Flash gas in the liquid line: what it is and why it causes problems

Flash gas is the partial evaporation of liquid refrigerant before it reaches the expansion valve.

Possible causes

Large pressure drop, insufficient subcooling, or excessive liquid line temperature rise.

Effect

The expansion valve is not supplied with pure liquid, resulting in reduced capacity and unstable operation.

Diagnosis

Examine subcooling, temperatures, pressure, and pressure drop in the liquid line.