Hvac 8

Study Guide

CommercialRefrigeration andHVAC/R Maintenance

INSTRUCTIONS TO STUDENTS 1

LESSON ASSIGNMENTS 5

LESSON 1: COMMERCIAL REFRIGERATION SYSTEMS, PART 1 7

EXAMINATION�—LESSON 1 19

LESSON 2: COMMERCIAL REFRIGERATION SYSTEMS, PART 2 23


LESSON 3: INSTALLING AND MAINTAINING HVAC/R SYSTEMS 39


REVIEW QUESTION ANSWERS 53

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INTRODUCTIONThis study guide concludes your course in HVAC/R technol-ogy. It first focuses on refrigeration systems, both commercialand domestic. It then provides a more general guide to thetypes of installation, maintenance, and troubleshooting workcarried out by HVAC/R technicians every day.

This part of your program is based on the textbook, Funda-mentals of HVAC/R. It’s divided into nine assignments; eachassignment covers a specific area of the HVAC/R trade. Thestudy material for your program consists of

1. Your textbook, Fundamentals of HVAC/R. It contains the assigned readings and review exercises at the end of each unit. These are assigned as self-check exercises.

2. This study guide, including an introduction to your program and a summary of the material you’ll cover in each lesson. This guide also contains the followingfeatures:

An assignments page that lists all of the readingassignments for your textbook

Introductions to your lessons

Listings of the self-check tests you should completeas part of each assignment

Answers to the self-check exercises

The examinations for each lesson

As you now know, your textbook is covered by the readingassignments in this guide. Your textbook, Fundamentals ofHVAC/R, is the heart of this program. It’s very important thatyou read the material in the text and study it until you’recompletely familiar with it. This is the material on which yourexaminations will be based. Each chapter begins with a list oflearning objectives. Read through the learning objectives sothat you’ll know what to expect when you read through theunit. After you complete each unit, you can use the list oflearning objectives to review the important points of the unit.

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A STUDY PLANWe’ve divided the contents of your textbook, Fundamentals of HVAC/R, into three lessons for you to study. For each les-son, you’ll read part of the textbook. Then, you’ll complete an examination on the material you read for the lesson. Thisstudy guide contains a list of your lesson assignments, aswell as the lesson examinations. Be sure to read all the materialin both the textbook and this study guide before you attempt to complete your examinations. To get the most benefit out ofeach of your lessons, we suggest that you follow these steps:

Step 1: In this study guide, read the introduction toAssignment 1. This is the first reading assignmentof Lesson 1. Pay attention to the new ideas andconcepts that are introduced, and carefully notethe pages in your textbook where the readingassignment begins and ends.

Step 2: Skim the assigned pages in your textbook to get ageneral idea of their contents.

Step 3: Now, read the assigned pages in the textbook. Tryto see the “big picture” of the material during thisfirst reading.

Step 4: Next, go back and study the assigned pages in your textbook carefully. Pay careful attention to alldetails, including the illustrations, charts, and dia-grams included in the textbook. Take notes on theimportant points and terms in a notebook, if youwish.

Step 5: At the end of the reading assignment, review what you’ve learned by completing the “ReviewQuestions” in the textbook. Write out the answerson a separate piece of paper, if you wish. Try toanswer the questions on your own without lookingthem up in the textbook. Don’t worry about makinga mistake. The purpose of answering these ques-tions is to review the material and to help yourecognize the areas that you may need to study

Instructions to Students2

again. After you’ve answered the “Review Questions,”look up the answers in the textbook to confirm that you answered the questions correctly. If youanswered any questions incorrectly, review thematerial for that topic until you’re sure that youunderstand it. Note that the “Review Questions” areprovided only for you to review your learning. Youwon’t be graded on the “Review Questions” in anyway. Do not send your “Review Questions” answersto the school.

Step 6: Repeat Steps 1 through 5 for each of the remainingreading assignments in the lesson.

Step 7: When you’ve finished reading all the assigned textbook pages for the lesson and you’re sure thatyou’re comfortable with the material, complete theexamination for that lesson. Remember that thelesson examinations are contained in this studyguide. Each examination contains a number ofmultiple-choice questions. Take your time as youcomplete the examination—there’s no time limit.You may go back to your textbook to review materialat any time when you’re working on the examina-tion. When you’re finished with each examination,submit your answers to the school for grading.

Step 8: Repeat these steps until all three lessons have beencompleted.

Remember, you may ask your instructor for help whenever youneed it. Your instructor can answer your questions, provideadditional information, and provide further explanation ofyour study materials. E-mail your questions to your instruc-tor, and he or she will see to it that you receive the neededinformation.

Your instructor’s guidance and suggestions will be very help-ful as you progress through your program. Now, look over thelesson assignments and then begin Lesson 1.

Good luck with your program!

Instructions to Students 3

NOTES

Instructions to Students4

Lesson 1: Commercial Refrigeration Systems, Part 1For: Read in the Read in

study guide: the textbook:

Assignment 1 Pages 8–11 Pages 1283–1314



Examination 01488700 Material in Lesson 1

Lesson 2: Commercial Refrigeration Systems, Part 2For: Read in the Read in






Lesson 3: Installing and Maintaining HVAC/R SystemsFor: Read in the Read in






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NOTES

Lesson Assignments6

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Commercial RefrigerationSystems, Part 1In this lesson, you’ll continue learning about the functionsand operating methods of refrigeration system components,with a particular focus on those components used in com-mercial refrigeration systems. Your textbook introducesseveral special-application machines used for flash freezing,dispensing dairy products, displaying refrigerated products,and making ice.

This lesson also describes how various types of controls,including mechanical, temperature, pressure, and electrical,enhance the operation of commercial refrigeration systems.You’ll learn about the function of devices such as receivers,filter driers, and other special components used in commer-cial refrigeration systems. Throughout these assignmentsyou’ll consider the decision process that goes into selectingrefrigeration equipment and how individual components areused to fill the needs of specific applications.

When you complete this lesson, you’ll be able to

Describe the various types of commercial refrigerationsystems and the differences between high-, medium-,and low-temperature systems

Explain how a multiple compressor system operates

Describe how an evaporative cooling system works

Explain how a refrigerator’s defrost cycle operates

Size a walk-in cooler or freezer

List the various types of transport refrigeration systems

Identify the useful features and limitations of the various refrigeration systems found in restaurants andsupermarkets

Commercial Refrigeration and HVAC/R Maintenance 8

ASSIGNMENT 1Read this introduction to Assignment 1. Then, study Unit 76,“Commercial Refrigeration Systems” on pages 1283–1301 and Unit 77, “Commercial Refrigeration Equipment” on pages 1303–1314, in the textbook, Fundamentals of HVAC/R.

In this assignment, we’ll begin with a review of the refrigerationprocess and the industry standards for the four temperatureranges related to commercial refrigeration. The informationyou learn from this assignment will allow you to betterunderstand how practical refrigeration systems operate and,therefore, better diagnose system problems.

Commercial RefrigerationAs you’ll recall, refrigeration is the transfer of heat from onespace to another. Whether it’s a residential (domestic) refrig-eration unit or a large commercial application, the process isthe same. Stated simply, the refrigeration process involvesliquid refrigerant absorbing heat in one area; as the refriger-ant absorbs heat, it boils and changes to a refrigerant vapor. The refrigerant vapor is pumped to another area where theabsorbed heat transfers out of the refrigerant vapor. With theabsorbed heat rejected, the refrigerant vapor condenses backinto a liquid. The process repeats until the temperature of therefrigerated space reaches the desired level.

The major difference between residential and commercialrefrigeration is that the refrigeration equipment is located at a commercial business, not at a residence. Commercialrefrigeration systems can be found in many configurationsthat vary from single stand-alone units to complex applica-tions requiring multiple refrigeration systems. You’ll find thatcommercial systems are installed and maintained by a selectgroup of refrigeration technicians dedicated to these types ofsystems.

Lesson 1 9

Reach-in Refrigeration MerchandisingReach-in refrigeration units add convenience and enhancesales for merchandise on display. These types of refrigerationsystems can have an open or closed display case, and areavailable in high-, medium-, and low-temperature ranges.The closed case has a slight advantage in efficiency, while theopen case offers the consumer unrestricted access. The con-figurations that the display takes are almost limitless. Theycan be vertical or chest type, with an assortment of shelvingoptions. The units can be placed together or they can be usedas stand-alone displays.

The self-contained reach-in fixtures have several characteris-tics that need to be considered before they’re selected. First,the compressor and condenser are contained within that onepiece of equipment. This allows the unit to be placed or movedwherever it’s needed. The only requirement is that an adequateelectrical supply needs to be provided. With a stand-aloneunit, heat rejected by the condenser goes back into the build-ing. The added heat might be an advantage in the winter(reducing heating costs), but adds to the air-conditioningload of the building during summer.

Walk-in RefrigerationWalk-in refrigeration is available in various sizes and configu-rations. It can be installed as a prefabricated knockdown type,which can be disassembled and relocated, or as a permanentinstallation. Construction methods and materials used foreither type depends on the temperature inside the refriger-ated area and the estimated life of the system. Evaporatorsand fans are carefully placed to minimize cooling loss whenany door is opened. Additional fan and liquid line controlsmay be required to improve efficiency and protect the com-pressor from slugging.

Walk-in coolers must have condensate drains that lead out of the cooled space. Proper slope of drain lines with attachedtraps are required to ensure proper condensate removal. If the refrigerated space is below freezing, the drains and trapsinside the refrigerated space will require heat, which is usually


supplied by heat tapes. Prepackaged wall or ceiling refrigera-tion units for walk-in coolers are available. Their installationis similar to that of a home window air conditioner.

The Defrost CycleThis assignment also introduces the different defrost meth-ods and equipment needed for low- and medium-temperaturerefrigeration systems. First, consider the different types ofdefrosting cycles. A medium-temperature refrigeration systemmaintains a conditioned space at 34°F–45°F, which translatesto an evaporator coil that’s 10°F–15°F cooler than the spaceit occupies. This means that during the cooling cycle, the coilis below freezing, whereas during a portion of the off cycle,the coil is above freezing. Since the space and the coil areabove freezing at least part of the time, defrosting of theevaporator coils occurs naturally. This is called off-cycledefrosting and can occur on a random or planned schedule. A random defrost cycle can be taken advantage of only if therefrigeration system has reserve capacity to cool more thanits anticipated load; the evaporator fan continues to run during the defrost cycle to accelerate defrosting. A planneddefrost cycle must be used for systems that don’t have reservecapacity. For planned defrosting, the compressor is turned off for a brief time to allow defrosting to occur. Usually, aplanned defrost cycle is scheduled when the least coolingload is expected. Now, let’s look at different methods used to defrost low-temperature systems.

Low-temperature designs exist in refrigeration systems thatnever get above freezing. In this case, some form of heat isadded to defrost the evaporator coils. The supplied heat comesfrom either internal or external sources.

Internal-heat defrost (also referred to as hot-gas defrost), injectshot gas from the compressor’s discharge line into the evapo-rator coil, causing the evaporator coil to defrost. While a singleevaporator system requires a simple T connection at the expan-sion valve to allow hot-gas defrosting, multiple evaporatorsystems require that the hot gas be injected between theexpansion valve and the refrigerant distributor to ensureequal distribution of the hot gas. On systems that use forced

Lesson 1 11

air to cool the space, the defrost cycle is usually initiated bya timer and stopped either by a timer or when a predeter-mined temperature is reached. A successful hot-gas defrostrequires that specific actions occur in the proper sequence.These actions are as follows:

1. The hot-gas solenoid opens.

2. The evaporator fans turn off.

3. The compressor must continue to run.

4. The hot-gas defrost cycle continues for a predeterminedtime.

5. Drain pan heaters are energized as required.

External-heat defrost requires heat generated by anothersource to defrost the evaporator coils. The heat usuallycomes from electric heating coils placed near or imbedded in the evaporator coils. Since this method uses additionalenergy, a timer usually controls the defrost cycle. Thesequence for external heat defrost is as follows:

1. The evaporator fan stops.

2. The compressor shuts down.

3. The electric heaters are energized.

4. Drain pan heaters are energized as required.

To end the external heat defrost cycle as soon as practical, atemperature sensor, used in conjunction with the timer, stopsthe defrost process as soon as a predetermined temperatureis reached. The timer is set to end the defrost cycle in theevent that the temperature sensor fails.

