EngA AF Series

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AF / DCU MANUAL
IOM-52 17 of 23 Apr 13 R2
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7. Tripleevacuationorhighevacuationmethodsarebothacceptable.
8. Evacuatethesystemtoanultimatevacuumof500microns(0.5mmofmercury).
9. Checkunitrating‐plateforcorrectrefrigeranttype.Breakthevacuumwithvirginrefrigerantfroma
sealedcontainer.
10. Pressurizethesystemtoaslightpositivepressure,(oneortwopsig).ReplaceallSchraedervalve
cores.Donotallowairintothesystem.
11. Reinstallgauges,proceedtothestart‐upsectionforcharginginstructions.
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CAUTION:
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NEVERusesystemcompressorstoevacuateasystem.Operatingacompressorwhilethe
systemisunderahighvacuummaycauseinternalarcingofthewindingsand
compressorfailure.Compressordamagecausedbyhighvacuumoperationisnot
coveredbysystemwarranty.
REFRIGERANTCHARGING
Systemchargewilldependonthelengthandorientationoftheinstalledsystem.
AninitialestimateforanACsystemchargeis1lb.(0.5kg).pertonplustheweightofliquidintheliquid
line(seeTable4Weightofrefrigerantincopperlines).Ideallychargingshouldbedoneinwarmweather.
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Iftheambienttemperatureislessthandesign,restricttheairflowacrossthecondensertoincreasehead
pressureto130°F(55°C)saturateddischargetemperatureforcharging.
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1. Checkthatallmanualshutoffvalvesintherefrigerationcircuitareinthenormaloperating
position.
2. Weighinaninitialchargeofapproximately75%oftheestimatedcharge.
3. Checktoensureevaporatorsectionhasproperairflow.Checkstaticpressuredropandcompare
withdesignstatic.Checkinletairtemperaturetoevaporator.Ensurethatthereissufficientloadto
operatetheairconditioning.
4. Checkthesupplyvoltageandensurethatiswithin10%ofdesignvoltageonunitratingplate.
5. Checkcontrolvoltageatrefrigerantsolenoidvalvesandensurethatitiswithin10%ofrated
voltage.
6. Setcontrolstocallforcooling.
7. Closethesystemserviceswitch.
8. Withthesaturateddischargetemperatureapproximatelyequalto130°F(55°C),[475psig(R‐410a),
325psig(R‐407C)]Thisstepmayrequireblockingcondenserairflowtoincreaseheadpressure.
Chargesystemslowlyuntilthesightglassisclear.DONOTOVERCHARGE.
9. Checkevaporatorsuperheat.
AttachanaccuratetemperaturesensortightlytothesuctionlineattheTXbulb.Measurethe
suctionpressureatthecondensingunit.Add2psigtothispressureandconvertittothesaturated
suctiontemperatureusingtheappropriatepressuretemperaturetable.Subtractthesaturated
temperaturefromthetemperaturemeasuredattheTXbulb.Thisisthesuctionsuperheat.
Superheatshouldbebetween8°Fto14°F(5°to8°C)whenthesystemisoperatingatfullloadwith
aclearsight‐glass.
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