The King Valve is installed on which part of an AC system?

• A. Suction line
• B. Liquid line / outlet of receiver
• C. Discharge line
• D. Thermostat line

Answer: (B)

The King valve is a one-way check valve placed in the liquid line, typically right after the receiver. Its job is to prevent reverse flow of liquid refrigerant and refrigerant migration when the system cycles off, which helps protect the compressor from liquid slugging and keeps the liquid moving in the correct direction toward the metering device. The liquid line is the path from the receiver to the expansion device, so this is where a backflow-preventing valve belongs. The suction line carries vapor back to the compressor, the discharge line carries high-pressure gas to the condenser, and the thermostat line is an electrical control line, not a flow-control valve.