May 2016 Tech Challenge


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A rooftop utilizing R-410A with a fixed orifice has a customer complaint of insufficient cooling. The symptoms confirm a warm building and the 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. 210 deg. F.
Condensing Press./Temp. 316 psig / 100 deg. F.
Condensing Outlet Temp. 89 deg. F.
Condenser Sub cooling 11 deg. F.
Condenser Split 12 deg. F.
Entering Feed Device Temp. 49 deg. F.
Evaporator Press./Temp. 102 psig / 32 deg. F.
Evaporator Outlet Temp. 68 deg. F.
Evaporator Superheat 36 deg. F.
Compressor Inlet Temp. 78 deg. F.
Total S. H. 46 Deg. F.
Ambient Temp. 88 deg. F.
Room/Box Temp. 80 deg. F
Compressor Volts 240 V.
Compressor Amp. Draw Low

Looking for the answer? Check hvac-blog.acca.org on June 30, 2016 for the answer to this Tech Challenge.


Posted In: ACCA Now, Tech Challenge

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