May 2017 Tech Challenge - IE3: Business Tools for HVAC & Plumbing Contractors  

May 2017 Tech Challenge

A commercial rooftop utilizing R-410A with a TXV feed device (and receiver) has a customer complaint of “insufficient cooling.” The symptoms confirm inadequate cooling and the compressor appears to be running all of the time and the thermostat is not 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. 236 deg. F.
Condensing Press./Temp. 442 psig / 124 deg. F.
Condensing Outlet  112 deg. F.
Condenser Sub cooling 12 deg. F.
Condenser Split 36 deg. F.
Entering Feed Device Temp. 89 deg. F.
Evaporator Press./Temp. 125 psig / 43 deg. F.
Evaporator Outlet Temp. 52 deg. F.
Evaporator Superheat 11 deg. F.
Compressor Inlet Temp. 68 deg. F.
Total S. H.  25 deg. F.
Ambient Temp. 88 deg. F.
Room/Box Temp. 78 deg. F
Compressor Volts 240 V.
Compressor Amp. Draw  High

Looking for the answer? Check back on June 29, 2017 for the answer.


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