After you’ve read pages 1283–1314 in the textbookFundamentals of HVAC/R carefully and completed the“Review Questions” on pages 1301–1302 and 1314, checkyour answers against those provided in the back of thisstudy guide. When you’re sure you completely under-stand the material from Assignment 1, move on toAssignment 2.


ASSIGNMENT 2Read this introduction to Assignment 2. Then read Unit 78,“Special Refrigeration Components” on pages 1315–1331 in the textbook, Fundamentals of HVAC/R.

This assignment explains the purpose of many componentsfound throughout complex systems of all types, includingcommercial refrigeration systems. The following introduces a few of these components while your textbook covers theseand several more in detail.

Solenoid ValvesOne of the most popular devices used to control fluid orvapor flow is the solenoid valve. The solenoid valve consists of an electromagnetic coil and a movable plunger that movesin response to the coil being energized and de-energized.Solenoid valves can be configured normally open (allows flowwhen the coil is de-energized), or normally closed (doesn’tallow flow when the coil is de-energized). Solenoid valves areconsidered snap-acting devices since they open or close rap-idly when the coil changes state. When installing a solenoidvalve, a technician should consider two things.

1. The solenoid valve must be installed so that the flowthrough it goes in the proper direction. A solenoid valvethat has the flow going in the wrong direction can allowflow to leak by the valve. Usually, the correct flow direc-tion is indicated on the valve body.

2. The angular position of the solenoid valve must be con-sidered. If the solenoid is positioned so that the plungerallows gravity to affect it, the valve might not close afterthe coil de-energizes. Usually, solenoid valves are installedwith the coil positioned on top.

A pilot-operated solenoid valve uses the pressure from asmaller line (controlled by the solenoid valve) to control alarger valve, which in turn controls liquid or vapor flowthrough larger pipes.

Lesson 1 13

Pressure SwitchesA typical refrigeration system has low-pressure switches,high-pressure switches, low ambient control switches, and an oil safety switch. Let’s look at how each type of pressureswitch is used to control electrical current to a refrigerationdevice.

A low-pressure switch closes (conducts) when the pressurerises above a predetermined level. Typical uses for this typeof switch are to detect a low refrigerant charge or a low tem-perature. Normally, low-pressure switches reset once thelow-pressure or low-temperature condition is corrected. If alow refrigerant charge is detected, the pressure switch dis-ables the compressor control to prevent the system fromgoing into a vacuum until the system is recharged to itsproper level.

To use a low-pressure switch as a low-temperature sensingdevice, a correlation between system pressure and the desiredtemperature must be calculated. As the temperature drops,so does the system pressure. When the temperature (in acooler for example), lowers to the desired level, the low-pres-sure switch opens; the system stops and the temperature(and pressure) begin to rise. Once the pressure reaches apredetermined level, the switch closes, starting the system to once again cool the space.

A high-pressure switch opens (stops conducting) when thepressure rises above a predetermined level. Resetting a high-pressure switch can be done manually or automatically, withmanual reset offering the greatest protection for equipment.

Typically, a high-pressure switch prevents a compressor fromoperating with excessive head pressures.

The last pressure switch we’ll discuss is the oil pressure safetycontrol. This device is used on larger compressors to ensurethat adequate oil pressure is present when the compressor isrunning. The pressure switch operates on a principle of netoil pressure, which is the compressor’s outlet pressure minusits suction pressure.


Relief ValvesRelief valves protect a refrigerant system from an uncontrolledrupture by releasing refrigerant at a predetermined maximumpressure. Relief valves are available as either spring-loaded or one-time valves. The spring-loaded relief valve will open torelieve excessive pressure, then automatically close. The one-time relief valve (also called fusible plugs) opens in responseto excessive temperature and is unable to close after relievingpressure. Due to environmental concerns related to releasingrefrigerants into the atmosphere, the spring-loaded relief valveis used most often. A relief valve is always placed in a vaporline (not a liquid line). Fusible plugs are usually located in thesuction line near the compressor to prevent the compressorshell from rupturing during a fire.

After you’ve read pages 1315–1331 in the textbookFundamentals of HVAC/R carefully and completed the“Review Questions” on pages 1330–1331, check youranswers against those provided in the back of this studyguide. When you’re sure you completely understand thematerial from Assignment 2, move on to Assignment 3.

ASSIGNMENT 3Read this introduction to Assignment 3. Then, study Unit 79,“Restaurant and Supermarket Equipment,” on pages 1332–1345,in the textbook, Fundamentals of HVAC/R.

This assignment introduces refrigeration equipment that’sunique to the restaurant and supermarket industries. Ourintroduction focuses on just one type of specialized equip-ment, which makes ice, while your textbook covers severalother types of specialized equipment in more detail.

Ice-Making Equipment, Packaged TypeFirst, let’s begin by making a distinction between ice-making(package ice) and ice-holding machines. We’ll discuss smallcommercial ice-making machines that operate between 10°Fand 32°F, produce their own ice, and have an insulated butnon-refrigerated storage section below the refrigeration unit.

Lesson 1 15

These units are self-contained and require only an electricalsupply, a water supply, and a drain for melted ice and con-densate. Ice-holding machines, on the other hand, simplystore ice that’s made at another location. Ice-holdingmachines typically maintain the storage temperature wellbelow freezing.

Making Flake and Cube IcePackage ice machines make either flake ice or some form ofsolid ice. Flake ice is formed by flowing water in a verticalrefrigerated cylinder. The water is chilled, then frozen by therefrigerated cylinder. An auger, turned constantly by a gearmotor and drive unit, shaves the ice off the inside surface ofthe cylinder. The ice is forced upward towards a dischargechute where it falls into a storage bin. Ice is made and harvested on a continuous basis as long as power is con-nected to the machine. The correct water level inside therefrigerated cylinder is maintained by a float system.

Cube ice can be made in several ways using different processes.Flat ice is formed to a specified thickness. The evaporator isthen defrosted enough for the ice sheet to release. The sheetof ice is placed on resistive heating cutting wires, which cutthe ice into a predetermined shape. Another method of mak-ing cube ice requires water to flow into preformed cups whereit’s frozen, defrosted slightly to release, and then moved tostorage. The water can be sprayed from below into the pre-formed cups. Ice can also be made in a cylindrical form. Thisis accomplished by using a tube within a refrigerated tube.Water is pumped into the inner tube. When the water pres-sure reaches a predetermined level, the refrigeration systemis turned off, the evaporator is defrosted slightly, and thewater pressure pushes the ice cylinder out.

With all of these cube ice–making systems, the ice is releasedusing defrost, which is generally accomplished by using hotrefrigerant gas that’s diverted to the low-pressure areas of theevaporator.


Water and Ice QualityThe water quality, the water flow rate, and the water level arecritical to the proper operation of the unit and should matchthe manufacturer’s instructions. To eliminate problems ofmineral buildup and defrosting problems within ice-packagingmachines, manufacturers dictate water filtration requirementsfor their machines. The type and level of filtration requireddepends on the quality of the water supply.

Package Ice Machine LocationTo ensure that the ice-packaging machine can perform itsfunction properly, several factors must be considered. First,the temperature of the incoming water must be checked, aswell as the ambient air temperature. Most ice-packagingmachines are designed to operate between 40°F and 115°F. As the temperature of both the water and ambient air goesup, the capacity of the ice-packaging machine goes down.Units located outside when temperatures are below 40°Fshould be shut off and the water drained to prevent perma-nent damage. Units installed indoors in confined areas mayneed an air-circulating fan over the condensing coils.

Troubleshooting Ice MakersTroubleshooting an ice-packaging machine is divided intothree categories: the water circuit, the refrigeration circuit,and the electrical circuit. Refrigeration circuit troubleshootingis divided into high-pressure side and low-pressure side.High-pressure problems involve checking the operation of thecondenser and verifying that the correct refrigerant chargeexists. Low-pressure problems involve checking the waterdelivery system, refrigerant delivery system, and compressor.Electrical problems may cause defrost irregularities and hothigh-voltage conductors. Electrical problems may also causelow-voltage devices to malfunction.

Lesson 1 17

After you’ve read pages 1332–1345 in the textbookFundamentals of HVAC/R carefully and completed the“Review Questions” on page 1344–1345, check youranswers against those provided in the back of this studyguide. When you’re sure you completely understand the material from this lesson, complete the Lesson 1Examination.


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1. What advantage do glass door frozen-food cases have overopen display frozen-food cases?

A. They can be used in heating mode to maintain hot food.B. Customers find them more convenient.C. They’re easier to stock with products.D. They’re more reliable.

2. Evaporative cooling is commonly used for commercial refrigeration applications located in

A. retail stores. C. hospitals.B. schools. D. greenhouses.

3. What refrigeration component makes it possible to use a single compressor to maintain multiple cases at differenttemperatures?

A. Suction line accumulatorB. Crankcase pressure regulatorC. Liquid solenoid valveD. Evaporator pressure regulator

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Commercial Refrigeration Systems, Part 1

When you feel confident that you have mastered the material in

Lesson 1, go to http://www.takeexamsonline.com and submit

your answers online. If you don�’t have access to the Internet,

you can phone in or mail in your exam. Submit your answers for

this examination as soon as you complete it. Do not wait until

another examination is ready.

Questions 1�–20: Select the one best answer to each question.

EXAMINATION NUMBER

01488700Whichever method you use in submitting your exam

answers to the school, you must use the number above.

For the quickest test results, go to

http://www.takeexamsonline.com

Examination, Lesson 120

4. What is the approximate ventilation requirement for low temperature, air-cooled condensing units?

A. 400 CFM per 1000 Btu C. 200 CFM per 1000 BtuB. 265 CFM per 1000 Btu D. 165 CFM per 1000 Btu

5. The first step in selecting commercial refrigeration equipment for a new installation is to

A. compile a list of component prices to determine how large a system the customercan afford.

B. perform a heat load calculation to determine the required BTU capacity of the system.

C. compile a list of components already in inventory so you can see what you’ll haveto choose from.

D. select the compressor because all other components will be sized to match it.

6. Why is it necessary to have controls for maintaining a minimum high-side pressure onoutdoor air-cooled condensers?

A. The refrigerant won’t condense if it’s excessively cooled.B. The chemical components in the refrigerant will separate if the pressure is allowed

to drop below the normal minimum operating pressure.C. Refrigeration metering devices require a minimum pressure drop to operate.D. Compressors won’t operate correctly if the compression ratio is too low.

7. What must be considered when performing a heat load calculation for a walk-in cooleror freezer?

A. Heat transmission, air infiltration, product, and supplemental loadsB. The volume of the case, the temperature to be maintained, and the air changes

per hourC. Heat gain through the walls, floor, and ceilingD. The style of the evaporator, the box temperature, and the type of refrigerant

8. What type of compressors do protocol refrigeration systems use?

A. Scroll C. Hermetic reciprocatingB. Rotary D. Semi-hermetic reciprocating

9. A trailer-mounted refrigeration system’s compressor is often powered by

A. a separate diesel engine.B. solar panels mounted to the top of the trailer.C. a generator operated from the wheels of the trailer.D. a large bank of batteries.

Examination, Lesson 1 21

10. What is the normal storage temperature for food items like milk, cheese, fresh fruits,and vegetables?

A. 1ºF to 32ºF C. 32ºF to 40ºFB. 25ºF to 35ºF D. 40ºF to 50ºF

11. If a reach-in freezer’s evaporator is coated with a large quantity of ice,

A. it operates more efficiently because the ice provides free cooling.B. the operation of the system isn’t affected because the coil is still below freezing.C. the system’s refrigerant level should be checked because the evaporator shouldn’t

freeze up.D. it operates less efficiently because the ice acts as insulation.

