess of finding the old problems faster, easier,and more accurate than ever before. Onceyou’ve eliminated problems associated withcables and connectors, it’s all “in the box,” andthere is little or nothing that a boatowner ormarine electrician can do in a field situation tocorrect such problems. Production of elec-tronic equipment has “evolved” to the pointwhere servicing internal components is notcost effective or even possible.

As an example, my microwave oven recentlystopped working. As an experienced electrician,I figured it wouldn’t be a problem to fix it, anddove in headfirst. After disassembling the oven,I was sure I’d located the faulty component—the integrated circuit board. I ordered a newpart from a local appliance dealer, and ten dayslater, it arrived—at a cost of $200. I installedit . . . and the microwave still didn’t work. Mynext stop was a Best Buy, where I bought a new

microwave that did more than my old unit, andcost $300. For only $100 more initially, I couldhave saved myself several days of labor andordering and waiting for parts. Instead, Ishelled out $500 plus my labor and time.

Most of the equipment on today’s boatsfalls into the same category as my microwave.If the device is still covered under warranty,great; the company will give you a new unit. Ifnot, it may be worth sending it to the factoryfor a look, but that will depend on the overallcost of the device.

On the upside, vendors are now able topack more intelligence and functionality intoequipment than was imaginable ten years ago.And, according to several manufacturers I’veasked, the failure rate is very low—somewherebetween 1% and 5% of total units sold. Tome, the convenience and capability of the gearwe buy and use today is well worth the occa-sional failure.


A P P E N D I X A

200

Metric Equivalents

English to Metric Metric to EnglishMultiply By To Get Multiply By To Get

LENGTH

Inches 25.4 Millimeters Millimeters 0.0394 Inches Inches 2.54 Centimeters Centimeters 0.3937 Inches Inches 0.0254 Meters Meters 39.37 Inches Feet 30.48 Centimeters Centimeters 0.0328 Feet Feet 0.3048 Meters Meters 3.281 Feet Yards 0.9144 Meters Meters 1.094 Yards Miles 1.609 Kilometers Kilometers 0.6215 Miles

AREA

Inches2 645.16 Millimeters2 Millimeters2 0.00155 Inches2

Inches2 6.4516 Centimeters2 Centimeters2 0.155 Inches2

Feet2 929.03 Centimeters2 Centimeters2 0.00108 Feet2

Feet2 0.0929 Meters2 Meters2 10.764 Feet2

Yards2 8361.3 Centimeters2 Centimeters2 0.00012 Yards2

Yards2 0.8361 Meters2 Meters2 1.196 Yards2

Miles2 2.59 Kilometers2 Kilometers2 0.3861 Miles2

VOLUME

Inches3 16.387 Millimeters3 Millimeters3 6.1 x 10–5 Inches3

Inches3 16.387 Centimeters3 Centimeters3 0.061 Inches3

Feet3 0.0283 Meters3 Meters3 35.33 Feet3

Yards3 0.7646 Meters3 Meters3 1.308 Yards3

ENERGY

Ergs 10–7 Newton-meters Newton-meters 107 Ergs Joules 1 Newton-meters Newton-meters 1 Joules Joules 107 Ergs Ergs 10–7 JoulesJoules 0.2389 Calories Calories 4.186 Joules Joules 0.000948 Btu Btu 1,055 Joules Joules 0.7376 Foot-pounds Foot-pounds 1.356 Joules

Calories 0.00397 Btu Btu 252 Calories Joules/see 3.41 Btu/hr Btu/hr 0.293 Joules/see

Btu/hr 252 Calories/hr Calories/hr 0.00397 Btu/hr Horsepower 746 Watts Watts 0.00134 Horsepower

F° 0.556 C° C° 1.8 F°°F 0.556 (°F – 32) °C °C 1.8 x °C + 32 °F



A P P E N D I X B

201

ResourcesI’m often asked about websites that are useful to the marine electrician or boatowner forkeeping up to date on new developments, as well as sourcing the equipment mentionedthroughout this book. So below are some of my most frequently visited websites; some arementioned in the text, but others are just good resources for further information.

WEBSITES

AEMC Instruments, www.aemc.com. Manufacturer of highly specialized meters, such astime domain reflectometers (TDRs). Also offers power analyzers and software foradvanced electricians.

Airpax, www.airpax.net. Manufacturer of circuit breakers and ground fault circuit inter-rupters, among other things.

American Boat and Yacht Council, www.abyc.com. A great site to learn about the stan-dards that apply to electrical work, changes to standards, and educational programsavailable to both boaters and tradespeople.

Ancor Marine, www.ancorproducts.com. A good source for learning about availablewire, cable, and terminals, and for ordering specialized tools used in the trade, includ-ing the Wire Tracker tone-generating circuit tracer.

Blue Sea Systems, www.bluesea.com. A good source for electrical panels, fuses, circuitbreakers, and switches. Also offers excellent installation education materials.

Carling Technologies, www.carlingswitch.com. A great site to learn about circuit break-ers and their characteristics.

Centerpin Technology, www.centerpin.com. Manufacturer of terminal connectors forcoaxial cable and battery cable, battery clamps, and other wiring hardware.

Charles Industries, www.charlesindustries.com. A great source for inverters, regulators,and other devices discussed in the book.

E-T-A, www.e-t-a.com. A good resource for learning about circuit protection devicecharacteristics.

Extech Instruments, www.extech.com/instrument. Offers a comprehensive selection oftest equipment, including infrared thermometers.

Fluke, www.fluke.com. The manufacturer of some of the best test instruments and soft-ware solutions available to the marine electrician, including the oscilloscopes discussedin this book.

Ideal Industries, www.idealindustries.com. Manufacturer of the SureTest circuitanalyzer, circuit tracers, power quality meters, and other test equipment.

Midtronics, www.midtronics.com. Manufacturer of the Micro500XL battery and elec-trical system analyzer and the inTELLECT EXP-1000 diagnostic platform. This sitealso provides details on how conductance testing works.


2 0 2 appendix b

Midwest Corrosion Products, www.nocorrosion.com. Manufacturer of Corro-sion Block, a corrosion inhibitor and lubri-cant.

Mytoolstore, mytoolstore.com. This siteoffers good prices on some of the testequipment mentioned in this book.

National Marine Electronics Association,www.nmea.org. The NMEA site providesaccess to its standards and information onits educational programs. You can purchasethe installation standards here as well.

PMS Products, www.boeshield.com. Manu-facturer of Boeshield T-9, a corrosion pro-tectant and lubricant.

