A suction line check valve is sometimes used on the ________ evaporators on multiple refrigeration systems.

• A. Coldest
• B. Hottest
• C. Most efficient
• D. All evaporators

Answer: (A)

The idea behind a suction line check valve is to stop backflow in a shared suction line and to protect the compressor from liquid return or floodback in a multi-evaporator system. In systems with several evaporators tied to one suction line, the evaporator that runs the coldest is most prone to having liquid refrigerant present in its lines. If other evaporators cycle or if the system is shutting down, that liquid can try to migrate backward toward the compressor. Placing a suction line check valve on the coldest evaporator’s line isolates that leg and prevents reverse flow, so only vapor is drawn toward the compressor. This reduces the risk of liquid slugging and compressor damage. The other choices don’t have the same risk profile, and applying the valve to all evaporators isn’t necessary.