Tech Challenge – July 2018


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A rooftop utilizing R-410A with a fixed orifice metering device has a customer complaint of “no cooling.” The symptoms 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. 225 deg. F
Condensing Press./Temp. 292 psig / 94 deg. F.
Condensing Outlet 88 deg. F.
Condenser Sub cooling 6 deg. F.
Condenser Split 7 deg. F.
Entering Feed Device Temp. 88 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. 87 deg. F.
Room/Box Temp.34 80 deg. F
Compressor Volts 240 V.
Compressor Amp. Draw Low

Looking for the Answer: Check hvac-blog.acca.org on August 31, 2018, for the answer to this issue’s Tech Challenge.


Posted In: ACCA Now, Tech Challenge

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