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Tech Challenge September 2019 – Answer

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split A/C system utilizing R-22 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.  274 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.  72 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

ANSWER: The problem appears to be a restricted air flow over the condenser caused from a dirty condenser, diverted air flow or condenser fan issue. The condensing pressure/temperature, and condenser split are high to expel the heat gained in the evaporator, superheat and compressor. The high compression ratio is causing recompression, high discharge temperatures and high amperage. The subcooling and superheat are high to normal because the TXV is attempting to maintain a constant S.H. with a lower refrigerant flow caused by the higher compression ratio. 

Posted In: Tech Challenge

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