Professional Boatbuilder, www.proboat.com.Website for the magazine. For the profes-sional who wants to stay up to date, it is thesource for the latest in technological devel-opments in all areas of marine technology.

Professional Equipment, www. professionalequipment.com. A very good source formany of the test meters mentioned in thisbook, including the WattsUp? portable

watt meter from Electronic EducationDevices (www.doubleed. com).

ProMariner, www.promariner.com. A goodsource for the electrical gear mentioned inthis book as well as some test equipmentspecific to cathodic protection.

PSICompany, www.psicompany.com. Retailerfor the Newmar StartGuard DC PowerConditioner and other power supplies andconditioners.

Siemens Water Technologies, www.usfilter.com. Manufacturer of cathodic corrosionprotection systems, including silver chlo-ride reference electrodes.

Sperry Instruments, www.awsperry.com.This site offers a wide range of telecommu-nications and electronics test equipment.

Tequipment, www.tequipment.net. Retailerof testing equipment from many manu-facturers.

Yokogawa, www.yokogawa.com. Manufac-turer of high-resolution AC leakage ampclamps.

ABYC Standards of Interest for MarineElectricians and BoatownersThe ABYC standards are mentioned quite frequently in this book. I’m often asked, “Whatstandards should I be really familiar with to be better at my work as a marine electrician?”Well, here’s the list:

A-27, Alternating Current (AC) Generator SetsA-28, Galvanic IsolatorsA-31, Battery Chargers and InvertersE-2, Cathodic ProtectionE-10, Storage BatteriesE-11, AC & DC Electrical Systems on BoatsP-24, Electric/Electronic Propulsion Control SystemsTA-27, Batteries and Battery Chargers (technical information report)TE-4, Lightning Protection (technical information report)

If you use these standards, it is imperative that you understand that they are “dynamicdocuments,” which means they are constantly evolving. Therefore, be sure you are work-ing with the latest version of the standard; otherwise, you may miss out on importantchanges.

To acquire the standards, you must become a member of the ABYC. As a member,you’ll receive regular updates on the work of the technical committees on new and revisedstandards. To find out more, go to www.abyc.com.

203

A P P E N D I X C


Absorbed glass mat (AGM) battery: A lead-acid battery in which the electrolyte is heldin fiberglass plate separators. The mat, which separates the battery plates, is saturated withelectrolyte, effectively immobilizing the liquid.AC ripple: A measurable amount of AC current that will leak through a typical rectifier cir-cuit designed to convert pure AC to DC. Excessive AC ripple can be a source of electronicnoise. It can also cause batteries to overheat if they are connected to a battery chargingsource that has excessive leakage.American Wire Gauge (AWG): A U.S. measurement standard for the diameter of non-ferrous wire, which includes copper and aluminum. The smaller the AWG number, thethicker the wire, and vice versa. Although this seems counterintuitive, it is easily explained.In making wire, metal is pulled through a series of increasingly smaller dies to create thefinal wire size. The AWG number is the number of dies. The more dies, the larger thenumber and the smaller the diameter.Ampere interrupting capacity (AIC): An important fuse or circuit breaker rating thatdescribes the amount of amperage the device can be exposed to and still function as a circuitinterrupter.Anode: The negative electrode in a galvanic cell. The positive terminal in an electrolytic cell.Antenna gain: A measure of the effectiveness of a directional antenna as compared to astandard nondirectional antenna. Also called “gain.” Apparent power: The total electrical energy actually delivered by the power supply (i.e., autility company, an AC generator, or a DC-to-AC inverter).Attenuation: The amount of signal loss per given length of the cable. Available short-circuit current (ASCC): How much current can flow through a circuit inspite of resistance factors. Current available beyond a circuit breaker’s interrupting capacity. Bandwidth: A range within a band of frequencies or wavelengths. Also, the amount ofdata that can be transmitted in a fixed amount of time; the data rate supported by a net-work connection or interface. Commonly expressed in bits per second (bps).Baseband: The original band of frequencies of a signal before it is modulated for transmis-sion at a higher frequency. Typically used to refer to the digital side of a circuit when theother side is broadband or frequency based, meaning the signal is modulated. For exam-ple, in a cell phone, “RF to baseband” means pulling out the analog or digital data fromthe modulated RF signal received from the cell phone tower and converting it to pulses fordigital processing.Black box: A sealed, unserviceable electronic control box that serves various functionswithin an electronic or networked system.Bonding system: Protects a boat against stray-current corrosion by electrically tyingtogether all the metals on the boat and then connecting the bonding wires to the boat’scommon ground point.Broadband: In general, broadband refers to telecommunication in which a wide band offrequencies is available to transmit information.

204

G L O S S A R Y


Capacitance: The ratio of the electric chargetransferred from one to the other of a pair ofconductors to the resulting potential differ-ence between them.Capacitor: An electronic component used forstoring charge and energy. The usual capacitoris a pair of parallel plates separated by a smalldistance. When a steady voltage is appliedacross a capacitor, a charge +Q is stored onone plate while –Q is stored on the oppositeplate. The amount of charge is determined bythe capacitance (C) and the voltage difference(V) applied across the capacitor: Q = CV.Since the charge cannot change instanta-neously, the voltage across a capacitor cannotchange instantaneously either. Thus capacitorscan be used to guard against sudden losses ofvoltage in circuits, among other uses. Cathode: The positive electrode in a galvaniccell. The negative terminal in an electrolytic cell.Cathodic protection: Protects a boat against gal-vanic corrosion through the use of zinc anodes.Coaxial (coax) cable: A cable consisting offour components: (1) a center conductormade of either solid copper wire or strandedcopper (commonly used in marine applica-tions; (2) a dielectric material or insulator sur-rounding the center conductor; (3) a secondconductor, which is a sheath or shield made ofeither braided copper or a foil; and (4) anouter jacket that protects the cable from theenvironment and provides some flame retarda-tion. Coax is used primarily for transmissionof high-frequency signals.Code of Federal Regulations (CFR): Rulesand regulations established by the federalgovernment, covering a broad range of govern-mental branches (e.g., the U.S. Coast Guard)and topics, including the installation of boat sys-tems (Titles 33 and 46). The regulations applyto both recreational and commercial boats. Cold cranking amps (CCA): One of severalbattery ratings. The number of amps that a

