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Lightening Story

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  • When LightningStrikes . .No need for a total meltdown. New irrigationtechnology keeps sprinklers safe in a storm.By Greg Parker, The Toro Co.

    Years ago, electro-mechanical controllers and hydraulicsystems were somewhat immune to lightning or electricalsurges. With the advent of solid-state control productsand electrically actuated solenoids, however, the needfor improved surge protection began to increase. Eventhen, it was assumed that a certain amount of equipmentreplacement was the inevitable result of a severe lightning

    storm. But-times have changed and so have customers'expectations.Property owners and grounds managers have tired of

    the cost and manpower required to replace solenoids, aswell as the landscape damage caused by lighting strikes.Troubleshooting lightning damage is frustrating andpainstaking, as it can show up sporadically over a long

    19 G~OUND>~l\Nct I JUlie Zaa4

  • -- WHEN LIGHTNING STRIKES

    Snlenelds featuring surqe protection technology offer protection for components beyond the controller. Photo courtesy of The Toro Co.

    period of time. The challenge for manufacturers is how tobalance the cost vs, benefit of developing surge protectionfor products within a competitive price range.Developing surge protection in control products is one

    key element; however, following recommended ground-ing techniques during installation is equally importantto ensure consistent product performance over a longerperiod of time-keeping everyone happy.

    PROPER GROUNDINGMost control products incorporate lightning protection

    devices that create a short circuit path to ground, thuslimiting the power surges caused from utility compa-nies and, most intensely, from lightning. In order forthe energy to be discharged into the ground (insteadof the equipment). a proper path to the earth must bedesigned, With a properly designed grounding circuit,the frequency and severity of damage to the electronicequipment is dramatically reduced.According to Vince Nolletti, vice president of irriga-

    tion operations for Paige Electric Co.. LP.and co-authorof the American Society ofIrrigation Consultants (ASIC)Guideline for Earth Groundi~g Electronic Equipment in Irrigation Sys-

    . terns, designing grounding circuits to protect electronicequipment is a scientific process that must be handled byqualified personnel. But it's effectiveness relies heavily oninstallation, so Nolletti recommend the following tips.Do not use cheap electrodes. Use UL-listed or NEC-

    conforming electrodes with the largest possible surfacearea. Minimize the use of ground rods because they havevery little copper surface area, detrimental inductancecharacteristics and a short service life.

    A single electrode is usually insufficient to meet Na-tional Electrical Code requirements or to achieve desiredgrounding performance. When using multiple electrodes,space them out such that each electrode has its own areain which to diSSipatel1ghtnlng energy. Mult1ple groundrod systems do a good job for electromechanical eqUip-ment, but are not very effective in protecting electronicequipment. If you use them, install them in a straight lineinstead of in a triangle formation. Using more than threeelectrodes in one circuit increases costs whtle yieldingonly incremental improvements.Try to minimize the number of bends and sharp turns

    in ground wires and electrodes. When turns are abso-lutely necessary, make sweeping bends with aminimum

    20 GR0UNI:6 MAwmlAl'U I June 2004

  • -- WHEN LIGHTNING STRIKES

    radius of 8 inches and a minimum included angle of 90degrees. This is automatically accomplished if you pullthe wire through a 1.5-inch or larger plastic sweep ell.Do not use metal fittings/conduit as they increase theinductance of the' wire.Never install grounding electrodes in the proximity

    of the wires (high voltage and remote control wire) andcable connected to the electronic equipment as this couldre-inject the lightning energy into the system. Install the

    sandy soils, you may need to install a small drip valve tomaintain adequate soil moisture levels to ensure propergrounding protection.Soil conditions can be so poor as to require soil

    amendment with ground enhancement or earth contactmaterials to improve the conductivity between the cop-per electrodes and the soil surrounding them. However,never use amendments such as salt, chemicals, coal andconcrete because they corrode and drastically reduce the

    life of the grounding electrodes.Use only 6-gauge solid bare

    copper wire to make connectionsfrom the electronic equipmentto the grounding electrodes.Smaller sizes' can be vaporizedby lightning surges, whichreach flows of over 100,000amps. Also, you should neveruse coils of bare copper wire ingrounding grids.Make connections between

    ground wires and electrodesusing the exothermal weldingprocess, otherwise known as"Cadwelds." These are kits thatallow the permanent welding ofcomponents so that they do notrequire maintenance.

