Non-return or check valves can be found in the following positions:

1. On reversible heat pump circuits, to prevent flow through expansion valves which are not in service on one cycle

2. On hot gas circuits, to prevent the gas entering another evaporator

3. Where several compressors discharge into one condenser, to prevent liquid condensing back to an idle compressor

4. Where two or more evaporators work at different pressures, to prevent suction gas flowing back to the colder ones

Posted in Refrigeration and Air Conditioning