new, fully charged battery at 0°F (–17.8°C)can deliver for 30 seconds and still maintain avoltage of 1.2 or more volts per cell. Compass deviation: Compass error inducedby magnetic interference (such as produced byan electrical current). The amount of error willvary proportionally based on the strength ofthe interfering magnetic field. Conductance: A measure of the ability of abattery to carry current. When a difference ofelectrical potential is placed across a conduc-tor, its movable charges flow, and an electriccurrent (amperes) appears. Conductance is theinverse of impedance.Controller area network (CAN): A serial busnetwork of microcontrollers that connectsdevices, sensors, and actuators in a system orsubsystem for real-time control applications.There is no addressing scheme used, as in thesense of conventional addressing in networks(such as Ethernet). Rather, messages arebroadcast to all the nodes in the network usingan identifier unique to the network. Based onthe identifier, the individual nodes decidewhether or not to process the message and alsodetermine the priority of the message in termsof competition for bus access. This methodallows for uninterrupted transmission when acollision is detected, unlike Ethernets that willstop transmission upon collision detection.Controller area networks can be used as anembedded communication system for micro-controllers as well as an open communicationsystem for intelligent devices. Counterpoise: A conductor or system of con-ductors used as a substitute for earth orground in an antenna system.Delta-to-Wye transformer: A transformer inwhich the primary windings are in a Deltaconfiguration and the secondary windings arein a Wye.Deutsches Institut für Normung (DIN):The German national standards institution.

2 0 5glossary

Differential GPS (DGPS): A system of land-based sites that broadcasts correction signalsfor improved GPS position accuracy. Electromagnetic compatibility (EMC): Theability of electronic equipment to operate inproximity with other electrical and electronicequipment without suffering from, or causing,impaired performance.Electromagnetic interference (EMI): Elec-tromagnetic or electrical disturbances thatresult in undesirable responses, or impede theperformance of other electrical or electronicequipment. For example, EMI is a commoncause of deviation in compasses and electroniccompass sensors. Ethernet: Originally developed by Xerox in1976, it now describes a diverse family offrame-based computer networking technolo-gies for local area networks (LANs). It is thebasis for IEEE standard 802.3.False ground: For the purposes of this book, aground connection to neutral at a locationother than the source of power. In other words,a point where an AC neutral conductor is“falsely” connected to the AC grounding (earth)conductor. Galvanic isolator: A device installed in serieswith a boat’s earth-ground conductor thatblocks low-level DC current (galvanic current)but allows passage of AC fault current. Ground fault circuit interrupter (GFCI): Adevice intended to protect people by inter-rupting an AC circuit whenever its currentlimit is exceeded.Ground fault protection (GFP) device: Adevice intended to protect equipment byinterrupting the electric current to the loadwhen a fault current to ground exceeds a pre-determined value. Also known as an RCD(residual current device) or an EPD (equip-ment protecting device).Harmonic distortion: A load where the waveshape of the steady-state current does not follow

the wave shape of the applied voltage. Thepresence of harmonics that change the ACvoltage waveform from a simple sinusoidalwaveform to a complex waveform. Harmonicdistortion can be generated by a load and fedback into the AC mains, causing power prob-lems to other equipment on the circuit.Impedance: The opposition to the flow ofalternating current in a circuit. It’s the high-frequency equivalent of resistance.Inductance: A property of a conductor or coilthat determines how much voltage will beinduced in it by a change in current.Ingress protection (IP): An internationallyrecognized standard that addresses both wateringress and dust ingress into equipment. Thehigher the IP number assigned to a given pieceof equipment, the more waterproof and dust-proof it is. Inmarsat: A satellite communications com-pany that provides voice and data services tothe maritime, transportation, and aeronauticsmarkets as well as providing general Internetaccess from any location on the globe. It wasfounded in 1979 as a British intergovernmen-tal organization (IGO) to serve the maritimeindustry. It became a private company in 1999and a public company in 2005.Institute of Electrical and Electronics Engi-neers (IEEE): A nonprofit organization that cre-ates internationally recognized standards applica-ble to electrical and electronic equipment. International Maritime Organization(IMO): A specialized agency of the UnitedNations that develops standards for safety atsea, shipping security, and prevention of waterpollution as related to ships. Japanese Industrial Standard (JIS): Specifiesthe standards used for industrial activities inJapan.Linear load: In this context, a simple resistiveload that draws current in proportion to thevoltage delivered. For example, a simple

2 0 6 glossary

incandescent lightbulb or an electric waterheater.Marine cranking amps (MCA): The numberof amps that a new, fully charged battery at 32°F(0°C) can deliver for 30 seconds, and maintain avoltage of 1.2 volts per cell or higher. Megohmmeter: A specialized ohmmeter formeasuring extremely high resistance values,sometimes referred to as an insulation resis-tance tester. Readings are typically in the mil-lions of ohms, far beyond the reading capabil-ities of a digital volt-ohmmeter (DVOM). It isoften called a “megger.”Milligauss (mG): 1/1,000 of 1 gauss, which is aunit used for measuring the flux density ofmagnetic fields. Milligauss are useful for mea-suring magnetic field levels commonly foundin the environment.Multiplexer: A communications device (blackbox) that combines several signals for trans-mission over a single medium.National Electric Code (NEC): The preemi-nent set of safety standards for electrical instal-lations. Developed and published by theNational Fire Protection Association (NFPA).National Marine Electronics Association(NMEA): The foremost standards group inNorth America that deals with marine elec-tronics installations.Network: A group of two or more computersystems linked together to share informationand hardware. Network architecture: The structure of a com-munications network. An open architectureallows adding, upgrading, and swapping ofcomponents. It can be connected easily todevices and programs made by other manufac-turers. It uses off-the-shelf components andconforms to approved standards. A closed archi-tecture has a proprietary design, making it diffi-cult to connect the system to other systems.The hardware manufacturer chooses the com-ponents, and they are generally not upgradable.