12. The defrost cycle of a low-temperature refrigerated case is often accomplished

A. by shutting off the compressor and bypassing hot gas to the evaporator.B. by shutting off the compressor and energizing electric defrost heaters. C. through normal use from customers opening and closing the doors.D. by leaving the case fans operating and shutting off the compressor.

13. Where is the refrigerant piping run from a rack system to the individual refrigerated cases?

A. On top of the floor under a protective metal coverB. In trenches under the floorC. Through an exterior wallD. Refrigerant piping isn’t necessary because rack systems are self contained

14. A water-cooled condenser’s high-side pressure can be maintained by a

A. water regulator valve. C. fan-cycling pressure switch.B. fan speed control. D. crankcase pressure regulator.

15. A flow control device stops or allows the flow of refrigerant based on an electric signal.This device is probably a(n)

A. evaporator pressure regulator. C. crankcase pressure regulator.B. automatic expansion valve. D. solenoid valve.

16. What function is performed by an evaporator’s pressure regulator?

A. It won’t allow the pressure in the evaporator to drop below its setpoint, even if thesuction pressure is lower.

B. It’s used in place of a more traditional refrigerant expansion device.C. Evaporator pressure regulator is simply another name for thermostatic expansion

valve.D. It won’t allow the pressure in the evaporator to rise above its setpoint, even if the

suction pressure is higher.


17. How do open display cases maintain the temperature within the case without any doors?

A. A curtain of cold air separates the product from the warmer store air.B. The cold air tends to stay in the display case due to the engineered air baffles that

prevent cold air from leaving the case.C. A strong, magnetic field across the opening prevents the cold air from escaping.D. Clear plastic sheets hang down in front of the product, sealing in the refrigerated air.

18. A refrigeration compressor’s net oil pressure is found by

A. subtracting the crankcase pressure from the oil pump discharge pressure.B. measuring the pressure leaving the oil pump.C. subtracting atmospheric pressure from the oil pump discharge pressure.D. adding the crankcase pressure and the oil pump discharge pressure.

19. Moisture indicators are normally part of a

A. filter-drier. C. sight glass.B. suction accumulator. D. liquid receiver.

20. Multiple parallel compressors make it possible to use multiple refrigerants in a

A. compound multistage compressor system.B. cascade system.C. two-stage cooling system.D. parallel multi-compressor system.

Commercial RefrigerationSystems, Part 2In this lesson, you’ll learn about special applications for commercial refrigeration, including transport, trucking,marine, and air cargo. You’ll then study domestic refrigera-tors and freezers. You’ll learn about the construction of arefrigerator and how the temperatures of the freezer andfresh-food portions of the refrigerator are maintained. Thelesson finishes with an in-depth discussion of refrigerationsystem troubleshooting.


Discuss how ice is formed on an ice rink

List a variety of applications for cryogenic refrigeration

Provide examples of applications where cascade-typerefrigeration systems are used

Explain how a drinking-water cooler operates

Explain the purpose and methods of quick freezing andrefreezing

Discuss the operations that take place in food processingplants, including those that make ice cream

Illustrate the features inherent in refrigerator and freezercabinet design

Maintain refrigerators and freezers

Explain troubleshooting techniques for defective com-pressors, relays, capacitors, and condensers

Understand how to search for leaks in a refrigerationsystem

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ASSIGNMENT 4Read this introduction to Assignment 4. Then, study Unit 80,“Refrigeration Applications”, on pages 1346–1361 and Unit 81,“Food Preservation,” on pages 1362–1372 in the textbook,Fundamentals of HVAC/R.

In this assignment, you’ll learn about special applications ofcommercial refrigeration systems. Each has its own opera-tional challenge that it must overcome.

Extra-Low-Temperature, Cascade, andQuick Freeze RefrigerationExtra-low-temperature refrigeration is a process that maintainsa product below 0°F. While colder refrigeration temperaturesexist in this range, they’re used mainly to fast-freeze products.The purpose of our discussion is to learn how these lowertemperatures are achieved, since using a standard single-stagecompressor would result in excessively high and damagingcompression ratios. To achieve these lower temperatures,multiple stages of compression are used, with the first stagepartially compressing the refrigerant and the second stagecompressing the refrigerant to its final pressure. Using multi-ple stages of compression reduces the compression ratio,thereby increasing the efficiency of the compressor.

To achieve even lower temperatures, refrigeration systems areconnected in series, with the condenser of one system trans-ferring heat to the evaporator of the next system. Cascadingsystems use a different refrigerant in each stage of refrigera-tion to achieve very cold temperatures.

The faster a food is frozen, the higher the quality the food willbe. To preserve foods at the highest quality requires very lowtemperatures and a process called quick freezing. When foodsare frozen slowly, ice crystals form then rupture, spoiling theoriginal quality of the product. Different foods and packagingrequirements require different fast-freeze rates, temperatures,and processes. The blast freeze method uses very low-tempera-ture air delivered at a high velocity to quick-freeze the product.Either conveyor systems or tunnels can be used to quick-freezea product individually or in quantity.

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Transport RefrigerationTransport refrigeration refers to various ways products thatrequire a conditioned environment can be moved from onelocation to another. Trucks, trains, ships, or aircraft can be involved in moving these products. Since goods must betransported through all types of climates, refrigeration sys-tems must be able to adapt to maintain the quality of theproduct.

Truck refrigeration systems can range from packing a product in ice to microprocessor-controlled stand-alonerefrigeration systems. Ice is the simplest way to maintain a cool temperature in an insulated space for a short period.This method can maintain temperatures just above freezingonly, and the product must be protected from water damageas the ice melts. Dry ice, made from solidified and compressedcarbon dioxide, is an effective way to refrigerate an insulatedspace to very cold temperatures. While dry ice is very effective,controlling the temperature of the refrigerated space isn’teasy, and the product must be protected from dehydration.Dry ice is also difficult and somewhat hazardous to handle.Liquid nitrogen and liquid carbon dioxide can produce verycold temperatures without the problems associated with reg-ular ice or dry ice. An insulated tank located under the truckstores the liquefied gas. A thermostat in the cargo area con-trols the flow of the liquid to a distribution manifold locatedat the top of the cargo area. The control allows both liquidnitrogen and liquid carbon dioxide to provide stable, con-trolled, and reliable temperatures in both the low and mediumrefrigeration ranges. These systems have proven to be anacceptable alternative to mechanical refrigeration systems.

Trucks may also use self-contained, thermostatically con-trolled, mechanical refrigeration systems to maintain a low or medium temperature in a cargo space. Smaller mechanicalrefrigeration systems can be used in conjunction with coldplates. Self-contained systems have the advantage of notneeding a remote refrigeration system or power source.Larger trucks use stand-alone nose-mount or underbellyrefrigeration systems.


A compressor can be driven by the truck’s engine or a sepa-rate gasoline or diesel engine with an electric clutch toengage or disengage the compressor, or a separate gas ordiesel engine can be used to drive a generator that produceselectricity to power a compressor motor. The compressorcapacity can be controlled by changing the speed of the com-pressor or by loading or unloading its individual cylinders.Mechanical refrigeration systems will use some type of fan tocirculate the conditioned air inside the refrigerated space.

One major concern of transport refrigeration systems isrefrigeration component weight. Most modern refrigerationsystems take advantage of lightweight materials to providereliable, efficient service with the least weight impact. Sincetruck refrigeration systems don’t have excess cooling capacity,the product should be at the correct refrigerated temperaturebefore being placed in the cargo area. To minimize heat infil-tration, the entire cargo space must be properly insulatedand mechanically maintained (seals intact, and no holesallowing outside air to infiltrate the cargo space).

Refrigeration is possible in rail cars using two methods. Themost common ways are to use a diesel-driven motor generatorto drive the compressor or use the older axle-driven compressorunit. The axle-driven unit isn’t used much anymore, sinceactive refrigeration is available only when the car is movingand it requires an external power source when the car isparked. The diesel-powered units operate, in most respects,exactly as the larger truck refrigeration systems that wealready discussed.

The refrigeration system on a ship must be able to adapt tovarious product-cooling requirements, with the method usedto power the compressor dependent on the capacity and loadon the system. Small-capacity systems might drive the com-pressors using electrical motors powered from the ship’selectrical system; large-capacity systems might drive the compressors using steam turbines powered by steam fromthe ship’s boilers. Evaporators can be forced draft, plate type,or bare tube. All of these systems must have some means todefrost the evaporators. For large refrigeration systems, hotgas may be used to defrost if the evaporators are close enoughto the compressor; if not, filtered seawater can be sprayed on

Lesson 2 27

the evaporators to remove the ice. Seawater may also be usedto cool the condensers, but since seawater is corrosive, specialmaterials must be used and periodic cleaning is required.Secondary refrigeration systems are sometimes used to reduceoil return problems associated with long, high-side piping runs.Smaller individual topside containers can have stand-alonerefrigeration systems that connect to the ship’s electrical sys-tem for power.

After you’ve carefully read pages 1346–1372 in the text-book, Fundamentals of HVAC/R, complete the “ReviewQuestions” on pages 1361–1361 and 1372. Check youranswers with those provided at the back of this studyguide. When you’re sure that you understand the materialfrom Assignment 4, go on to Assignment 5.

ASSIGNMENT 5Read this introduction to Assignment 5. Then study Unit 82,“Domestic Refrigerators and Freezers,” on pages 1373–1387 in the textbook, Fundamentals of HVAC/R.

In this assignment, you’ll learn about domestic refrigerators.As you’ll remember from your previous lessons, refrigerationis removing unwanted heat from one area and moving it toanother area where the heat isn’t a problem. Basically, therefrigerator is an electrical appliance designed to preservefoods through cooling or freezing. The refrigerator consists of an insulated box that uses the same principles and com-ponents for cooling as you learned about in your previousstudies.

Refrigerator Design and ConstructionModern refrigerators are available in a variety of designs, layouts, and colors. The common refrigerator normally hastwo doors, one for the freezer and one for the fresh-food area.Refrigerators known as over-and-under units have the freezerlocated either above or below the fresh food area. Other refrig-erators, called side-by-side refrigerators, have the fresh-foodarea and freezer alongside each other.


Refrigerator doors are usually made with hinges that can be easily changed so that the door can swing open in the opposite direction. This feature allows the refrigerator to bequickly altered to fit into a specific room layout. Compressiontype seals and magnetic-strip gaskets around the doors pre-vent air leakage. Heaters around the doors can be used tokeep the door’s external surface above the dew point andreduce sweating around the door. When installing a refrigera-tor, the levelers are usually adjusted so that the refrigeratortilts slightly to the back. This is done to cause the door toautomatically swing shut if accidentally left open. On somemodels, ice and water dispensers may be mounted in thedoor for convenience. These models reduce the number oftimes that the door is opened (which allows unwanted room-temperature air to enter and increases operating time).

The interior surfaces of a modern refrigerator are normallyplastic, making them easy to clean. Various compartments in the refrigerator may be designed to keep certain types offoods slightly warmer or colder than the main food area.

Servicing RefrigeratorsIt’s important that you have the proper tools available beforetaking any refrigerator repair call. The first step when goingon a repair call is to try to determine whether the problem ismechanical or electrical. Mechanical problems such as cabi-net problems are sometimes very easy to fix. Many problems,such as overflow of the icemaker, failure of condensate to com-pletely drain during defrost, and problems with doors can beattributed to improper leveling of the box. Older units mayrequire replacement of door gaskets, which have becomeunserviceable due to age and use.

When troubleshooting refrigerant lines and components, you’llfind that domestic refrigerators don’t have ports to attachgages. The domestic refrigerator system is sealed duringmanufacture, and the use of gages shouldn’t normally berequired. In cases where the use of gages is necessary, caremust be taken to use them properly as described in yourtextbook.

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Domestic FreezersDomestic freezers are very similar to refrigerators in generalpurpose and design. Both the refrigerator and freezer arestand-alone food storage appliances that can be movedbetween locations and operate from standard residentialpower. The major differences are that the freezer is a single-temperature device that’s usually located in an area otherthan the kitchen, and isn’t opened nearly as often as therefrigerator.

