May Tech Challenge — Answer
A split air conditioner utilizing R-410A with a TXV feed device (and receiver) has a customer complaint of “warm, no 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?
The problem with this unit appears to be a restricted TXV. The low refrigerant flow and inability to pick up heat in the evaporator is causing low discharge and suction pressures, low splits and high superheats. With low refrigerant flow and most of the refrigerant in the receiver and liquid line the subcooling is higher. The TXV is likely restricted with the formation of wax, caused by insufficient dehydration of the system during service. After the TXV is replaced or cleaned, the filter drier needs to be replaced and a deep evacuation performed that will remove all moisture and non-condensables from the system before charging and doing a system check.
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