Nonlinear load: In contrast to a linear load, aload that will not have constant values in cur-rent, voltage, or resistance. Examples are elec-tronic control circuits for refrigeration systemsand motor loads. Peak capture: A feature found on better elec-trical measuring instruments that allows theuser to capture and record the maximum valuemeasured on a circuit with fluctuating values.Power factor: The ratio of real power toapparent power in an AC system. The amountof current and voltage the customer actuallyuses compared to what the utility supplies.Protocol: In the context of data communica-tion, a common set of rules, signals, and datastructures (for either hardware or software) thatgoverns how computers and other networkdevices exchange information over a network.Radiated power: The product of antennainput power and antenna power gain, expressedin kilowatts.Radio frequency interference (RFI): Radio sig-nals normally emitted from an electrical devicethat negatively impact the quality of reception inanother electronic or electrical device. Symptomsvary and can include loss of reception or, in atelevision, reduced picture quality. RFI is a com-mon problem on boats and a primary source ofequipment performance problems. Reactive power: The difference between theelectrical power delivered to a system and thepower converted to useful work. Reactive poweris stored energy that is returned to the powersource. Real power: The amount of electrical energythat is converted into useful work. Alsoknown as active power or working power.Residual current: In this context, leakage cur-rent in an AC circuit. In an AC circuit, the hotand neutral conductors cancel each other outin a true-sine-wave power supply system.When a current differential occurs betweenthe neutral and hot, this measured difference

2 0 7glossary

is referred to as residual current, and it is leak-ing somewhere into the grounding system. Sealed valve regulated (SVR) batteries: Apressurized lead-acid battery that is completelysealed, and has a pressure-controlled vent torelease excess pressure inside the battery case(e.g., due to overcharging).Sentence structure: In NMEA parlance,describes the sequence and type of data infor-mation codes that are distributed throughoutthe network. (For specific sentence codes, seethe sidebar on page 151.)Sinusoidal: Having a succession of waves orcurves, as in an AC sine wave. Specific gravity: The ratio of the density of amaterial to the density of water. In a lead-acidbattery, the specific gravity of the electrolyte isa measure of the battery’s state of charge.Standing wave ratio (SWR): The ratio of themaximum RF current to the minimum RFcurrent on the line. It can be thought of as ameasure of an antenna system’s efficiency.

2 0 8 glossary

Time domain reflectometer (TDR): A toolused to measure time delays in signal transmis-sion through conductors that correlate toexcessive resistance, or open or shorted circuits. True root mean square (RMS): In an electri-cal context, describes the algorithm a metermust have to accurately analyze a less than per-fect AC waveform.Uninterruptible power supply (UPS): Asmall battery that provides temporary powerto electronic equipment when the connectedpower supply experiences an extreme voltagedrop or total loss. Velocity of propagation (VOP): In an elec-trical context, a percentage of the speed oflight that describes the speed of currentthrough a cable. Different conductors havedifferent VOP values due to their inherentresistances to electrical current flow.

L I S T O F A C R O N Y M S

ABYC American Boat and YachtCouncil

AFCI arc fault circuit interrupterAGM absorbed glass matAIC ampere interrupting capacityASCC available short-circuit currentAWG American Wire GaugeCAN controller area networkCCA cold cranking ampsdB decibelDGPS Differential GPSDIN Deutsches Institut für NormungDVOM digital volt-ohmmeterEMC electromagnetic compatabilityEMI electromagnetic interferenceEPD equipment protecting deviceFCC Federal Communications

CommissionGFCI ground fault circuit interrupterGFP ground fault protectionGHz gigahertzGMDSS Global Maritime Distress and

Safety SystemGPS global positioning systemHz HertzIEC International Electrotechnical

Commission

IEEE Institute of Electrical andElectronics Engineers

IMO International MaritimeOrganization

IP ingress protectionJIS Japanese Industrial StandardkW kilowattmA milliampMARPA mini automatic radar plottingaidMCA marine cranking ampsmG milligaussMHz megahertzNEC National Electric CodeNMEA National Marine Electronics

AssociationPC personal computerRCD residual current deviceRFI radio frequency interferenceRMS root mean squareSWR standing wave ratioTDR time domain reflectometerUPS uninterruptible power supplyVAC volts of alternating currentVDC volts of direct currentVOP velocity of propagationWAAS wide area augmentation system

209Copyright © 2007 by Edwin R. Sherman. Click here for terms of use.


I N D E X

211

Numbers in bold indicate pageswith illustrations

Aabsorbed glass mat (AGM) bat-

teries, 15AC appliances

Energy Star, 68, 71, 72–73false grounds, 48–50, 51load analysis, 69–71load types, 77–78motor specifications, 73neutral-to-ground bonding,

48–50, 51power consumption analysis,

72–73power factor, 68, 72–73residual current from, 93–95

AC circuitsavailable short-circuit cur-

rent, 53–54, 57circuit breakers and fuses,

53–54false grounds, 48–50, 51, 56GFP and GFCI testing,

54–55, 57harmonic distortion, 78–82load analysis, 69–71polarity testing, 47–48, 55,

97, 112power factor, 68safety, 2, 67voltage drop in, 33

AC clamp-on leak tester, 8, 9,11, 95–97, 100, 101

AC current. See also AC wave-forms; residual current

balance of, 93capacitors and, 68, 78, 114,

115, 116load types, 77–78multiplication, 80, 82power factor, 67–68, 71,

72–73, 75ripple, 29, 31, 32

AC generators, 8–9, 48, 49, 50,69, 76, 98, 101

AC power sources. See alsoinverters; isolation trans-formers

generators, 8–9, 48, 49, 50,69, 76, 98, 101

load analysis, 69–71neutral-to-ground bonding,

48–50, 51shore power, 69shore-power service testing,

57, 58, 59terminal configurations

(ABYC Standard E-11),113

troubleshooting, 8–9voltage potential, 113–14

AC resistive loads, 7, 8–9, 49, 50AC waveforms

equipment performance and,75, 76–77

harmonic distortion, 78–82,87

types of, 76–77variability of, 77–78

AEMC Fault Mapper TDR, 38,40–42, 44, 201

air conditioners, 72–73Airmar WeatherStation, 162–63alphanumeric time domain

reflectometer. See timedomain reflectometer(TDR)

