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Tech Challenge – May 2013

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A draft beer cooler in Orlando utilizing R-134a with a TXV metering device (and receiver) has a customer complaint of “warm beer.” The symptoms at the pub confirm warm product and the condensing unit appears to be running 100% of the time, with the low pressure control not  being satisfied. What are the “possible causes” (Note: There is only one problem intended) with the following measured conditions on this field service check sheet?

Field Service Check Sheet

Compressor Discharge Temp. 200 deg. F.*
Condensing Press./Temp. 174 psig / 121 deg. F.
Condensing Outlet Temp. 111 deg. F.
Condenser Sub cooling 10 deg. F.
Condenser Split 41 deg. F.**
Entering Feed Device Temp. 86 deg. F.***
Evaporator Press./Temp. 19 psig / 18 deg. F.
Evaporator Outlet Temp. 28 deg. F.
Evaporator Superheat 10 deg. F.
Compressor Inlet Temp. 40 deg. F.
Total S. H. 22 Deg. F.
Ambient Temp. 80 deg. F.
Room/Box Temp. 45 deg. F.
Compressor Volts 240 V.
Compressor Amp. Draw High

*High Comp ratio & discharge Temp. **Very High ***Normal

And the answer is: 

The problem is a dirty/insufficient air flow over the condenser. The condensing pressure/temp. is high to expel the heat gained in the evaporator, suction line and compressor, causing a high compression ratio, a high amp draw and high discharge temperature. The Subcooling and superheat are high to near normal because the TXV is attempting to maintain a constant S.H. with a lower refrigerant flow rate caused by the higher compression ratio.

Posted In: ACCA Now, Tech Challenge

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