Where do you install the King Valve on an AC system?

• A. Suction line
• B. Liquid line / outlet of the receiver
• C. Discharge line from the compressor
• D. Refrigerant return line

Answer: (B)

A King valve is a one-way valve used to control liquid refrigerant flow, so it must be placed in the liquid line to prevent backflow. Installing it right after the receiver outlet ensures that, during shutdown or pump-down, liquid refrigerant cannot migrate back toward the compressor. This protects the compressor from liquid slugging and allows the system to be isolated for service. The other lines (suction, discharge, or refrigerant return) carry gas/vapor or serve different functions, so a one-way valve in those paths wouldn’t provide the intended backflow control. Therefore, the proper location is in the liquid line, at or just after the outlet of the receiver.