The freezer is designed for longer-term food storage, requiringthat the food be properly wrapped to prevent freezer burn.Freezer burn occurs when moisture is able to escape as vaporfrom the food into the air inside the freezer. The vapor thencondenses on the evaporator and is removed from the freezerduring the defrost cycle. Freezer burn doesn’t destroy food,but the dehydration changes the appearance and can alterthe flavor.

The domestic freezer can present a problem when initiallyfreezing food, due to its relatively low capacity. Food shouldbe frozen as quickly as possible, as occurs in a flash freezerfound in commercial food processing plants. Some freezershave a quick-freeze rack or compartment where food can beinitially placed in the freezer. If food is frozen too slowly, suchas by putting a side of beef in a domestic freezer, ice crystalswill form in the product cells, damaging the cells and alteringthe food taste and quality. If a lot of food is to be frozen, it’sbest to chill it first before placing it in the freezer.

The freezer cabinet is constructed similarly to the refrigerator.The outside of the box is normally made of sheet metal. Theinside is often made of plastic but may also contain metal that’spainted or porcelain-coated. Two types of domestic freezers areavailable, the upright and chest. The upright type of freezer issimilar in appearance to a refrigerator, with a door that swingsopen and may be hinged on either side. The upright freezertakes up less floor space than a chest freezer, making it goodfor residences where space is limited. Another asset of theupright freezer is that sometimes food can be found andaccessed with less trouble than in a chest freezer.


The chest type of freezer is usually considered more efficientthan the upright freezer because the cold air stays in thefreezer when it’s opened. The chest freezer has a lid that’sraised from the front and hinged in the back. Gaskets areused around the lid. Removable baskets store food in theupper half of the freezer. The baskets can be removed toallow access to foods stored in the bottom of the freezer. On one end of the interior of the chest freezer is the area containing the compressor. A forced-air fan coil may also be located at this end for fast freezing.

After you’ve read pages 1373–1387 in the textbookFundamentals of HVAC/R carefully and completed the“Review Questions” on page 1387, check your answersagainst those provided in the back of this study guide.When you’re sure you completely understand the mate-rial from Assignment 5, move on to Assignment 6.

ASSIGNMENT 6 Read this introduction to Assignment 6. Then, study Unit 83,“Troubleshooting Refrigeration Systems” on pages 1388–1402in the textbook, Fundamentals of HVAC/R.

In this assignment, you’ll learn about typical operating conditions and proper troubleshooting techniques related to refrigeration systems. We’ll start by looking at how to getorganized to logically resolve a problem. We’ll finish thisassignment by reviewing several common refrigeration systemproblems and the correct approach a technician should followto solve them.

Structured TroubleshootingBefore you begin adjusting, servicing, or repairing a refrigera-tion system, you must have both a thorough understanding ofhow each component of the system should normally operateand a complete understanding of how the total system shouldwork. You should also perform a complete inspection of thesystem to help properly diagnose the problem. Your inspectionshould include sampling system temperatures, pressures,

Lesson 2 31

ambient air temperature, current draws, voltages, and checking all air-moving devices. While you inspect each component, you should look for obvious problems first.

Since it’s uncommon for two or more refrigeration componentsto fail at the same time, you must consider what other problemmight have caused the failure. Newly developed refrigerantswill cause problems for inexperienced refrigeration techni-cians who can’t correlate the refrigerant temperatures andpressures to the specific application.

Typical Refrigeration System ProblemsThe following problems are common to all refrigeration systems:

Low refrigerant charge

Excess refrigerant charge

Ineffective evaporator

Inefficient condenser

Restriction in the refrigerant circuit

Inefficient compressor

Let’s take a brief look at each of these problems and howthey affect the system.

A low refrigerant charge reduces the system’s capacity by limiting the evaporator’s ability to absorb heat. With theexception of systems that use automatic expansion valves, a low refrigerant charge causes both the suction and dis-charge pressure gauges to indicate low pressure. On systemswith sight glasses, particles resembling air bubbles will bevisible. If only vapor remains in the system, a light film of oilmay cloud the sight glass. If a thermostatic expansion valveis present, a low refrigerant charge causes it to hiss whenrefrigerant is flowing through it. An experienced techniciancan determine if a low refrigerant charge exists by feelingtemperature variations throughout the system. Finally, a lowrefrigerant charge will cause the compressor to run hotterthan normal.


An excess refrigerant charge causes high discharge pressureand, with the exception of systems that use automatic expan-sion valves, can cause high suction pressure. Suction pressureat the thermostatic expansion valve may also be excessive.Capillary tubes will flow excessive amounts of refrigerant as a result of the high suction pressure. The overcharge condi-tion can be bad enough to allow liquid refrigerant to reachthe compressor (slugging). A malfunctioning evaporator mayalso cause liquid refrigerant to get back to the compressor.

An ineffective evaporator has low suction pressure and can’t absorb heat properly. An indication of an ineffectiveevaporator is sweating or frosting of the suction line at thecompressor. System symptoms can be caused by an accumu-lation of dirt on the coil, an ineffective cooling fan, blocked or incorrect airflow, icing, or a defective expansion valve. Thetechnician should carefully check the relationship betweenthe boiling temperature of the refrigerant and the tempera-ture of the ambient air entering the coil. Finally, a superheatcheck of the evaporator should be completed to ensure thatadequate refrigerant is reaching it.

An inefficient condenser (whether air- or water-cooled) doesn’tproperly transfer heat out of the system; as a result, the headpressure increases. A technician should look for improper,blocked, or a negatively influenced airflow. For instance, anew structure or building addition might change the prevail-ing wind and airflow pattern through the condenser.

A restriction in the refrigerant circuit may occur in the liquidor vapor line and result in a partial or complete blockage ofrefrigerant flow. Note: To prevent permanent damage to refrig-eration components, never knowingly allow a system with arestriction to operate for an extended time. A restriction causesa pressure drop and a temperature change across the restric-tion. Different adverse symptoms will occur depending on thelocation of the restriction. While gauges will indicate that arestriction exists, they can’t pinpoint where the restriction islocated. A visual inspection may not allow you to locate aphysically damaged line if it’s hidden from view. A restrictionin a liquid line may cause it to act like an expansion device.Some liquid line restrictions will require you to use a ther-mometer to determine the location. A plugged filter or line

Lesson 2 33

drier may cause a restriction that occurs quickly after startup.Control valves that don’t open or close completely or areimproperly positioned may cause restrictions in the system.Moisture or other contamination can cause control valves tomalfunction. Inspection of all strainers or filter screens is amust.

An inefficient compressor may be difficult to diagnose. Obvious-ly, if the compressor doesn’t run at all, it’s easy to determinethe problem. But if the compressor does run, determining itspumping effectiveness may prove more difficult. When trouble-shooting a running compressor, remember that it’s a vaporpump that draws refrigerant vapor in from the suction (low)side, then forces it out pressurized on the high side of thesystem.

Let’s finish this assignment by reviewing some sound funda-mental business practices that you should follow to improveyour relationship with customers. The way you present your-self and act when working on a job contributes to the overallsatisfaction of the customer. Always interact with and informthe customer about what you’re doing, the cost, and how longthe job will take. You should always be considerate, courteous,and orderly. Educate customers on preventive-maintenancetasks and routine inspections that they can do to preventunnecessary breakdowns and to help control expenses. If youdo these things, the customer will consider you a true profes-sional and will call you when the need arises.

After you’ve read pages 1388–1402 in the textbookFundamentals of HVAC/R carefully and completed the“Review Questions” on page 1402, check your answersagainst those provided in the back of this study guide.When you’re sure you completely understand the mate-rial from this lesson, complete the Lesson 2 Examination.


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1. The coil of a potential relay used with a small single-phase compressor found in a refrigerator should have a resistance of

A. 10,000 ohms. C. 50 ohms.B. 250 ohms. D. 1 ohm.

2. A blast freezer freezes products as they pass through using

A. a fine mist spray of liquid nitrogen.B. a high-current-draw thermoelectric cooling plate.C. a tank flooded with liquid nitrogen that the product is

dipped in.D. high-velocity low-temperature air that’s blown across the

product.

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Commercial Refrigeration Systems, Part 2








EXAMINATION NUMBER






3. What is the most common method for keeping liquefied natural gas (LNG) liquefied attemperatures of –260ºF during transport?

A. The LNG is packed in dry ice.B. A small amount of liquid is allowed to boil off to keep the remaining liquid cold.C. The LNG is cooled with large centrifugal chillers.D. LNG is naturally cold and doesn’t require any refrigeration.

4. The thermal banks in smaller trucks used for local deliveries are recharged by a(n)

A. electric compressor that operates while the truck is parked overnight.B. compressor that’s turned by a belt on the truck engine.C. small diesel engine that runs an open compressor.D. DC-powered electric compressor that operates off the truck battery.

5. The three major electrical defects in compressor motors that can be identified using anohmmeter are

A. phased, unbalanced, or blown.B. single phasing, dual phasing, and three phasing.C. open, shorted, or grounded.D. lock, under capacity, and unbalanced.

6. When troubleshooting single-phase compressor motors, it’s important that the technician

A. measure the phase displacement between the two power legs.B. check the frequency of the power source.C. check the start relay, start capacitor, and run capacitor.D. check for phase reversal between L1 and L2.

7. Freezers that freeze the product by dipping the food directly in the refrigerant are called

A. immersion freezers. C. blast freezers.B. cryogenic freezers. D. conduction freezers.

8. Why are vegetables blanched before they’re frozen?

A. To produce a bright green color and a pleasing appearanceB. To soft-freeze them prior to hard freezing themC. To extend their freshness by killing bacteria and halting enzyme actionD. To reduce the amount of energy required to freeze them

9. The refrigeration system freezes the ice for rinks by using

A. a large thermoelectric grid beneath the surface of the ice.B. coils of piping below the surface containing a brine that’s cooled with a chiller.C. coils of piping below the surface containing a saturated mixture of liquid and vapor

refrigerant being circulated by a centrifugal chiller.D. coils of piping below the surface containing liquid nitrogen that’s released to the air

after evaporating.


10. What is the purpose of refrigerating fruits and vegetables?

A. Slow down the ripening processB. Kill microorganismsC. Hasten the ripening processD. Prevent excessive drying of the food

11. To preserve its quality during long-term storage, butter should be

A. kept in hydrated containers at a temperature of 50ºF.B. stored at room temperature to preserve its texture and spread ability.C. stored in bulk at temperatures below –20ºF.D. stored at temperatures just above freezing because its quality is ruined

when frozen.

12. At what temperature would you expect an ice cream hardening room to be maintained?

A. 0º to –10ºF C. –20ºF to –30ºFB. 0º to 10ºF D. –10º to –20ºF

13. The temperature inside a refrigeration system’s compressor should be kept under300ºF because the

A. metal components inside the compressor will start to melt.B. compressor oil starts to break down above 300ºF.C. refrigerant starts to boil inside the compressor above 300ºF.D. refrigerant starts to fractionate above 300ºF.

14. Freezers that place products between horizontal or vertical refrigerated plates areknown as

A. cryogenic freezers. C. immersion freezers.B. blast freezers. D. conduction freezers.

15. What is the panel called between a domestic refrigerator/freezer’s freezer and coolercompartments?

A. The header C. The mullionB. The jamb D. The center post

16. When checking the resistance of the compressor start winding, the technician’s multi-meter shows 31 ohms. This indicates that the winding most likely

A. is open. C. is grounded.B. has continuity and is good. D. is shorted.


17. Which freezer arrangement is the most efficient?

A. Chest-type freezerB. Upright freezerC. The freezer section of a side-by-side refrigeratorD. Under-counter front-door freezer

18. The doors on a new refrigerator will close by themselves when let go if the

A. refrigerator is properly leveled when it’s installed.B. automatic motorized door operator isn’t functioning correctly.C. refrigerator isn’t properly leveled when it’s installed.D. automatic motorized door operator is functioning correctly.

