Symptom Possible Cause
Corrective Action
Low
discharge
pressure
*OTVGmDJFOUSFGSJHFSBOUDIBSHF
$IFDLTVCDPPMJOHDIFDLGPSMFBL3FQBJSMFBLBOEBEE
refrigerant.
%FGFDUJWFPSJNQSPQFSMZBEKVTUFE
expansion valve.
$IFDLTVQFSIFBUJOHBOEBEKVTUUIFSNBMFYQBOTJPOWBMWF
Low suction pressure.
4FFiMPXTVDUJPOQSFTTVSFw
'BVMUZDPOEFOTFSUFNQFSBUVSFDPOUSPMT
$POEFOTJOHGBODZDMFTXJUDI
$IFDLDPOEFOTFSDPOUSPMTBOESFTFUUPPCUBJOEFTJSFE
condensing temperature.
$PNQSFTTPS
TIPSUDZDMFT
Thermostat location or controls
malfunction.
$IFDLUIFSNPTUBUDIFDLIFBUBOUJDJQBUPSTFUUJOH
*NQSPQFSSFGSJHFSBOUDIBSHF
$IFDLTVCDPPMJOHWFSJGZTVQFSIFBU
Defective high or low pressure control.
$IFDLIJHIPSMPXQSFTTVSFTXJUDI
1PPSBJSEJTUSJCVUJPO
$IFDLEVDUXPSLGPSSFDJSDVMBUJOH
)JHIEJTDIBSHFQSFTTVSF
4FFiIJHIEJTDIBSHFQSFTTVSFw
-PXBJSnPXBUFWBQPSBUPS T
$IFDLCMPXFSPQFSBUJPOBOEBJSTUSFBNSFTUSJDUJPOT
*ODPSSFDUVOJUTFMFDUJPO PWFSTJ[FE
$POUBDUGBDUPSZ
$PNQSFTTPS
loses oil
3FGSJHFSBOUMFBL
$IFDLTZTUFNGPSMFBLT3FQBJSMFBLTBOEBEESFGSJHFSBOU
4IPSUDZDMJOH
$IFDLMPXQSFTTVSFDPOUSPMTFUUJOHT
3FGSJHFSBOUnPPECBDL
$IFDLUIFSNBMFYQBOTJPOWBMWFTFUUJOH$IFDLGPS
SFGSJHFSBOUPWFSDIBSHF$IFDLDSBOLDBTFIFBUFS
operation.
3FIFBUnVTIDZDMFJOBEFRVBUF
$POUBDUGBDUPSZ
Not enough
cooling
PSMBDLPG
cooling
Refrigeration undercharged.
$IFDLTVCDPPMJOH"EKVTUDIBSHFJGOFDFTTBSZ
%JSUZmMUFSPSFWBQPSBUPSDPJM
$IFDLmMUFSDPJMBOEBJSnPX
%JSUZPSDMPHHFEDPOEFOTFSDPJM
$IFDLDPJMBOEBJSnPX
"JSPSPUIFSOPODPOEFOTBCMFTJO
TZTUFN
$IFDLFRVBMJ[FEIJHITJEFQSFTTVSFXJUIFRVJWBMFOU
outdoor temperature.
Restriction in suction and liquid line.
$IFDLGPSSFTUSJDUJPOTJOSFGSJHFSBOUDJSDVJU
$POUSPMDPOUBDUTTUVDL
$IFDLXJSJOH
&YDFTTJWFMPBE
"EENPSFFRVJQNFOUPSSFEVDFSPPNMPBE
Liquid line
is frosted
or wet
Restriction in liquid line.
$MFBSSFTUSJDUJPOVQTUSFBNPGQPJOUPGGSPTUJOH
4VDUJPOMJOF
is frosting
*OTVGmDJFOUFWBQPSBUPSBJSnPX
$IFDLBJSnPXDIFDLmMUFSTDIFDL7'%DPOUSPMTJHOBMGPS
proper operation.
.BMGVODUJPOJOHPSEFGFDUJWFFYQBOTJPO
valve.
$IFDLCVMCPGUIFSNBMFYQBOTJPOWBMWF
Frost on
evaporator
coil
)PUHBTCZQBTTWBMWFOPUGVODUJPOJOH
QSPQFSMZ
$IFDLWBMWF*GEFGFDUJWFSFQMBDF
.BOVBMIPUHBTCZQBTTWBMWFDMPTFE
Open valve.
-PXMPBEPSBJSnPX
*ODSFBTFBJSnPXDIFDLmMUFST
Troubleshooting – Refrigeration Circuit
Always have a completed Pre-Start-Up Checklist and Start-Up Checklist prior to requesting parts or service
information.
25
Packaged Rooftop Ventilator
®
