What can liquid slugging of the compressor be primarily caused by?

Liquid slugging of the compressor primarily occurs when liquid refrigerant enters the compressor's cylinder, which is designed to compress gas, not liquid. One of the key contributors to this issue is the hunting of the thermal expansion valve (TEV). When a TEV hunts, it can cause erratic refrigerant flow, allowing liquid refrigerant to build up and then suddenly flood the compressor. This flooding results in liquid slugging, which can lead to significant damage to the compressor as it tries to compress a liquid rather than a gaseous refrigerant.

In contrast, low oil levels, high superheat settings, and high ambient temperatures do not directly cause liquid slugging. Low oil can affect lubrication, but it does not impact the phase of the refrigerant entering the compressor. A high superheat setting typically indicates that the vapor has a sufficient amount of heat, which would prevent liquid flooding. High ambient temperatures may increase system pressures but are less likely to cause the immediate slugging effect seen with a malfunctioning TEV. Thus, the hunting of the TEV is a critical factor in enabling conditions for liquid slugging to occur.