19. A hole in the outer shell of a refrigerator or freezer can be a problem because

A. the magnetic field that produces the cooling effect can be reduced.B. moisture can enter, soak the insulation, and reduce its insulating ability.C. the refrigerant trapped between the inner and outer wall can escape.D. cold air can leak out, reducing the operating efficiency.

20. Why is the capillary tube soldered to the outside of the suction line on many domesticrefrigerators?

A. To provide a more leakproof seal than with mechanical connectionB. For heat exchange between the cool suction line and the warmer capillary tubeC. So the refrigerant can travel out of the cap tube, through the suction line, and into

the evaporatorD. For heat exchange between the warm suction line and the cooler cap tube

Installing and MaintainingHVAC/R SystemsAt this point in your studies, you’ve learned a great dealabout all of the components found in HVAC/R systems andhow they operate. This last lesson, which covers the last sec-tion of your textbook, concentrates on the three categories of“everyday tasks” you’ll encounter while working in the field.They’re installation, maintenance, and troubleshooting.


Discuss the factors affecting equipment placement

Demonstrate how to select and size the power wiring,disconnect, and overcurrent protection

Determine the correct charge for a new air-conditioninginstallation

List system operational safety concerns that should beaddressed on planned service calls

Explain how to address common questions asked by customers

Outline a general approach to troubleshooting

Identify common refrigeration system performance indicators

Explain how to use manufacturer provided troubleshooting aids

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ASSIGNMENT 7Read this introduction to Assignment 7. Then, study Unit 84,“Installation Techniques,” on pages 1403–1419 in the textbook,Fundamentals of HVAC/R.

Preparing for Installation A successful installation depends on more that simply openingthe shipping crate and assembling the unit. Preparation isessential, beginning with reading the manufacturer’s installa-tion instructions. The instructions contain specifications forelectrical power requirements as well as information regardingplacement and start-up procedures.

Before beginning the actual installation, local and nationalcodes should be researched along with standards of profes-sional organizations. Structural installation principles havebeen developed by the IRC (International Residential Code).The NFPA (National Fire Protection Association) publishes the NEC (National Electrical Code), which is the nationallyaccepted standard for electrical installation practices. TheUnderwriters Laboratory (UL) tests and reviews electricalcomponents, and a UL approval may be required for someHVAC/R products according to local building codes. Air-conditioning and refrigeration standards have been put forthby several organizations including the AHRI (Air-ConditioningHeating and Refrigeration Institute) and ASHRE (AmericanSociety of Heating, Refrigeration, and Air-ConditioningEngineers). Pressure vessels such as boilers, receivers, andcoolers are the concern of the ASME (American Society ofMechanical Engineers). Most importantly, before installationthe technician needs to verify that the system is correctlysized and efficiently meets the customer’s needs.

Once all the necessary preparatory steps have been taken,you’ll most likely follow these installation practices in thisorder: equipment placement, ductwork installation, pipinginstallation, electrical connections, evacuation and charging,and starting and checking.

Lesson 3 41

Equipment PlacementWhen deciding where to place equipment, first make sure thatthere’s sufficient structural strength to support the unit’sweight. Care must also be taken to ensure there’s sufficientspace for air movement, especially around condensers andfans or blowers. Sound and vibration issues must be addressedas well, with the use of isolators, isolation pads, and springswhere necessary. One very important issue that’s often over-looked is to make certain you’ve allowed ample space for serviceaccess. Even if your job description only requires you to installand not to service systems, it’s unprofessional and unfair totake a “let the next guy worry about it” attitude when consid-ering unit access.

Ductwork and Piping Installation Sizing and installing ductwork and piping has been discussedthoroughly in earlier lessons, and you can review those unitsif necessary. The importance of planning ahead for the locationand orientation of these systems as well as securing themproperly can’t be over emphasized. Also the technician mustalways use correct soldering techniques for joining piping,which includes choosing the correct torch and gas for thetype of tubing being joined. An essential part of piping andductwork installation includes checking the system for leaks.

Electrical Connections The installation technician is often responsible for the electric-al wiring that connects to the unit. The three important elements of this process are sizing the wire, sizing the over-current protection, and choosing the type of disconnect. Wiresizes are determined by consulting the NEC. The unit’s dataplate provides overcurrent protection information. As a ruleof thumb, the disconnect rating is 115% of the circuit’s mini-mum ampacity. All of these elements are important to protectthe equipment as well as the safety of the occupants andinstallation technician. It’s never safe to assume that a cir-cuit-disconnect device is functioning as intended. Always use


a meter to test for power before working on electrical compo-nents. Also make sure that all electrical connections aresecure and correctly sized connectors are installed.

Evacuation and Charging As you already know, it’s essential to check a system forleaks before starting it. Cooling systems are therefore evacu-ated and normally tested using nitrogen gas, which can besafely released into the atmosphere. Before charging, checkthe data plate to confirm the type and amount of refrigerantrequired. When charging split systems, adjust the volume tocompensate for the refrigerant-line length.

Starting and CheckingWhen starting and checking a unit, it’s very important to fol-low a set routine so that all pre-start inspection requirementsare completed in the correct order. Most manufacturers includetheir recommendations for startup in the unit’s shipping con-tainer. Typically, these recommendations include checkingclearances, mechanical components, and electrical connections.

A system’s ability to operate efficiently and according to designspecifications depends on a correct installation process. Onemissed step or incorrectly sized component could result innot only inefficient operation, but in some cases catastrophicfailure, damage to the unit, or danger to the occupants.

After you’ve read pages 1403–1419 in the textbook Funda-mentals of HVAC/R carefully and completed the “ReviewQuestions” on page 1418–1419, check your answersagainst those provided in the back of this study guide.When you’re sure you completely understand the mate-rial from Assignment 7, move on to Assignment 8.

Lesson 3 43

ASSIGNMENT 8Read this introduction to Assignment 8. Then study Unit 85,“Planned Maintenance” on pages 1420–1447 in the textbook,Fundamentals of HVAC/R.

After installing the unit, an HVAC/R technician must alsomaintain it. Planning a maintenance schedule at the time the unit is installed helps ensure that it continues to func-tion efficiently and reach its maximum lifespan. In addition,planned maintenance helps to keep small problems frombecoming large issues, saving your customers money andpreventing callbacks.

What Is Planned Maintenance?Simply stated, planned maintenance is performing regularlyschedule maintenance at pre-planned intervals to keep a unitfunctioning efficiently within its design specifications. Thereare four main components of a scheduled maintenance serv-ice call: routine maintenance, pre-start inspection, operationcheck, and troubleshooting and correction.

Routine maintenance consists of checking and replacing partssuch as filters or fluids on a regular basis. Typically, coolingsystem maintenance is scheduled in the spring and heatingsystem maintenance in the fall to prepare for the operatingseasons. Once routine maintenance is completed, the nextstep is the pre-start inspection. This begins by looking at theunit’s data plate and noting operational specifications suchas its voltage rating, amperage draw of motors, and combus-tion standards if applicable. After completing the pre-startinspection, the technician operates the unit. During the operation check, items such as the operating voltage and cur-rent as well as temperatures and pressures are compared tosystem specifications. The technician will also listen for anysounds from motors or fans, which might indicate a mechan-ical problem. Troubleshooting and correction of any problemsis the final stage of a scheduled maintenance call.


Cooling-System Maintenance Scheduled maintenance of air-conditioning and refrigerationunits calls for some special attention. Check the condenserand evaporator, clean their coils and look for damage. Changefilters when necessary, lubricate motors and fans, and tightenbelts as needed. Once the unit is started, measure motor(s)amperage draw, low-side and high-side pressures, superheatand subcooling, and evaporator pressure drops. Compare yourresults to design specifications.

Heating-System Maintenance Annual heating-system checks should include both pre-start and operational tasks. During the pre-start inspection,inspect and change filters as necessary, lubricate motors,and tighten fan belts. For all combustion type furnaces,inspect the combustion chamber. During operation, observethe flames of gas burners for correct combustion. You’ll typi-cally employ a draft gauge to measure draft readings. Thetemperature rise will also be measured and checked againstspecifications. For oil-burning furnaces, replace the nozzleand clean the cad cell sensor. During operation, there arenumerous measurements that should be taken, including theoil pump pressure, stack temperature, and carbon dioxidelevels. Check and manually adjust the barometric damper.

Regardless of fuel type, hydronic heating systems require someadditional maintenance tasks. Temperature-pressure reliefvalve function should be checked yearly, and check waterflow rate to evaluate water pump operation. Obviously, youshould inspect all piping and tanks for water leaks.

Importance of SafetyWhen you began your studies, you learned how to keep your-self safe by using correct techniques when handling tools andequipment. During a routine maintenance call, you’ll often workin an unfamiliar environment. It’s important to be aware ofyour surroundings and take note of possible danger areas,determining a path to safety before a problem occurs. Equally

Lesson 3 45

important, perform appropriate safety checks to protect the health and well-being of the customer. This may includeitems such as the correct wiring and grounding of equipment,proper support and structural integrity of components, andadequate ventilation and appropriate clearances from struc-tures and storage materials. Safety should always be yourfirst and foremost consideration.

After you’ve read pages 1420–1447 in the textbookFundamentals of HVAC/R carefully and completed the“Review Questions” on page 1447, check your answersagainst those provided in the back of this study guide.When you’re sure you completely understand the mate-rial from Assignment 8, move on to Assignment 9.

ASSIGNMENT 9Read this introduction to Assignment 9. Then study Unit 86,“Troubleshooting” on pages 1448–1467 in the textbook,Fundamentals of HVAC/R.

The new sophisticated technologies used in today’s HVAC/Rsystems offer the advantages of increasing efficiency andreducing operating costs. However, they also can make trou-bleshooting these systems more difficult. A well-trained andcompetent HVAC/R technician uses problem-solving skills tocorrectly identify deficiencies, diagnose their causes, and per-form corrective measures in a safe and efficient manner.

Communicating with Customers By this time in your studies, you’ve spent countless hourslearning about all types of components, the gas laws ofphysics, system designs, and operating principles. However,all of this knowledge has limited value if you can’t communi-cate with your customers. Once you’ve diagnosed a problemand decided on the corrective measures necessary, the next


step is explaining them to your customer and answering theirquestions. These questions generally fall into six differentcategories. These include:

How is the equipment supposed to operate? Unless the clienthas a basic understanding of how the system is designed tofunction, your explanation of the problem or your proposedsolution won’t mean much.

What is the equipment doing wrong? Once you explain theproblem, the next question arises naturally.

What is the cause of the problem? This may be the most diffi-cult question to answer since you need to briefly explain thecause without being too lengthy, or using technical jargon withwhich the client is unfamiliar.

What tests were performed to determine the cause of the problem? You might choose to give details about how certainmeasurements vary from normal operating conditions andbriefly describe what tools were used.

After the customer has a basic understanding of how the sys-tem works and what the problem is, their next question willmost likely be, how can this be corrected? In some instancesthere may be several solutions to choose from, dependingupon whether short term or long term issues need to beaddressed.

How much will this cost? Obviously, this is the most impor-tant question for most clients. Part of your answer, dependingon your employer’s policy, might require that the customersign a cost proposal with itemized pricing for both parts andlabor. Good communication goes a long way to eliminatingmisunderstandings and avoiding conflicts.

Basic Troubleshooting A good technician understands how an entire system operates,which includes understanding how all of the components areinterrelated. This is why your early studies covered so manytheories and fundamental principles, enabling you to analyzeall of the possible problems and choose the most probable

Lesson 3 47

ones. This process is known as a systems approach to trouble-shooting. There are several basic stages or phases of the troubleshooting process, which are

Understanding system operation sequence

Preliminary system inspection

Collecting operational data

Recognizing what is operating incorrectly

Testing to isolate the cause

Recommending corrective action

Troubleshooting ToolsNaturally, there are various testing instruments and traditionalhand tools used by a technician during the troubleshootingprocess. However, there are also trouble-shooting charts, pro-vided by equipment manufacturers, which are invaluablediagnostic tools. Some are simply lists of symptoms, whileothers utilize flow charts indicating how the technician canconduct tests to eliminate possible failure causes. Use ofthese charts requires a general knowledge of how the systemis intended to operate.

