Refrigeration and air conditioning compressors are vapor compressors, meaning they are designed to compress refrigerant vapor, not liquid refrigerant. Liquids cannot be compressed, which is why liquid refrigerant is one of the worst enemies of a compressor. The compressor is often referred to as the heart of the refrigeration system. Without the compressor, refrigerant could not reach other system components to perform its heat transfer functions.
Reciprocating compressors, along with many other types of compressors, cannot handle liquid refrigerant coming into them. Serious mechanical damage will occur to the compressor’s valve structure and drive train when liquid refrigerant enters the compressor’s cylinders or end bell. If the liquid refrigerant doesn’t do direct damage to the valve structures, it will do indirect damage to the internal drive components of the compressor when it dilutes the crankcase’s oil and degrades its lubricity.