Tech Challenge – May 2012


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An installed split A/C system utilizing R-410A with a fixed orifice metering device has a customer complaint of “no cooling.” The symptoms at the customer’s home confirm that the thermostat is not satisfied and the condensing unit and blower are running continuously. The system is one of the first few R-410A manufactured systems and is about 12 to 14 years old. The system has only had maintenance, and no service issues. What are the “possible causes” (there is only one problem intended) with the following measured conditions on this field service check sheet?

Field Service Check Sheet

Compressor Discharge Temp. 225 deg. F.
Condensing Press./Temp. 295 psig / 95 deg. F.
Condensing Outlet Temp. 87 deg. F.
Condenser Sub cooling 9 deg. F.
Condenser Split 11 deg. F.
Entering Feed Device Temp. 86 deg. F.
Evaporator Press./Temp. 145 psig / 51 deg. F.
Evaporator Outlet Temp. 65 deg. F.
Evaporator Superheat 14 deg. F.
Compressor Inlet Temp. 76 deg. F.
Total S. H. 25 Deg. F.
Ambient Temp. 85 deg. F.
Room/Box Temp. 80 deg. F.
Compressor Volts 240 V.
Compressor Amp. Draw Low

Share this challenge with your technicans to find out if they can figure out the problem. You can also share your thoughts here by posting them in the comments section below. Check back after July 1 for the correct solution.

And the answer is…

The possible causes center on an “Inefficient Compressor.” The high discharge temperature is caused by the re-compression, the pressures are closer to each other (low condensing and high evaporator), low splits and low amps. The system is flowing very little refrigerant, has a high evaporator temperature and not picking up much heat.


Posted In: ACCA Now, Tech Challenge

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