After you’ve read pages 1448–1467 in the textbookFundamentals of HVAC/R carefully and completed the“Review Questions” on pages 1466–1467, check youranswers against those provided in the back of this studyguide. When you’re sure you completely understand the material from this lesson, complete the Lesson 3Examination.


NOTES

49

1. To ensure that the refrigeration oil being added is clean and dry,

A. the oil should always be purchased in large containers,stored, and used as needed.

B. additives such as acid reducer and moisture inhibitorsshould be added to the oil before every use.

C. the oil container should remain open for at least an hourprior to use to ensure that all volatile organic compoundshave evaporated.

D. the oil should only be purchased in containers that will beused up after opening.

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nLesson 3

Installing and Maintaining HVAC/R Systems








EXAMINATION NUMBER






2. The disconnect current for a piece of air-conditioning equipment should be equal to

A. the sum of the compressor RLA and the FLA of all fan motors.B. 115% of the minimum circuit ampacity listed on the equipment data plate.C. the minimum circuit ampacity listed on the equipment data plate.D. 115% of the maximum overcurrent rating listed on the equipment data plate.

3. Before checking the switches in the circuit to a nonfunctioning load, the technicianshould first check

A. the resistance of the nonfunctioning device.B. line voltage, control voltage, and voltage to the nonfunctional component.C. the resistance of all the devices in the same circuit with the nonfunctional device.D. the current draw of the nonfunctioning device.

4. Before starting a new air-conditioning unit, the technician should

A. ohm out all electrical components.B. perform both a mechanical and electrical pre-check routine.C. check the unit amp draw.D. check the system superheat.

5. What type of fuses should be used for overcurrent protection of air-conditioning equipment circuits?

A. Fast-blowing fuses for added safetyB. One-time fusesC. Time-delay fusesD. Air-conditioning equipment doesn’t require overcurrent protection because of its

inherent thermal protectors.

6. The diagnostic board on a system is flashing three short flashes, pausing, then flashingtwo long flashes. This most likely is displaying

A. the ICM is faulty. C. fault code 32.B. the date. D. the suction pressure—32 psig.

7. The minimum clearance to allow from the service access panel of a piece of equipment is

A. 1 foot. C. 3 feetB. 2 feet. D. 4 feet.

8. When installing a typical split system small commercial refrigeration system, the condensing unit normally contains

A. enough refrigerant for both the condensing unit and the evaporator, but not therefrigerant lines.

B. no refrigerant, just a nitrogen-holding charge.C. enough refrigerant for the entire system, including a set length of lines.D. enough refrigerant for just the condensing line alone.


9. What side of an air-conditioning evaporator coil generally collects dirt?

A. Both sides build up dirt equally.B. The side where air enters the coilC. Dirt won’t build up on an air-conditioner evaporator coil.D. The side where air exits the coil

10. Before opening an oil fill crankcase plug on a semi-hermetic compressor,

A. the crankcase should be pressurized to facilitate quick oil removal.B. the compressor should be started to make sure the oil is warm while it’s being

drained.C. pressure should be removed from the compressor crankcase.D. an oil defector shield should be in place to handle the small amount of oil spray

that will come out when the plug is removed.

11. A technician notes that an operating air-conditioning system has ice formed on thesuction line at the condensing unit. The technician can reasonably assume that the

A. refrigerant charge is low. C. refrigerant charge is high.B. condenser coil is frozen also. D. evaporator coil is also frozen.

12. What is the purpose of checking the supply voltage after starting the system?

A. To determine which power leg is positive and which is negativeB. To determine the voltage drop in the motorC. To determine the refrigeration coefficient of performanceD. To verify that the supplied voltage is within the manufacturer’s specifications

13. A technician needs to check the heating operation of a heat pump that has no gaugeaccess ports. The technician should start by

A. checking the temperature rise across the indoor coil.B. installing bolt on piercing valves on both the high and the low side of the compressor.C. recovering the system refrigerant using piercing pliers and installing permanent

braze on service valves.D. installing bolt on piercing valves on both the gas line and the liquid line.

14. How does performing planned maintenance save the customer money?

A. The customer will receive money saving coupons to purchase new equipment.B. The customer can apply for the federal air-conditioning maintenance tax credit.C. Reduced operational cost and longer equipment lifeD. Most air-conditioning contractors perform seasonal maintenance at no or reduced

cost as a public service.


15. When installing a split system, what should be done prior to opening the installationvalves?

A. Add a small quantity of water to prevent the O-rings in the valves from drying out.B. Purge the lines and coil with nitrogen to ensure that they’re clean.C. Heat the valve body with a torch to loosen it so it’ll turn freely.D. Evacuate the lines and coil.

16. A problem that can look like refrigerant overcharge if a service technician ignores subcooling and superheat is

A. low evaporator airflow.B. high evaporator airflow.C. low condenser airflow.D. an overfeeding expansion device.

17. Why should caution be exercised when replacing a low-efficiency air filter with ahigher-efficiency air filter?

A. It’s possible for air that’s too clean to increase the occupant’s sensitivity to allergens.

B. Higher-efficiency filters have a higher pressure drop, which can cause poor airflow.C. Air-conditioning coils depend on a certain amount of small particulates to help

moisture precipitate out of the air.D. The lower pressure drop across high-efficiency filters can cause the blower motor to

draw high amps.

18. What is the purpose of checking the supply voltage before operating the system?

A. To verify that the supplied voltage is within the manufacturer’s specificationsB. To figure out where to connect the power wiring to the unitC. To determine the voltage drop in the wireD. To determine which power leg is positive and which is negative

19. An air-conditioning system that’s undercharged will operate with a

A. high subcooling and a low superheat.B. low subcooling and a low superheat.C. low subcooling and a high superheat.D. high subcooling and a high superheat.

20. Why should service technicians be familiar with company pricing policies?

A. Cost is often the foremost question in the customer’s mind.B. The technician should always try to sell the service customer new equipment.C. Technicians should always try to use parts and refrigerant that are on sale first.D. Most customers aren’t concerned with the cost, leaving the technician entirely in

charge of repair costs.

Unit 76

1. The equipment design must ensure that the quality ofthe product being cooled remains satisfactory, a mini-mum amount of energy must be used to perform theoperation, and the process must be operated to complywith the laws relating to protecting the environment.

2. High, medium, low, and cryogenic temperatures

3. Below 40°F and above 32°F

4. Frozen foods

5. Low temperature

6. Cryogenic methods

7. Compressor, condenser, metering device, and evaporator

8. High/low pressure control, condenser fan, receiver tank,suction to liquid line heat exchanger, filter drier, evapo-rator fan, thermostat, and suction line accumulator

9. Multiple evaporator systems

10. A check valve

11. Conventional thermostat, a suction pressure cut-outcontrol, or an evaporator pressure regulator

12. Multiple compressor systems

13. The suction line from the evaporator feeds the first compressor. Then the discharge from the first compres-sor enters the suction of the second compressor. Thedischarge from the second compressor goes to the condenser.

14. Evaporative cooling systems

15. A secondary refrigerant is a fluid cooled by direct refrig-eration and used to transfer cooling to a distant areawhere cooling is needed and long direct expansion linesaren’t practical or economical.

16. Brines

17. Calcium chloride, sodium chloride, ethylene and propyleneglycols, methyl alcohol, and glycerin

18. N-type and P-type

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19. An expendable refrigerant is one that performs coolingby permitting the liquid refrigerant to boil at atmosphericpressures and is released to the atmosphere after thecooling operation is completed.

20. Absorption systems

21. This means it changes from a solid to a gas without aliquid phase.

Unit 77

1. Food service, printing industry, dry-cleaning processes,and pneumatic control systems

2. These systems can be classified as high-temperature,medium-temperature, or low temperature applications.High-temperature applications are systems designed to maintain case temperature of 47°F to 60°F. Medium-temperature applications are systems designed to maintaincase temperature of 28°F to 40°F. Low-temperature appli-cations are systems designed to maintain case temperatureof 0°F to –20°F.

3. A drain line from the evaporator’s drain is connected to afloor drain, or it may be fed into a heated pan.

4. To prevent some of this warm air from entering the case,some systems will have a door switch that will shut offthe fans when the door is opened.

5. Since most refrigeration systems operate at evaporatingtemperatures below 32°F, frost will accumulate on anevaporator surface. This frost must be removed on a reg-ular basis; otherwise it will begin to insulate the surfaceof the evaporator and prohibit the transmission of heatfrom the product to the refrigerant within the evaporator.

6. Using the air within the case, resistive heaters, dischargevapor from the compressor

7. A defrost cycle can be terminated based on temperature,pressure, or time.

8. Average usage and heavy usage

Review Question Answers54

9. Heat transmission, air infiltration, product load, andsupplemental loads

10. Before any of the system components can be selected,the required BTU capacity of the system must be deter-mined by performing a heat load calculation.

11. Low-temperature condensing units will require approximately 200 CFM per 1000 BTU.

Medium-temperature units will require approximately165 CFM per 1000 BTU.

12. The condensing unit will also need some means of keep-ing the high-side pressure above a minimum valueduring low outdoor temperatures.

13. (1) The air pattern of the evaporator must envelop theentire room. (2) Never install an evaporator above a door.(3) Don’t install an evaporator coil in an area where itwill interfere with the cooler’s aisles or storage racks. (4) The evaporator should be installed in a location thatwill provide the shortest possible distance between it andthe condensing unit. (5) The location of the condensatedrains should provide for minimum pipe length.

14. Cooling a secondary refrigerant for a building air conditioning system; ice rinks

15. Liquid chillers are available with reciprocating, scroll,screw, or centrifugal compressors.

16. A health switch is a temperature switch that alerts acustomer that the machine is operating above a safeoperating range for a period of time.

17. Increases efficiency

18. Refrigerated air driers are designed to lower the tempera-ture of the air below its dew point temperature so waterwill condense out of it.

19. These systems can either use a separate diesel or gasengine or the vehicle’s engine to operate the compressor,and an electric generator to operate any other systemcomponents, or the entire system can be powered from a land line when the truck isn’t on the road.

Review Question Answers 55

20. Some train refrigeration systems will use an absorptionsystem or steam jet system to refrigerate their products.

Unit 78

1. An evaporator pressure regulator (EPR) is a refrigerantflow control device that prevents the refrigerant pressurein the evaporator from operating below a minimumvalue.

2. A crankcase pressure regulator (CPR) is a commonaccessory added to many low-temperature refrigerationapplications such as walk-in and reach-in freezers.

3. It’s a close-on-rise regulator.

4. A solenoid valve is a flow control device that stops orallows the flow of a refrigerant in a refrigeration system.

5. Normally there will be an arrow stamped on the body ofthe valve to indicate the direction of refrigerant flow.

6. They’re normally used to either stop or start a motorduring its normal cycle or on a fault condition.

7. A mechanical pressure control is basically an electricalswitch controlled by a pressure bellows. As more or lesspressure is applied to the diaphragm of its bellows, amechanical linkage will cause the electrical switch toeither open or close.

8. They’re normally used as safety controls.

9. An oil pressure control shuts down a compressor if aninsufficient amount of oil is being fed to the bearingswithin a compressor.

10. It’s a close-on-rise pressure control.

11. Mechanical temperature controls will have a sensing ele-ment filled with some type of fluid. As the temperature ofthe sensing element changes, the pressure of the fluid inthe sensing element will also change. The fluid pressureis then transmitted to a diaphragm, which through amechanical linkage will open or close on a mechanicalswitch.


12. Because there’s a relationship between the coil tempera-ture and temperature of the air entering the evaporator

13. One method of elevating the system discharge pressureis to control the operation of the condenser fan motors.Another method of maintaining a minimum condensingpressure is the use of a pressure regulator with a built-in bypass feature.

