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What are you using the compressed air for?Thetypeofworkyoudoisprobablythemost

importantfactorindeterminingcompressorsize.Doyouintendtouseairsixhoursperday/

fivedaysaweek,oronlyoccasionally?Areyourdemandsforcompressedairrelativelyconstant

duringtheday,ordotheyvarywidely?Purchaseacompressordesignedforadutycyclewhich

equalsorexceedsspecifiedrequirement.

Where will the compressor be located? Outdoorapplicationsrequirespecialprotectionagainst

waterandfreezing.Indoors,sufficientventilationiscrucialforsuccessfuloperationsincemost

reciprocatingcompressorsareaircooled.Don’tputthecompressorinacloset,forexample.

Placethecompressoratleastthreefeetfromthewalltoensureproperairflowandbesurethe

installationsiteissufficientlyventilatedtohandletheheatgeneratedbythecompressorduring

operation..

How much pressure (psi) do you require? Thepsi,orpoundspersquareinch,capabilityofa

compressormustmatchorexceedthepsirequirementofyourhungriestairtoolsandpneumatic

equipment.Checkthemanufacturer’sspecificationsandpressurerequirementforallyour

equipment.Thepressurealsodetermineswhethertheunitshouldbeasingle-stage(max135psi)

oratwo-stage(max175psi)compressor.

How much air flow (cfm) do you require? Cubicfeetperminuteorcfmisameasureofairflowthecompressorcancreate.CFMisstatedintwodifferentforms,pistondisplacement(PD)oractualcubicfeetperminute(acfm).Alwaysconsidertheacfmasitreflectstheamountofusableairavailableforwork.Readthefineprintandmakesureyouunderstandwhetherthecfmratingis“pistondisplacement”or“actualdeliveredair”ataspecifiedpsi.

What motor horsepower do you require? Horsepowerisdirectlyproportionaltocfmrating

ofacompressor;typically,thehigherthehorsepowerthemoreair(cfm)thecompressorcan

produce.Don’trelysolelyonhorsepowerorattempttobuythehighesthorsepowercompressor

youcanafford.Letyourcfmandpsirequirementsdeterminehorsepowerforyou.Bevery

carefulwiththecompressorsthatclaimhighhorsepowerratingwithlowairflowperformance,this

oftenindicatesan“occasional-use”aircompressor.Theseproductsaredesignedwiththemotor

operatingatmaximumspeed,whichtypicallyresultsinamotorthatwillrunhotwithseverely

shortenedlifespan.

10 Steps to Selecting an Air Compressor

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10 Steps to Selecting an Air Compressor (continued)

What size and type of air tank do you require?Airtankshelpeliminatepulsationinthe

airlineandprovidestoragewhendemandforairexceedsthecapacityofthecompressor.The

largerthetank,themorepressurizedairisavailableforoutput.Thesmallerthetank,themore

thecompressorhastoworktokeepupwiththedemand.Decideifyourapplicationrequires

averticalorhorizontaltank;thisisdeterminedbythephysicallocationofthecompressorand

one’spersonalpreference.Verticalcompressorshaveasmallerfootprintthanahorizontaldesign;

verticaltanksareonlyavailableonmodelsratedupto10horsepower.

What compressor features should you consider? Lookforthefollowingfeaturestosuitmore

demandingapplications:

•100%cast-ironconstructiondesignedforreliabilityanddurability.

•Minimalmovingpartsreducesmaintenancecostandserviceintervals.

•Splashlubricationprovidessimple,reliabledesignreducinginitialpurchaseprice

•Stainlesssteelfingervalveseliminatecorrosionwhileinsuringlongservicelife.

•One-piececonnectingrodseliminateinternaladjustment.

•Oilmonitoringdevicetopreventlow-oildamage.

•Separatecastcylindersintwo-stagecompressorsforbettercoolingandextendedlife.

What are the electrical requirements of the installation? Incomingelectricalserviceisvery

importanttoidentifyandunderstandbeforepurchasingacompressor.Voltagewilldeterminethe

horsepowercapacityavailablewithoutexpensivemodifications.Thestandardvoltageforhomes

is110volts.Thisvoltagewillonlyoperatecompressorsuptothreehorsepower.IntheUnited

States,Canada,Mexicothefollowingvoltagesandphasesareavailable:

•Single-Phase1.110-1-602.208-1-603.230-1-60

•Three-Phase1.308-3-602.208-e-603.460-3-604.575-3-60

NOTE: Always have a qualified electrician review electrical requirements prior

to procuring an air compressor.

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10 Steps to Selecting an Air Compressor (continued)

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What control system do you require?Allreciprocatingaircompressorsrequireoneofthe

threecontrolsystemsinordertoregulateoperationinaccordancewithairdemand:

•Start/StopControlisusedforapplicationswhereairisnotrequiredcontinually,

allowingthecompressorsufficientcoolingtime.Whensystempressurefallsbelowtheset

start-uppressure,thecompressorwillautomaticallystart.Whenthecut-offpressureis

reached,thecompressorwillautomaticallyshut-offandwillnotstartagainuntilthesystem

pressurefallsbelowtheminimumstartpressure.

•ConstantSpeedControlkeepsthecompressorfromexcessivelystartingand

stopping.Aswithstart/stopcontrol,ithasaminimumstartpressureandamaximumcut-

offpressure.Thisfeaturepreventsprematuremotorfailureandminimizesoperatingcosts

associatedwithhighamp-draw.Here’saruleofthumb:ifthecompressorstartsmorethansix

toeighttimesperhour,youshouldoperateconstantspeedcontrol.Ifthecompressorstarts

lessthansixtimesperhour,start/stopcontrolisrecommended.

•DualControlallowsthecompressortooperateineitherstart/stopmodeor

constantspeedcontrolmodebyadjustingthecompressorauxiliaryvalve.Thiscontrolmethod

allowstheusertoeasilyadjustthecontrolmodedependentuponcompressedairusage.Know

yourrequirementsandpurchaseaccordingly!

Additional buying tips

•Allcompressorsratedfivehorsepowerandaboveshouldhaveamagneticmotorstarterfor

thermaloverloadprotection.Motorstartersaresizedaccordingtohorsepoweraswellas

byincominglinevoltage.Thestartercanbemountedtothecompressororbepositioned

remotely.Besuretochecklocalelectricalcodesandrequirementsandhaveallwiringdoneby

alicensedelectrician

•Useofproperoiliscriticaltothelong-termoperationofyourcompressor.Sincecompressors

areshippedwithoutoilinthecrankcase,besuretocheckwithyoursupplierregardingany

start-up/lubekitrequirements.Also,manymanufacturersnowofferextendedwarrantieson

thecompressorifyoupurchaseaspecificlubricant.

•Moistureisthenumberoneenemyofcompressedairsystems.Awidevarietyofmoisture

removalproductsareavailable,rangingfrominlinefiltersandmoisturedrainstoaftercoolers

andairdryer.Consultwithyourlocalcompressedairspecialistregardingyourspecificneeds.