Regarding heat pumps, which valve is used to change from heat to cool?

• A. Reversing valve
• B. Globe valve
• C. Check valve
• D. Solenoid valve

Answer: (A)

A heat pump switches between heating and cooling by reversing the direction of the refrigerant flow with a reversing valve. This four‑way valve, controlled by the thermostat, swaps which coil acts as the evaporator and which acts as the condenser. In heating mode, the outdoor coil becomes the condenser and the indoor coil the evaporator, pulling heat from outside and delivering it indoors. In cooling mode, the roles reverse, removing heat from indoors and releasing it outside. The other valves listed serve different purposes—globe valves regulate flow, check valves prevent backflow, and solenoid valves provide on/off or divert control in parts of the system—but they don’t switch the entire cycle direction. So the valve that changes from heat to cool is the reversing valve.