14. An automatic relief valve and a one-time relief valve

15. A suction line accumulator is a safety device that helps prevent liquid refrigerant from returning to thecompressor.

16. An oil separator is used to separate and collect some ofthe oil in the discharge line as it leaves the compressorand return it to the compressor’s crankcase.

17. A receiver is a vessel that allows a system to store excessrefrigerant that it doesn’t currently need.

18. A suction-to-liquid line heat exchanger can be added to a system to improve its efficiency and help to prevent liq-uid from returning to the compressor.

19. It maintains a desired high-side pressure and also providea means of completely stopping the flow of water duringthe off cycle.

20. A sight glass

Unit 79

1. The advantages of remotes systems are: they won’t addadditional heat to the kitchen; their condensers aren’tlocated in a greasy environment; when they’re serviced,technicians don’t have to interfere with the kitchen oper-ation. The disadvantages of remote systems are: they’renot easily relocated; their initial cost to install is moreexpensive; they use more refrigerant and refrigerant piping.

2. The ability to satisfactorily clean the equipment, provideadequate temperature control, and product pressure


3. Beer barrels are delivered at a pressure of 12 to 15 psi.The pressure controls the speed of the draw at thefaucet. Some carbon dioxide gas needs to be added to most direct draw systems to maintain a pressurebetween 14 and 16 psi.

4. These beer lines can be cooled by air or by a refrigeratedcoolant.

5. 18°F to 22°F

6. The basic system consists of a hopper, a mix-feed system,a beater, and a freezing cylinder.

7. An operator must not exceed the draw of the machine. Ifthe designed draw rate is exceeded, the product will betoo soft to stand up, and therefore unsatisfactory. Also,the operator must clean the machine on a regular basis.

8. Mix-feed systems automatically meter liquid mix into thefreezing cylinder to replace that which has been drawnoff.

9. Batch freezers are designed to produce large quantitiesof ice cream instead of a single serving like a soft-servefreezer.

10. The advantage to this design is that when a problemarises with the system, such as a refrigerant leak, onlythat system is affected. There are several disadvantagesto this design: (1) many more compressors are needed,usually resulting in higher operating costs; (2) the initialcost to install may be higher since it requires moreequipment; (3) it’s more difficult to reclaim some of theheat for use in the store, such as for space heating thestore or for heating hot water.

11. Uneven

12. 25°F with a satellite suction temperature of –33°F

13. A disadvantage of parallel systems is that a single leakcan shut down a sizable number of cases. When possi-ble, a refrigerant monitor should be used to alert theowner or service company of the problem.


14. Piping from a rack system to the individual cases is car-ried in trenches underneath the floor or overhead usinghangers.

15. The advantages of a protocol system are: it reduces the total refrigerant charge for the store; it reduces theamount of refrigerant piping needed; it decreases or elim-inates the need for EPR valves; it eliminates the need fora central area for refrigeration equipment; it lowers theinitial installation costs; it provides load matching withmultiplexed compressors.

16. They rely on an air curtain(s) to provide a barrierbetween the store’s environment and the product.

17. In the discharge air stream of the case

18. Three

19. Open display cases at low temperatures are more sensitiveto the store’s environment. Their evaporator coils tend tofreeze up more quickly, requiring longer and more frequentdefrosting. Because of this, reach-in glass door freezersare more often chosen to display frozen food productssince they’re more reliable and less troublesome at lowtemperatures.

20. The basic design of most cubed ice machines is to beginwater into a trough and pump it over an evaporator. Theevaporator will be shaped in a form to produce the shapeand size of the ice cube to be produced. The machine willsense when the correct size ice cube is formed and thendrop these ice cubes into a bin.

Unit 80

1. Pasteurizing, homogenizing, cooling and holding the mix,freezing, and then hardening

2. –20 to –30°F

3. Air films, frost and ice, scale, noncondensable gases,abnormal temperature differentials, clogged sprays, slowliquid circulation, poor air circulation, and foreign particles


4. Storage of ingredients, controlling the temperature of thedough during the mixing process, storing and freezingthe products

5. Because these food products, like all natural food prod-ucts, contain insect eggs that when not stored underrefrigerated conditions will hatch and contaminate theproduct

6. The straight dough process and the sponge doughprocess

7. Bread is frozen at temperatures between 16 and 20°Fand stored at temperatures below 0°F.

8. The ice on ice skating rinks is produced in layers.

9. The temperature of ice for ice hockey is 22°F, for figureskating 26°F, and for recreational skating 26 to 28°F.

10. Process cooling

11. –238°F

12. Dewar flasks

13. Stainless steel, aluminum alloys, and nickel steel

14. Methane, ethane, propane, pentane, and nitrogen

15. The product is placed on a conveyor belt that passesthrough a blast freezer. High-velocity low-temperature air is blown across the product so that it’s frozen as itleaves the tunnel.

16. The product is passed through a shallow liquid nitrogenbath or immersed in a low-temperature brine solution.

17. A detachable truck trailer that has a stand-alone refrig-eration system

18. Truck bodies lined with eutectic plates

19. Nitrogen and carbon dioxide flushing systems

20. This is used on fishing vessels where seawater comesinto direct contact with pipes containing refrigerant. Thecold salt water is then pumped back into the fish holds.

21. 90°F room temperature, 90°F supply water temperature,and 50°F drinking water temperature

22. Dry ice and gel packs


Unit 81

1. Perishable foods can be classified into six groups: meats,poultry, seafood, fruits, vegetables, and dairy products.

2. Microbiological: These include bacteria, molds, and fungi enzymes. They’re chemical in nature and don’tdeteriorate. Oxidation changes: These are caused byatmospheric oxygen coming in contact with the food,producing discoloration and rancidity. Surface dehydra-tion: In freezing. this is called freezer burn. Wilting: Thisapplies to vegetables that lose their crispness.

Suffocation: Certain fresh vegetables must have air.When sealed in cellophane bags, the bags must haveholes.

3. Sanitation is the most important factor in controllingbacteria.

4. Poultry spoils much faster. Poultry has a particularlyhigh level of salmonella.

5. Seafood

6. The purpose of refrigeration is to slow down the ripeningprocess so that these products can reach consumers beforespoiling.

7. These are picked green and must be ripened for market-ing. Banana rooms must be airtight. Refrigeration isprovided by using a refrigerant other than ammonia. Adesign temperature difference of 15ºF and a refrigeranttemperature of 40ºF are considered good practice.

8. Mechanical refrigeration begins to cool it even duringmilking, from 90º to 50ºF within the first hour, and from50º to 40ºF within the next hour. As more milk is added,the blended liquid must not rise above 45ºF. Milk isstored in insulated or refrigerated silo type tanks thatmaintain a 40ºF temperature. After milk is pasteurizedand homogenized, it’s again cooled in a heat exchanger(a plate or tubular unit) to 40ºF or lower, and packaged.


9. If stored improperly, the quality of butter deterioratesfrom absorption of atmospheric odors, loss of weightthrough evaporation, surface oxidation, growth ofmicroorganisms and resulting activity of enzymes, and low pH (high acid) of salted butter.

10. The ideal storage temperature range for various types ofcheese is in the range of 30–34ºF for natural cheeses and40–45ºF for processed cheeses. Maximum temperaturesrange from 45–60ºF for the natural cheeses while theprocessed cheeses may be kept on open shelves at 75ºF.

11. The temperature would need to be 45ºF and the relativehumidity 75–80%.

12. Special handling requirements

Capacity

Freezing times

Quality consideration

Yield

Appearance

First cost

Operating costs

Automation

Space availability

Upstream/downstream processes

13. By packaging in airtight containers or by waxing or glazingthe product, ice glazing is used to prevent surface dryingof fish. Fruits are often glazed with a sugar syrup to pre-vent oxidation.

14. This consists of placing the product in boiling water orsteam to kill bacteria and to stop enzyme action.

15. Cold air at high velocities is circulated over the product.The air removes heat from the product and releases it toan air refrigerant heat exchanger before being recirculated.


16. Products are placed on or between horizontal or verticalrefrigerated plates that provide efficient heat transfer andshort freezing time.

17. Cryogenic freezers utilize both convection and/or con-duction by exposing food to temperatures below –76°F inthe presence of liquid nitrogen or liquid carbon dioxiderefrigerants.

18. Products are frozen by immersion in a boiling, highlypurified refrigerant. The product is then removed and the freezing process completed in a mechanical freezer.

19. The product should be heated sufficiently to kill thesedestructive agents before refreezing.

20. Preparation, processing, and unit operations

Assembly, filling, and packaging

Cooling, freezing, and casing

Finishing: storage and shipping

21. These records should show conditions for time of day,season, on/off shift production, evaporator temperature,and equipment type/function.

22. To avoid the hazard of a potential ammonia spill to work-ers in the plant, glycol chillers are used by some plantsto circulate propylene glycol to evaporators located in theproduction areas.

23. Energy-saving measures include floating head pressurecontrols with oversized evaporative condensers coupledwith two-speed fans, single-stage refrigeration for smallareas and loads, variable speed pumps for glycol chillersystems, ice builders to compensate for peak loads, doorinfiltration protection devices, insulation, and computer-ized control systems.

24. Entering temperatures

Duration of storage

Required product temperature for maximum/minimumprotection

Uniformity of temperatures


Air movement and ventilation

Humidity

Traffic in and out of storage space

Sanitation

Light

25. The Association of Food and Drug Officials (AFDO)

Occupational Safety and Health Act (OSHA)

U.S. Department of Agriculture (USDA)

Environmental Protection Agency (EPA)

Unit 82

1. By slowing down the reproduction of bacteria andenzyme actions

2. Convection currents where cool air is heavier and fallsand warm air is lighter and rises

3. No

4. Boxes can be found that are cooling only, 35°F to 40°Ftemperature range, freezing only, –10°F to 0°F

5. The chest-type arrangement is more efficient.

6. The 2nd Law of Thermodynamics

7. In the last few passes of the condenser

8. Heat is absorbed by a refrigerant as it changes from aliquid to a gas.

9. If a hole should occur in the outer or inner shell, mois-ture would enter the space and soak into the insulation.

10. The mullion

11. The mullion heaters keep the surfaces of the mullionwarm to prevent condensation or freezing of water ontheir surfaces.

12. Refrigerator/freezer thermostats react to changes in temperature.


13. If the thermostat is kept too low, then freezing of the coilcan occur.

14. The differential is 4°F.

15. Frost forms on the freezer coil due to the coil temperaturebeing below 32°F.

16. The three main components are the defrost timer, defrostheater, and the defrost thermostat.

17. The defrost timer keeps track of the compressor runtime.

18. Dehumidifying is one effect of refrigerating that harmslettuce.

19. The crisper’s purpose is to maintain an area of higherhumidity around certain produce.

20. If the refrigerator/freezer isn’t leveled properly the doorswon’t close or open properly, water could spill out of theice-maker tray, and produce won’t sit level on theshelves.

21. The built-in gasket will pull and hold the door closed.

22. The compressor, condenser fan, and the evaporator shutoff during a call for defrost.

23. The head pressure will go up.

24. Temporary taps can be installed to access the system,then permanent taps can be installed after all the refrig-erant has been recovered from the system.

Unit 83

1. (1) Electrically diagnosing controls (switches, relays, andcontactors); and (2) electrically diagnosing loads (coils,fan motors, and compressors)

2. The voltmeter, the ammeter, and the ohmmeter

3. Voltmeter

4. Ammeter


5. Mechanical and electrical. Mechanical defects are problemsthat affect the operation of the mechanical pump insidethe compressor. Electrical defects are those problemsthat affect the electrical operation of the motor inside the compressor.

6. A technician must compare the compressor’s actualamperage draw to the amperage draw as stated by themanufacturer.

7. One possibility is the motor windings of the compressorare open, shorted, or grounded. Another possibility is thestarting components (start relay and/or capacitors) ofthe compressor are defective. The third possibility is theincorrect voltage is applied to a compressor.

