In a pump-down system, where is the solenoid valve located?

In a pump-down system, where is the solenoid valve located?

• A. Before the metering device
• B. In the suction line
• C. After the condenser
• D. In the discharge line

Answer: (A)

The pump-down control works by isolating the evaporator from the rest of the system so the compressor can pull refrigerant back into the receiver, leaving the evaporator with minimal liquid. To do this effectively, the solenoid valve is placed in the liquid line between the condenser and the metering device—i.e., before the metering device. When this valve closes, no liquid refrigerant can reach the metering device and evaporator, so the compressor pumps the liquid back into the receiver, achieving a pump-down. Placing the valve in other locations (like the suction line or discharge line) wouldn’t trap the liquid in the evaporator in the same way or would interfere with other parts of the cycle.

The pump-down control works by isolating the evaporator from the rest of the system so the compressor can pull refrigerant back into the receiver, leaving the evaporator with minimal liquid. To do this effectively, the solenoid valve is placed in the liquid line between the condenser and the metering device—i.e., before the metering device. When this valve closes, no liquid refrigerant can reach the metering device and evaporator, so the compressor pumps the liquid back into the receiver, achieving a pump-down. Placing the valve in other locations (like the suction line or discharge line) wouldn’t trap the liquid in the evaporator in the same way or would interfere with other parts of the cycle.