alternatorscharging system test, conduc-

tance battery tester, 20,21–22,

charging system test, diagnos-tic meter, 28–33, 29, 31

engine-driven alternator, 5, 6heat generated by, 63–64

aluminum, 111aluminum anodes, 107, 108American Boat and Yacht Coun-

cil (ABYC)AC load analysis (Standard

E-11), 69–71ampere interrupting capacity

(AIC) limits (Standard E-11), 54

battery charger installation(Standard A-31), 125, 127

battery charger temperature(Standard A-31), 64, 134

bonding, 108cathodic protection (Stan-

dard E-2), 104, 105, 109,110, 111

circuit breakers and fuses(Standard E-11), 54

circular mil (CM) formula(Standard E-11), 44

circular mil (CM) table(Standard E-11), 45

Corrosion Certificationcourse, 103

electrical load requirements(Standard E-11), 29, 30

galvanic isolators (StandardA-28), 65, 114, 115, 134

grounding systems (StandardE-11), 124–28, 126, 127

ignition protection (StandardE-11), 164

inverter temperature (Stan-dard A-31), 64, 134

lighting circuits standards, 5lightning protection (Techni-

cal Information Report TE-4), 120–22

membership in, 203neutral-to-ground bonding

(Standard E-11), 48–50power distribution systems,

198reverse-polarity indicator

(Standard E-11), 47standards list, 203temperature (Standards A-28

and A-31), 64, 134terminal configurations

(Standard E-11), 113voltage drop levels (Standard

E-11), 33, 43–44, 143website, 201, 203wire and cable run standards,

87American Wire Gauge (AWG),

41, 44, 45amp clamp (Midtronics), 26–27,

28, 33amp clamp, high-resolution, 4,

103, 117, 118amp clamp, inductive, 30, 95amperage, 26, 28, 29–30, 87,

138ampere interrupting capacity

(AIC), 54Ancor Marine

coaxial cable, 168


Ancor Marine (continued)coaxial cable stripper, 171,

172–73website, 201Wire Tracker tone-generating

circuit tracer, 38, 39antennas

cell phones, 183–84, 188counterpoise, 177–79, 181–82gain, 175GPS, 147, 149–50location of, 88, 138, 180, 181,

188, 189radar, 184–89, 185–87satellite communications sys-

tems, 183SSB radios, 143, 144, 177–83,

178–81, 188TV interference and GPS accu-

racy, 183VHF radios, 141, 174–77, 175,

180, 181, 184, 188apparent power, 67attenuation, 165, 168, 169, 174audio systems

AC waveform and perfor-mance of, 75

harmonic distortion, 79RFI and, 123–24troubleshooting, 12

autopilotsadvances in technology of, 156installation and troubleshooting,

132, 163–64networking, 150, 156

available short-circuit current(ASCC), 53–54, 57

Bbandwidth, 191baseband, 191batteries

advances in technology of,14–15

battery-potential stray current,117

CCA trend analysis, 20, 22conductance battery tester,

15–16, 17–19deep scan test, 25–26deterioration of, 15, 22diagnostic meter test, 23–26for electronic equipment,

136–37state of charge (SOC), 19, 25, 26

state of health (SOH), 19,26

temperature compensation test,25, 64–65

terminal testing, 63–64testing, 14–15

battery chargersEMI and, 92installation (ABYC Standard

A-31), 125, 127temperature compensation

adjustments, 65temperature standards (ABYC

Standard A-31), 64, 134troubleshooting, 7, 9–11

battery isolators, 135Bird Electronic SWR meter, 176,

177black boxes, 151–52, 191, 194boat fires, 60boatyard labor rates, 13, 83bonding systems, 105, 107–8, 117,

118, 121, 122broadband, 191

Ccable strippers, coaxial, 171,

172–73cabling. See wiringcapacitance, 78, 123capacitors, 68, 78, 114, 115, 116Capac silver/silver chloride refer-

ence electrode, 104Capi2 power distribution system,

197cathodic protection

ABYC Standard E-2, 104, 105,109, 110, 111

aluminum and, 111aluminum anodes, 107, 108magnesium anodes, 107, 111zinc anodes, 104, 105, 107,

108–14, 109, 110cell phones

antennas, 183–84, 188frequencies used by, 147, 150

Centerpin Technologies, 173, 201charging system tests

conductance battery tester, 20,21–22

diagnostic meter, 28–33, 29,31

Charles Industries inverters, 76–77,201

chartplotters, 132

circuit breakers, 53–54circuits. See also specific types of

circuitsfaults, locating, 41–43, 42separation zones, interference

and, 87–92, 160–61tracing, 37–39

circular mil (CM) formula, 44circular mil (CM) table (ABYC

Standard E-11), 45clamp-on AC leak tester, 8, 9, 11,

95–97, 100, 101clothes dryers, 49, 50coaxial cable

attenuation, 165, 168, 169, 174

cable strippers, 171, 172–73connectors for, 170–74construction of, 165, 166impedance, 166, 167, 168–69installation of, 169–74,

170–173minimum bend radius, 169,

170, 175signal loss, 168, 174tests for leakage, 101, 102types of, 167–69uses of, 165velocity of propagation (VOP),

166–67Code of Federal Regulations (CFR),

133, 164cold cranking amps (CCA) rating,

18, 19, 24, 25, 26cold cranking amps (CCA) trend

analysis, 20, 22communications equipment, 9,

11–12, 139. See also specifictypes of equipment

compassesdeviation, 142EMI and, 87, 92, 131, 132,

142installation of, 131, 132, 147satellite communications sys-

tems, 147–48computer systems. See also laptop

computersAC waveform and performance

of, 75harmonic distortion, 79networking equipment, 150,

151–52RFI and, 124

conductance, 15

2 1 2 index

conductance battery tester, 15–17battery test, 15–16, 17–19CCA trend analysis, 20, 22charging system test, 20, 21–22limitations of, 35models, 16, 35–36starter circuit test, 19–20troubleshooting with, 4, 6

controller area network (CAN),151, 191, 192, 193, 196

copper, conductivity of, 122copper foil tape, 177–79, 181, 182copper sulfate reference electrodes,

109copper wire, 63, 195, 196, 198corrosion. See also cathodic protec-

tionbattery-potential stray current,

117bonding systems, 105, 107–8,

117, 118data-logging of stray current, 85galvanic isolators, 105, 114,

115–16protection basics, 104–8, 107,

125, 126survey, 108–19tools for analyzing, 103–4,

108–19Corrosion Certification course

(ABYC), 103counterpoise, 143, 177–79,

181–82cranking amperage specifications,

26, 28cranking voltage, 19–20, 27, 28crest factor, 80

Ddaylight-viewable screens, 131,

132, 133DC current

electrical shock, 94, 95loads for common equipment,

29–30power distribution systems,

196–98stray current, 103, 111, 112,

116–19DC-powered UPS devices, 137–38,

153deep scan test, 25–26Delta-to-Wye transformer, 82depth sounders

advances in technology of, 156

cables, 157, 160cost of, 156displays, 157frequencies used by, 156, 157installation of, 132, 157interference, 160–61networking, 150operation of, 156, 157power supply for, 160transducers, 138, 157–60, 158,

159, 161troubleshooting, 160–61

Deutsches Institut für Normung(DIN) rating, 18

diagnostic meter, 22–23battery test, 23–26charging system test, 28–33, 29,

31starter circuit test, 26–28,

27troubleshooting with, 4, 5, 6, 7,

10, 11voltage drop test, 33–35

Differential GPS (DGPS), 148, 150Digital Antenna, 184digital selective calling (DSC), 139,

