A freezer utilizing R-402A with a TXV metering device (and receiver) has a customer complaint of “warm case.” The symptoms at the store confirm that the case that normally operates about 0 degrees is 34 degrees and the condensing unit is running continuously. What are the “possible causes” (note: there is only one problem intended) with the following measured conditions on this field service check sheet?et?
Field Service Check Sheet
Compressor Discharge Temp. | 240 deg. F. |
Condensing Press./Temp. | 204 psig / 90 deg. F. |
Condensing Outlet | 87 deg. F. |
Condenser Sub cooling | 3 deg. F. |
Condenser Split | 5 deg. F. |
Entering Feed Device Temp. | 86 deg. F. |
Evaporator Press./Temp. | 48 psig / 14 deg. F. |
Evaporator Outlet Temp. | 36 deg. F. |
Evaporator Superheat | 22 deg. F. |
Compressor Inlet Temp. | 54 deg. F. |
Total S. H. | 40 deg. F. |
Ambient Temp. | 85 deg. F. |
Room/Box Temp.34 | deg. F |
Compressor Volts | 240 V. |
Compressor Amp. Draw | Low |
And the answer is…The possible cause appears to be an inefficient compressor. The head pressure is lower and the suction pressure is higher than normal with a very high discharge temperature caused by the recompression of gases. The TXV is wide open, but there is very low refrigerant flow causing maximum subcooling (to with-in 2 deg. of ambient) and high superheat. The amps are low because the compressor isn’t working. A compressor efficiency check per manufacturers specifications needs to be accomplished.