8. 2%

9. Rated-load amps

10. Cylinder temperatures exceeding 300ºF will begin thebreakdown of the oil.

11. Discover why the original compressor failed.

12. To test a current relay using an ohmmeter:

1. Remove the relay from the circuit.

2. Set an ohmmeter to its lowest scale. Zero the ohmmeter (if using an analog).

3. Place the ohmmeter leads on the “L” and “M” terminals of the relay.

4. Hold relay in the upright position.

5. Read the ohmmeter.

6. If the ohmmeter reads approximately one ohm, thecoil of the relay is electrically okay.

7. If the meter reads an infinite reading, the coil is openand the relay needs to be replaced.

8. Next, place the ohmmeter leads on the “M” and “S” terminals of the relay.


9. If the ohmmeter reads an infinite resistance, the con-tacts are open—as they should be. If the meter readsa resistance, the contacts are stuck closed. The relaywill need to be replaced.

10. Try turning the relay upside down and shake. Thecontacts should be closed, showing a zero resistanceon the ohmmeter. Sometimes this test will fail evenon a good relay, but it’s worth trying.

13. 1. Remove the relay from the circuit.

2. Set an ohmmeter to high scale. Zero the ohmmeter (if using an analog).

3. Place the ohmmeter leads on the “2” and “5” terminalsof the relay.

4. If the ohmmeter reads a high resistance (approximately6,000 to 14,000 ohms), the coil of the relay is electri-cally okay. If the coil reads infinite, it is electricallyopen and the relay needs to be replaced.

5. Next, place the ohmmeter leads on the “1” and “2”terminals on the relay.

6. If the ohmmeter reads zero, the contacts are closed—as they should be. If the ohmmeter reads a highresistance or an infinite resistance, the contacts aredefective and the relay needs to be replaced.

14. To test a capacitor using an ohmmeter,

1. Remove the capacitor from the circuit.

2. Discharge capacitor with a bleed resistor or a voltmeter.

3. Set an ohmmeter to its lowest scale. Zero the ohm-meter (if using an analog).

4. Place the ohmmeter leads on the capacitor terminals.

5. Watch for one of the following indications of the con-ditions of the capacitor:

Good—Needle will swing toward zero and then slowlyreturn to infinity


Shorted—Needle will swing toward zero and remainthere

Open—Needle will stay at infinity

6. Make a second test by reversing the leads of theohmmeter.

7. If the test shows an open or shorted capacitor, repeatthe test on higher resistance scales to verify the capac-itor is truly defective. Depending on the capacitanceand the meter used, higher resistance scales mayneed to be used for an accurate test.

8. For run capacitors, place one of the ohmmeter leadson a terminal of the capacitor and one lead on thebody. If the ohmmeter reads a resistance, the capaci-tor is grounded and needs to be replaced. Next, testthe other lead of the capacitor.

15. Using water is the best method, but isn’t always practicalsince the water will need to be drained away. If watercan’t be used easily, a heat gun usually works well.

16. The method used is as follows:

Step 1—Measure the dry-bulb temperature of the air entering the condenser. (We’ll refer to this as theEAT—Entering Air Temperature).

Step 2—Measure the system’s operating suction pressure.

Step 3—Using a pressure/temperature (P/T) chart,convert the suction pressure to its equivalent satura-tion temperature.

Step 4—Determine the system’s application: low temperature, medium temperature, or high tempera-ture. A low-temperature system is one that operates at an evaporating temperature of 0°F and below. Amedium-temperature system is one that operates at an evaporating temperature of between 0°F and 25°F.A high-temperature system is one that operates at anevaporating temperature of between 25°F and 45°F.


Step 5—Using the chart below, determine the appro-priate temperature rise (TR). The TR is the differencebetween the EAT and the condensing temperature ofthe refrigerant in the condenser.

Step 6—The Condensing Temperature (CT) can then be determined by adding the EAT and the TR. CT =EAT + TR.

Step 7—Once the condensing temperature is known,its equivalent saturation pressure can be determinedusing a P/T chart. This will be the correct operatingdischarge pressure of the system.

17. The method used is as follows:

1. Determine the type of refrigerant in the system.

2. Electrically disable the compressor and allow thecondenser fan to operate.

3. Attach a temperature probe to both the dischargeline and liquid line.

4. Place a third temperature probe to measure the temperature of the air entering the condenser.

5. Connect a pressure gauge on the system to measurethe pressure of the refrigerant in the condenser.

6. When all three temperature probes (discharge line,liquid line, and air entering the condenser) read thesame temperature, record the pressure of the refrig-erant in the condenser.

7. Using a P/T chart, convert the measured pressure toits saturation temperature.

8. The converted temperature should be within a fewdegrees of the measured discharge, liquid, and airentering temperatures.

9. If the converted temperature is higher than the meas-ured temperatures by more than a few degrees, thereare non-condensables in the system that need to beremoved.


18. Some common causes of an evaporator with a low super-heat and a high suction pressure are

Oversized valve

TXV seat is leaking

Low superheat adjustment

Sensing bulb making poor thermal contact

Wrong thermostatic charge

Incorrectly located external equalizer

19. A technician should use a short refrigeration gauge onsystems containing a small amount of refrigerant.

20. Some of the various ways to search for a refrigerant leakare performing a visual inspection, using soap bubbles,using an electronic leak detector, and using refrigerantdyes.

Unit 84

1. ARI—Air Conditioning and Refrigeration Institute

ASHRAE—American Society of Heating Refrigeration and Air Conditioning Engineers

ASME—American Society of Mechanical Engineers

UL—Underwriters Laboratories

NFPA —National Fire Protection Association

2. The institute’s most important function is to establishproduct or application standards by which the memberscan design, rate, and apply to their hardware.

3. The Underwriters’ Laboratories (UL) is a testing and codeagency that specializes in the safety aspects of electricalproducts.

4. Equipment placement

Ductwork installation

Piping installation (both refrigerant and water)



Electrical connection

Evacuation and charging

Start and check

5. Ample space must be provided for air movement aroundair-cooled condensing equipment to and from the con-denser. All major components must be installed so theymay be serviced readily. When an assembly isn’t easilyaccessible for service, the cost of service becomes exces-sive. Vibration isolation must always be considered, notonly in regard to the equipment itself, but also in relationto the interconnecting piping and sheet metal ductwork.All manufacturers supply recommendations of the spacerequired; these recommendations should be followed.

6. Copper pipe and fittings should be cleaned before assem-bly. Nitrogen should be trickled through the systembefore, during, and after brazing. Plastic and other partsthat can be damaged by heat should be protected. Thejoint should be heated evenly using an oxyacetylenetorch. A brazing rod should be applied to the joint awayfrom the flame.

7. Minimum circuit ampacity

8. Maximum fuse size

9. The wire should be sized for the minimum circuit ampacity 31.5.

10. The disconnect should be sized at 115% of the minimumcircuit ampacity 1.15 ! 31.5 = 36.225. Since disconnectsizes jump from 30 amps to 60 amps, a 60 amp discon-nect will be needed.

11. The circuit breaker should be no larger than the maximumsize on the data plate 50 amps.

12. Dual element time-delay fuses or HVAC/R rated circuitbreakers

13. UL 181 rated tape and or mastic


14. Spring or rubber mounts for compressors and fans

Vibration isolation pad

Vibration eliminators in refrigerant lines

Canvas flexible connectors on duct

15. 40 feet – 25 feet = 15 feet additional line

16. 0.6 ounces (from Table 84.1) = 9 additional ouncesrequired 12 lbs 8 ounces + 9 ounces = 12 pounds 17 ounces = 13 pounds 1 ounce

17. Oil may be poured in as shown on the left.

Oil may be drawn in under the vacuum.

Oil may be forced in using an oil pump.

18. Front seated, run all the way in clockwise

19. Evacuate the lines and coil.

Unit 85

1. Routine maintenance, pre-start inspection, operationalchecks, troubleshooting

2. The initial voltage check verifies that the supplied voltageis within the manufacturer’s specifications. The comparisonof the voltage check after startup and the initial voltagecheck determines the voltage drop in the wire.

3. Combustion air, vent system integrity, CO levels in fluegas and around unit

4. Check for voltage drop in power wire, voltage drop acrosscontactor contacts, amp draw, airflow, system pressures,superheat, subcooling, temp drop across evaporator coil.

5. Higher-efficiency filters have a higher pressure drop,which can cause poor airflow.

6. Reduced operational cost and longer equipment life

7. Prevent breakdowns by replacing worn parts and makingneeded adjustments on a regular schedule.


8. Look on the unit data plate to find the nominal, minimum,and maximum unit voltage.

9. Checking the temperature rise across the indoor coil andcomparing it to a manufacturer’s performance chart

10. Power wire is too small, or poor connections at eitherend of the power wire

11. Blue

12. Shaft alignment, pulley alignment, shaft bearings, beltcondition, belt tension

13. Hard glazed sides, cracks, frays

14. Pull the lever and look for water at outlet of dischargepipe.

15. Monitoring the ultrasonic bearing sound can identifywhen bearings need lubricating and or replacing.

16. Planned maintenance is based on a schedule, while predictive maintenance is based on monitoring key performance indicators, like ultrasonic and thermalmeasurements.

17. The side where air enters, usually hidden in “A” coils

18. By paying attention to the directional arrow on the filter.The arrow points in the direction of airflow, whichshould be towards the unit.

19. Combustion air grills in the case of gas and oil appli-ances, mechanical components properly supported,ductwork insulated, suction line insulated, service clear-ance in front of the unit, drains running downhill

20. By measuring the water flow in the system, either usinga flowmeter built into the system or by measuring thepressure drop across the water pump and comparing itto a pumping performance chart


Unit 86

1. How is the equipment supposed to operate?

What is the equipment doing wrong?

What is the root cause of the problem?

What specific tests or procedures determined this?

How can this be corrected?

How much will this cost?

2. Technicians are called to work on the entire system, notan isolated part of it. Service technicians must under-stand the inter-relationship between different systemcomponents and be aware of the effect one process hason the rest of the system.

3. Low evaporator airflow can cause low system pressures.

4. Understanding system operational sequence

Preliminary system inspection

Collecting operational data

Recognizing what’s operating incorrectly

Testing to isolate the cause

Recommending corrective action

5. 1. Check the thermostat setting.

2. Check the air filter clean.

3. Check for adequate airflow or water flow (dependingon the type of unit).

4. Check the system operating voltage.

5. Check the system control voltage.

6. Check all major loads for shorts and grounds. Afterreplacing the fuse, check the system amp draw and compare it to the data plate rating. Finally, check theamp draw of each major load individually.


7. Check all low-voltage controls for shorts and grounds.After replacing the fuse, check the voltage output of thesecondary side of the transformer. Then monitor thatvoltage while running the system through its differentoperating cycles.

8. 1. Check line voltage to the unit.

2. Check control voltage.

3. Check voltage to the nonfunctional component.

4. Check circuit to the nonfunctional component.

9. This technique works by starting at a point where there’scorrect voltage, and moving one lead from point to pointin the circuit towards the nonfunctional load until thevoltage is lost.

10. Loose or open leads in compressor circuit

11. Inadequate GPM (water flow)

Water too hot

12. Improper main ground; Broken igniter; OR: Open ignitercircuit; Line voltage below 75 volts.

13. R control power to thermostat

Y compressor

Evaporator float switch

Liquid low-pressure switch

High-pressure switch

Anti-short cycle timer

Compressor contactor

Defrost control

Run capacitor

14. Liquid restriction

Underfeeding metering device

Low capacity compressor

15. Check to see if the vent has the correct draft.

Check for obstructions in the vent.

Check the draft pressure switch.

16. Sources of information on the system sequence of operation include the manufacturer’s installation andoperation and manuals, unit wiring diagrams, unitcharging charts, and general textbooks.

17. Sources for the current system operational data includethe homeowner, general observation, diagnostic boards,and system performance tests.

18. 164–201 psig

19. On-board diagnostics can only report issues that it hasinputs for.

20. The cost is the foremost question in the customer’s mindand the service technician needs to be able to addressthe customer’s concerns.


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