141digital volt-ohmmeter (DVOM)

calibration check, 108, 109corrosion survey, 103–4,

108–19extension probe, 97–98limitations of, 33tracking DC stray current,

117–19troubleshooting with, 7, 10, 11

dock potential, 113–14Dynaplate grounding plane, 178

Eelectrical load requirements (ABYC

Standard E-11), 29, 30electrical shock, 94, 95, 97–98electrical systems. See also AC

entries; DC currentadvances in, 13categories, 2–3defined, 3diagnosis of problems with, 14loads for common equipment,

29–30electromagnetic compatibility

(EMC), 153electromagnetic interference (EMI)

autopilots, 163, 164

compasses, 87, 92, 131, 132,142

electronic equipment installa-tion and, 87–90, 89, 131,132, 138, 142

radar, 153–54sources of, 88–89SSB radios, 143–44troubleshooting, 91–92VHF radios, 131, 132, 142victims of, 89–90

electromagnetic radiation, 88Electronic Education Devices

WattsUp? power analyzer, 8,71–73, 202

electronic equipment. See also net-working equipment

AC waveform and performanceof, 75

advances in, 13categories, 2, 3, 9daylight-viewable screens, 131,

132, 133defined, 3EMI and, 87–90, 89, 131, 132,

138, 142ergonomics and, 130–33, 131,

132, 138frequencies used by, 91isolating circuits, 20lightning protection for, 122loads for, 29–30power supply for, 136–38,

137reliability of, 199reverse polarity, 138RFI and, 29, 87–91, 123–24,

127–28, 138standards and regulations for,

88, 125, 127–28, 196temperature and, 133–35,

136troubleshooting, 9, 11–12,

198–99voltage parameters, 138watertight integrity, 133, 134,

138websites, 201–2

Energy Star appliances, 68, 71,72–73

engine cranking amperage specifica-tions, 26, 28

engine-driven alternator, 5, 6engine instrumentation, 6–8,

85–86, 132

2 1 3index

equipment and instruments fortroubleshooting. See alsotroubleshooting

advances in, 1brands of, 1–2choosing, 2conductance battery tester, 4, 6cost of, 1data sampling intervals, 84decisions about buying, 128diagnostic meter, 4, 5, 6, 7, 10,

11digital volt-ohmmeter

(DVOM), 7, 10, 11gauss meter, 6, 91–92infrared heat-sensing gun, 5, 7laptop computers, 9, 10oscilloscopes, 9, 10, 12SureTest circuit analyzer, 8, 10,

11time domain reflectometer

(TDR), 5, 7, 11, 12, 167, 194transistor radio, 6, 90–91websites, 201–2

equipment protecting device(EPD). See ground fault pro-tection (GFP) device

ergonomics, 130–33, 131, 132, 138Ethernet, 151, 190, 191, 193Extech Instruments

heat-sensing gun, 61, 62, 63–64high-resolution amp clamp,

117, 118megohmmeter, 99, 100–102oscilloscope, 74website, 201

extension probe, 97–98

Ffactor. See crest factor; power factorfalse grounds, 48–50, 51, 56Fault Mapper TDR (AEMC), 38,

40–42, 44, 201Federal Communications Commis-

sion (FCC), 88, 143, 183, 184ferrites, 153–54Fluke 867B oscilloscope, 75

cost of, 74FlukeView software, 84, 85waveform analysis, 76, 79–80, 81website, 201

fluxgate compass, 147–48fresh water vs. salt water, 94,

108–9, 111, 121Furuno NavNet network, 190, 192fuses, 54

Ggalvanic corrosion, 105, 106galvanic isolators

location of, 114, 115purpose of, 105, 115temperature and (ABYC Stan-

dard A-28), 65, 134testing, 115–16

galvanic series of metals, 104, 105,106, 109

gauss meter, 6, 91–92gel-cell batteries, 15generators, 8–9, 48, 49, 50, 69, 76,

98, 101Global Maritime Distress and

Safety System (GMDSS), 139,141

global positioning system (GPS)accuracy of, 148, 183advances in technology of, 148antenna installation, 147,

149–50DGPS, 148, 150frequencies used by, 150installation of, 148–50, 149, 188interference from TV antennas,

183networking with other equip-

ment, 139, 141, 150, 151–52,156

RFI and, 150Selective Availability (SA), 148temperature and, 150–51voltage and current require-

ments, 150WAAS, 148, 150

ground fault circuit interrupter(GFCI), 53, 54–55, 57

ground fault protection (GFP))device, 53, 54–55, 57

grounding systemsABYC and NMEA standards,

124–28, 126, 127AC and DC grounding systems,

49, 96antennas, 177–79, 181–82bonding systems, 105, 107–8,

117, 118, 121, 122lightning protection, 120–22,

121purpose of, 120residual current and, 96RFI and, 122–24tracking DC stray current,

117–19

ground loops, 123–24, 125, 127grounds, false, 48–50, 51, 56

Hharmonic distortion, 78–82, 87heat gun. See infrared heat-sensing

gunhigh-resolution amp clamp, 4, 103,

117, 118hull potential, 109–12, 114

IICOM temperature guidelines,

134–35Ideal Industries, 9, 201. See also

SureTest circuit analyzer (IdealIndustries)

ignition protection, 64, 136immobilized electrolyte batteries, 15impedance

coaxial cable, 166, 167, 168–69defined, 15insulation breakdown, 98–102measurements, 52–53troubleshooting tips, 53

inductance, 20, 123inductive amp clamp, 30, 95inductive loads, 78infrared heat-sensing gun, 60–61

battery terminal testing, 63–64cost of, 60models, 60operation of, 62–64, 63specifications for, 61–62temperature monitoring appli-

cations, 52, 64–65, 82troubleshooting with, 5, 7value and utility of, 64, 65–66

ingress protection (IP) rating, 133,134, 138

Inmarsat satellite communicationssystem, 145, 146, 147

Installation Standards for MarineElectronic Equipment Used onModerate-Sized Vessels(NMEA), 196

