March 2017 Tech Challenge


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An R-410A rooftop system with a fixed orifice has a customer complaint of insufficient cooling. The symptoms confirm a warm building and the blower and compressor appears to be running all of the time. 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. 243 deg. F.
Condensing Press./Temp. 431 psig / 122 deg. F.
Condensing Outlet  100 deg. F.
Condenser Sub cooling 22 deg. F.
Condenser Split 42 deg. F.
Entering Feed Device Temp. 85 deg. F.
Evaporator Press./Temp. 143 psig / 50 deg. F.
Evaporator Outlet Temp. 59 deg. F.
Evaporator Superheat 9 deg. F.
Compressor Inlet Temp. 65 deg. F.
Total S. H. 15 deg. F.
Ambient Temp. 80 deg. F.
Room/Box Temp. 82 deg. F
Compressor Volts 240 V.
Compressor Amp. Draw  High

Looking for the answer? Check hvac-blog.acca.org on April 28, 2017 for the answer to this issue’s Tech Challenge.


Posted In: ACCA Now, Tech Challenge

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