November 2016 Tech Challenge


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A rooftop system utilizing R-22 with a fixed orifice metering device has a manager’s complaint of “no cooling.” The symptoms at the store confirm that the thermostat is not satisfied and the condensing unit and blower are running continuously. 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. 230 deg. F.
Condensing Press./Temp. 390 psig / 115 deg. F.
Condensing Outlet Temp. 88 deg. F.
Condenser Sub cooling 27 deg. F.
Condenser Split 35 deg. F.
Entering Feed Device Temp. 82 deg. F.
Evaporator Press./Temp. 129 psig / 45 deg. F.
Evaporator Outlet Temp. 50 deg. F.
Evaporator Superheat 5 deg. F.
Compressor Inlet Temp. 66 deg. F.
Total S. H. 25 Deg. F.
Ambient Temp. 80 deg. F.
Room/Box Temp. 84 deg. F
Compressor Volts 240 V.
Compressor Amp. Draw High

Looking for the answer? Check hvac-blog.acca.org on January 29, 2016 for the answer to this issue’s Tech Challenge.


Posted In: ACCA Now, Tech Challenge

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