Compressor overheating is usually caused from high compression ratios. High compression ratios can be caused from a combination of high condensing pressures (temperatures) and low suction (evaporating) pressures.
The compressor’s superheated discharge temperature can tell the service technician what is going on inside a refrigeration or air conditioning system. The compressor’s discharge temperature is a reflection of the hottest part of a refrigeration system, and there are limits as to how hot a discharge temperature should be.
There will always be a time when the evaporator sees a light load and the TXV may lose control of its evaporator superheat due to limitations of the valve and to system instability. What do you do then?
There are times when low evaporator heat loads, just ended defrost periods, failing or misadjusted mechanical valves, or simply lack of system maintenance can cause compressor floodback. If there is no way to prevent these periods of liquid floodback to the compressor, a suction line accumulator is needed on the system.
Systematic troubleshooting using a system check sheet is still the best method for the conscientious service technician to pinpoint hard-to-find system problems. This article explores how evaporators can become oil logged, and includes symptoms with explanations of a system with an oil-logged evaporator.