Institute of Electrical and Electron-ics Engineers (IEEE), 22

instruments. See equipment andinstruments for troubleshooting

insulation breakdown, 93, 98–102inTELLECT EXP-1000 diagnostic

meter (Midtronics). SeeMidtronics inTELLECTEXP-1000 diagnostic meter

intermittent problems, 83

2 1 4 index

International ElectrotechnicalCommission (IEC), 93, 133

International Maritime Organiza-tion (IMO), 133

invertersEMI and, 92load analysis, 69neutral-to-ground bonding

(ABYC Standard E-11), 48,49

temperature and, 64, 134, 135troubleshooting, 7, 9–11waveforms and, 76–77

isolation transformersinsulation breakdown, 98, 101neutral-to-ground bonding

(ABYC Standard E-11), 48,49

troubleshooting, 8–9isolators. See battery isolators; gal-

vanic isolators

JJapanese Industrial Standard (JIS),

18, 24, 133, 138

Llaptop computers. See also com-

puter systemsadvantages of, 85data-logging capabilities of, 79,

83, 86data sampling intervals, 84examples of uses of, 85–86RFI and, 124software for, 83, 84specifications of, 83–84troubleshooting with, 9, 10

lightbulbschecking circuits and, 42–43harmonic distortion and, 79as linear load, 77

lighting circuits, 5, 7, 69, 70, 79lightning protection, 120–22, 121,

125, 126linear AC loads, 77, 78Lowrance depth sounders, 156

Mmagnesium anodes, 107, 111magnetic field strength, 87, 91–92marine cranking amps (MCA) rat-

ing, 18, 19, 24, 25Maritime Mobile Service Identity

(MMSI) number, 141–42M. C. Miller Company, 109

megohmmeters (meggers), 99–102Mercury Marine SmartCraft net-

work, 192, 193, 194, 196, 197metals

electrical conductivity of, 122galvanic series, 104, 105, 106,

109metric conversions, 200Micronta SWR/power meter, 175,

176, 177microprocessors, 14, 199Midtronics, 201Midtronics inTELLECT EXP-

1000 diagnostic meter, 22–23amp clamp, 26–27, 28, 33battery test, 22, 23–26charging system test, 28–33, 29,

31deep scan test, 25–26infrared temperature sensor,

64–65limitations of, 35starter circuit test, 26–28, 27temperature compensation test,

25, 64–65value and utility of, 35–36voltage drop test, 23, 33–35,

196website, 201

Midtronics Micro500XL conduc-tance battery tester, 16–17

battery test, 17–19CCA trend analysis, 20, 22charging system test, 20, 21–22limitations of, 35starter circuit test, 19–20website, 201

minimum bend radius, 149–50,155, 169, 170, 175

Moritz Aerospace controlpanel/monitor, 198

motor circuits, 3, 4–5motor specifications (MotorMas-

ter+ 4.0), 73multiplexer, 150, 152, 191

NNational Council on Radiation Pro-

tection (NCRP), 153National Electric Code (NEC), 48,

51, 71, 78National Marine Electronics Associ-

ation (NMEA)calculating loss, 174coaxial cable specifications,

168–70

copper foil for counterpoise,177–78

grounding standards, 124–25,127–28

Installation Standards for MarineElectronic Equipment Used onModerate-Sized Vessels, 196

isolated battery bank, 136–37NMEA 0183 networking proto-

col, 151, 190, 192, 193NMEA 2000 networking proto-

col, 151, 192–93, 194,195–96

radar scanners, 185RFI standards, 88signal loss, 168, 174standards development, 129,

190temperature standards, 134VHF radio installation, 141, 142website, 202

navigation equipment, 9, 11–12NavNet network (Furuno), 190,

192network, 191network architecture, 191networking equipment

advances in technology of, 190Airmar WeatherStation, 162–63autopilots, 150, 156black boxes, 151–52, 191, 194choosing, 198computers, 150depth sounders, 150, 156GPS, 150, 151–52, 156multiplexer, 150, 152, 191power supply for, 195–96protocols, 151–52, 191,

192–93, 194, 195–96radar, 150, 154, 156sentence structure, 151, 191standards and regulations for,

198terminology, 191troubleshooting, 193–96types of networks, 190, 192wiring, 193, 194, 195

Newmar StartGuard DC powerconditioner, 137–38, 153,202

nonlinear AC loads, 77–78

Ooscilloscopes

advances in technology of, 74cost of, 74

2 1 5index

oscilloscopes (continued)models, 74peak capture, 79–80, 81troubleshooting with, 9, 10, 12value and utility of, 74–75, 82waveform analysis, 75, 76–77

Ppeak capture, 79–80, 81polarity testing, 47–48, 55, 97, 112polarization, 109–10position-finding systems, 148. See

also global positioning system(GPS)

pot fan, 135, 136power analyzer. See WattsUp? power

analyzerPowerboater’s Guide to Electrical Sys-

tems (Sherman), 9, 23power distribution systems, 196–

98power factor, 67–68, 71, 72–73, 75process of elimination, 6, 160–61protocols, 151–52, 191, 192–93,

194, 195–96

Rradar

antennas, 184–89, 185–87EMI and, 153–54frequencies used by, 153installation of, 132, 152–55,

154, 184–89, 185–87networking, 150, 154power supply for, 153, 154–

55safety, 153, 184

radio, satellite, 147, 183radio frequency interference (RFI),

87–88ABYC and NMEA grounding

standards, 124–28, 126, 127AC ripple and, 29autopilots, 163, 164electronic equipment installa-

tion and, 138, 150GPS and TV antennas, 183grounding systems and, 122–24ground loops, 123–24, 125,

127sources of, 88–89standards and regulations for, 88symptoms of, 87, 123troubleshooting, 90–91victims of, 87, 89–90, 123

RadioShackantennas, 183infrared heat-sensing gun, 60,

61ranges and ovens

false grounds, 49, 50load analysis, 69–71

Raymarine SeaTalk network, 152,192

reactive power, 67, 68real power, 67residual current

danger from, 93–95insulation breakdown and, 93,

98–102tools for locating, 8, 9, 11,

95–96, 98, 99–102tracing source of, 96–97voltage potential, 94, 97–98whole-boat protection, 55, 96

residual current device (RCD). Seeground fault protection (GFP)device

reverse polarity, 47–48, 138root mean square (RMS), 80, 81root mean square (RMS) multime-

ter, 9

Ssalt water vs. fresh water, 94,

108–9, 111, 121satellite communications systems,

144–48, 145, 183, 188scopes. See oscilloscopessealed valve regulated (SVR) batter-

ies, 15SeaTalk network (Raymarine), 152,

192sea trials, 83, 86Selective Availability (SA), 148sentence structure, 151, 191Shakespeare

antennas, 183, 184solderless coaxial cable connec-

tor, 173SWR meter, 176, 177

shore power. See AC power sourcesshore-power isolation transformers.

