In a heat pump designed for both heating and cooling, which device changes the flow of the refrigerant for each mode?

• A. Thermostat
• B. Condenser fan
• C. Expansion valve
• D. Reversing valve

Answer: (D)

The device that changes the flow path of the refrigerant to switch between heating and cooling is the reversing valve. This four-way valve redirects the high-pressure refrigerant after it leaves the compressor so the indoor and outdoor coils swap roles depending on mode. In cooling, the indoor coil acts as the evaporator (absorbs heat from the room) and the outdoor coil acts as the condenser (releases heat outside). In heating, the valve reverses flow so the outdoor coil becomes the evaporator (absorbs heat from outside) and the indoor coil becomes the condenser (releases heat into the room). The thermostat controls on/off and temperature settings, not the refrigerant path, and the expansion valve merely meters refrigerant into the evaporator, not switch coils.