Honeywell TRUEDRY DH150 - Defrost Thermostat

TrueDRY DH150
15 69-2271EFS—01
Replacing a Burned Out Compressor
Therefrigerantandoilmixtureinacompressorischemicallyverystableundernormaloperatingconditions.
However,whenanelectricalshortoccursinthecompressormotor,theresultinghightemperaturearccausesapor-
tionoftherefrigerantoilmixturetobreakdownintocarbonaceoussludge,averycorrosiveacid,andwater.These
contaminantsmustbecarefullyremovedotherwiseevensmallresidueswillattackreplacementcompressormotors
and cause failures.
Thefollowingprocedureiseffectiveonlyifthesystemismonitoredafterreplacingthecompressortoinsurethatthe
clean up was complete.
1. Thisprocedureassumesthatthepreviouslylistedcompressormotorcircuittestsrevealedashortedoropen
winding.
2. Removeandproperlydisposeofthesystemcharge.DONOTventtherefrigerantorallowittocontactyoureyes
orskin.
3. Removetheburnedoutcompressor.Userubberglovesifthereisanypossibilityofcontactingtheoilorsludge.
4. Tofacilitatesubsequentsteps,determinethetypeofburnoutthatoccurred.Ifthedischargelineshowsno
evidenceofsludgeandthesuctionlineisalsocleanorperhapshassomelightcarbondeposits,theburnout
occurred while the compressor was not rotating. Contaminants are therefore largely confined to the compressor
housing.Asingleinstallationofliquidandsuctionlinefilter/drierswillprobablycleanupthesystem.
Ifsludgeisevidentinthedischargeline,itwilllikelybefoundinthesuctionline.Thisindicatesthecompressor
burnedoutwillrunning.Sludgeandacidhavebeenpumpedthroughoutthesystem.Severalchangesoftheliquid
andsuctionfilter/drierswillprobablybenecessarytocleansethesystem.
5. Correctthesystemfaultthatcausedtheburnout.Consultthefactoryforadvice.
6. Installthereplacementcompressorwithanewcapacitorandanoversizedliquidlinefilter.
Inarunningburnout,installanoversizedsuctionlinefilter/drierbetweentheaccumulatorandcompressor.
Thoroughlyflushtheaccumulatorwithrefrigeranttoremovealltrappedsludgeandtopreventtheoilholefrom
becomingplugged.Astandingburnoutdoesnotrequireasuctionlinefilter/drier.
7. Evacuatethesystemwithagoodvacuumpumpandaccuratevacuumgauge.Leavethepumponthesystem
for at least an hour.
8. Operatethesystemforashortperiodoftime,monitoringthesuctionpressuretodeterminethatthesuction
filterisnotbecomingplugged.Replacethesuctionfilter/drierifpressuredropoccurs.Ifasevererunningburn
outhasoccurred,severalfilter/driersmayhavetobereplacedtoremovealloftheacidandmoisture.
NOTE:NEVERusethecompressortoevacuatethesystemoranypartofit.
Replacing a Compressor, Non-Burnout
Removetherefrigerantfromthesystem.Replacethecompressorandliquidlinefilter/drier.Chargethesystemto50
PSIGandcheckforleaks.Removethechargeandweighintherefrigerantquantitylistedonthenameplate.Operate
the system to verify performance.
Defrost Thermostat
Thedefrostthermostatisattachedtotherefrigerantsuctiontubebetweentheaccumulatorandthecompressor.It
willautomaticallyshutthecompressoroffifthelowsiderefrigeranttemperaturedropsduetoexcessivefrostfor-
mationontheevaporatorcoil.Theimpellerfanwillcontinuetorun,causingairtoflowthroughtheevaporatorcoil
andmelttheice.Whentheicehasmelted,theevaporatortemperaturewillriseandthethermostatwillrestartthe
compressor.
Troubleshooting