See isolation transformersside flashing, 121, 122Siemens Water Technologies, 104,

202signal loss, 168, 174silver/silver chloride reference elec-

trode, 85, 103–4, 108,109–14, 116

sine waves. See AC waveformssingle-sideband (SSB) radios

antennas, 143, 144, 177–83,178–81, 188

counterpoise, 143, 177–79,181–82

EMI and, 143–44frequencies used by, 143–

44installation of, 143–44operation of, 142range of, 142regulations for use, 143safety, 182temperature guidelines, 134–

35voltage and current require-

ments, 142–43SmartCraft network (Mercury),

192, 193, 194, 196, 197software, 83, 84, 195Sperry Instruments

gauss meter, 91–92website, 202

standing wave ratio (SWR), 176standing wave ratio (SWR) meter,

174, 175, 176–77starter circuit tests

conductance battery tester,19–20

diagnostic meter, 26–28, 27starter motors, 28StartGuard DC power conditioner

(Newmar), 137–38, 153, 202stray current

bonding and, 105, 107–8data-logging of, 85DC current leakage, 103, 111,

112, 116–19SureTest circuit analyzer (Ideal

Industries), 46, 47adapter, 57, 58, 59available short-circuit current

(ASCC), 53–54, 57cost of, 46false grounds, 48–50, 56GFP and GFCI testing, 54–55,

57impedance measurements,

52–53limitations, 48polarity testing, 47–48, 55, 97,

112shore-power service testing, 57,

58, 59troubleshooting with, 8, 10, 11

2 1 6 index

value and utility of, 59voltage drop measurements,

51–52, 53, 56voltage measurements, 50–51,

52, 56website, 201

TTDP Electronics antennas, 183telephones, 145, 146. See also cell

phonestelevision, 12, 75, 88, 123television, satellite, 124, 147, 183,

188temperature. See also infrared heat-

sensing gunbattery chargers and, 64, 65,

134battery isolator, 135electronic equipment and,

133–35, 136fans, 135, 136galvanic isolators and, 65, 134GPS and, 150–51inverters and, 64, 134, 135SSB radios and, 134–35standards and regulations for,

64, 134–35starter motors and, 28wiring and, 63

temperature compensation test, 25,64–65

3M Scotch 2228 Rubber MasticTape, 173, 174

time domain reflectometer (TDR),38

cost of, 38, 40limitations of, 42–43locating faults with, 41–43, 42,

117models, 40tracing circuits with, 37troubleshooting with, 5, 7, 11,

12, 167, 194value and utility of, 44velocity of propagation (VOP),

40–42, 44, 167wire sizing, 43–44, 45

Times Microwave Systems, 168tone-generating circuit tracers,

37–39, 44, 194transducers, 138, 157–60, 158,

159, 161transformers, 77–78, 82, 101. See

also isolation transformerstransistor radio, 6, 90–91

troubleshooting. See also equipmentand instruments for trou-bleshooting

AC power sources, 8–9audio and video systems, 12autopilots, 132, 164basic steps, 11–12battery chargers, 7, 9–11corrosion survey, 108–19depth sounders, 160–61electronic equipment, 9, 11–12,

198–99EMI, 91–92GFCIs, 55impedance, 53inverters, 7, 9–11isolation transformers, 8–9networking equipment, 193–

96RFI, 90–91voltage, 52voltage drop, 53

UUnderwriters Laboratories (UL), 93uninterrupted power supply (UPS)

devices, 79, 137–38, 153unity power factor, 67, 75U.S. Coast Guard

ignition protection, 164lighting circuits standards, 5power distribution systems, 198TV interference and GPS accu-

racy, 183waterproof definition, 133

U.S. Department of Energy, 73

VVectronics SWR meter, 176, 177velocity of propagation (VOP),

40–42, 44, 166–67VHF radios

antennas, 141, 174–77, 175,180, 181, 184, 188

digital selective calling (DSC),139, 141

EMI and, 131, 132, 142features of, 139frequencies used by, 139Global Maritime Distress and

Safety System (GMDSS), 139,141

GPS networking with, 139, 141installation of, 131, 132,

140–41range, 139–40

signal loss, allowable, 174standing wave ratio (SWR)

meter, 174, 175, 176–77watertight integrity, 133

video systems, 12, 75, 79, 123–24voltage

cranking voltage, 19–20, 27, 28diagnostic meter test, 26–28, 27electronic equipment parame-

ters, 138harmonic distortion, 78, 80measurements, 50–51, 52, 56minimum cranking voltage, 20spikes, 20troubleshooting tips, 52

voltage dropacceptable levels, 33, 43–44,

143 (Standard E-11)in AC circuits, 33during engine cranking, 28impedance measurements,

52–53measurements, 51–52, 53, 56significance of, 33test, 23, 33–35, 196troubleshooting tips, 53

voltage potentialbattery-potential stray current,

117dock potential, 113–14hull potential, 109–12, 114measurement of, 97–98salt water vs. fresh water, 94,

108–9, 111volt-ohmmeter. See digital volt-

ohmmeter (DVOM)

Wwaterproof equipment, 133watertight integrity, 133, 134, 138WattsUp? power analyzer (Elec-

tronic Education Devices), 8,71–73, 202

weather systems, 156, 161–63, 162websites, 201–2whole-boat protection, 55, 96wide area augmentation system

(WAAS), 148, 150wiggle test, 160, 194wind instruments, 161–63, 162Wire Tracker tone-generating cir-

cuit tracer (Ancor Marine),38, 39

wiringchecking wire size, 41, 43–44,

45

2 1 7index

2 1 8 index

wiring (continued)circular mil (CM) formula, 44circular mil (CM) table

(ABYC Standard E-11), 45coiling vs. flaking, 149–50,

160depth sounders, 157, 160grounding systems, 125, 127insulation breakdown, 98–102lightning protection and,

121, 122minimum bend radius,

149–50, 155networks, 193, 194, 195

power distribution systems,196–98

radar, 152, 153–55, 154RFI and, 123–24satellite communications sys-

tems, 145–48shielding of, 123–24SSB radios, 143, 144, 182temperature and, 63velocity of propagation

(VOP), 40–42, 44VHF radios, 140–41

World Health Organization(WHO), 153

XXantrex Xanbus network, 192

YYokogawa clamp-on leak tester, 9,

11, 95–96, 202

Zzinc anodes, 104, 105, 107,

108–14, 109, 110

Business

[Edwin sherman] advanced_marine_electrics_and_elec(bookos.org)