    Conduct periodic mainte-nance checks on connectionsand grounding resistance witha ground megger at least once ayear to ensure product longevityand performance.

    Finally, the most importantcomponent of proper ground-ing is a circuit design based onsound engineering principles.

    (Complete gUid~lines and downloadable AUTO-CADdrawings of ground grids are available from the ASICatwww.astc.com.)

    A number of valve-in-head sprinklers feature surge protection in the solenoids. Photo courtesyofThe Taro Co.

    electrodes at least 8 feet away from the equipment andwires.Electrodes must make contact with the soil in order for

    them to function properly, and soil conductivity variesdrastically by soil type. Clay soils exhibit good conduc-tivity, which allows the grounding circuit to dissipatelightning energy very efficiently. Loose soils suck as sand,gravel and rock have very poor conducttvuy and create aserious challenge and higher maintenance costs. But soilwill nor conduct electricity without moisture. Soil needsat least 15 percent moisture content for it to conductelectricity efficiently. It is imperative that an irrigationcircuit is installed over the general area of the groundingcircuit to ensure that moisture is there all the time. In

    IMPROVEMENTS TO CONTROL PRODUCTSSurge protection features incorporated in controllers

    themselves go hand-in-hand with proper grounding.There have been several advances in this eqUipmentover the years, including adding larger metal-oxide va-ristors (MOVs) on both input and output lines. Designedto respond to the speed at which surges reach their peakcurrent, MOVs quickly clamp the initial energy spikewhen it exceeds a safe level. The larger the MOV, themore effective the response.

    ZZ GROUNfS MAlNIDJANCE I June 1UU4

  • Should a severe lightning hitoccur. a higher level of protectioncomes into play in the form ofsurge protection pills or inductors.Even though these are slower torespond than MOVs,they have theability to discharge higher levelsof energy to the ground and awayfrom the electrical components.While most control products

    employ some type of lightningprotection. these more advancedsolutions can be offered as an op-tion to meet the needs of high-riskregions of the country. of course,with additional protection comesadditional cost. But by offeringdiffering levels of protection inthe same product. users are notforced to pay for more protectionthan they need.

    THE NEXT STEPInstalling a hydraulic system

    used to be the best way to protectyalve-in-head sprinklers frombeing damaged during lightningstorms; however, this is no lon-ger the case. By enhancing thesolenoids with surge protection,system. components beyond thecontroller are being protected ineven the most high-risk areas ofthe country. Clav soils e\chihit good electricity conductivity. allowing the grounding circuit to dissipateA number of valve-in-head lightning e~ergyefficiently. PhotocourtesyofTheToroCo.

    sprinklers on the market featuresurge-protection in the solenoids.They range in protection levels, with products rated up ingly cost effective to provide high levels of surge protec-to 20.000 volts. The higher-voltage rated products offer \ .tion-even in lower-end products. .the most surge protection. Not only can these solenoids Traditionally, irrigation design consultants have beensurvive lightning seasons with no blowouts. they save facedwith the cost/value relationship of products offer-countlessman-hours, hundreds of replacement solenoids ing advanced surge protection. It has been a question ofand much aggravation-all benefits that outWeigh the protection vs, replacement. However, as product designincrease in the cost. This success also has lead,to further morphs to face everything Mother Nature throws at it,product development, including commercial-grade valves the result will continue to be greater protection for ir-designed with same advanced-technology, high-voltage rigation systems at \tlllevels. eMsolenoid.

    BENEfITS fOR CUSTOMERSWhen manufacturers are investing in new technologies

    Ithat make products better. it's the customer who wins.Technology costs are coming down. making :it increas-

    I

    Greg Parker has worked forThe Taro Co. (Riverside, Calif.)for 13 veera Heis a rggi~tgrgd landscape architect in ths state of California and a 27-vgarlendscepe indu3try veteran.

    June 1004 IGROllNDS MAINIDlANCE 13