In a reverse-cycle system, what component changes refrigerant flow from heating to cooling?

In a reverse-cycle system, the component responsible for changing the refrigerant flow between heating and cooling modes is the four-way valve. This valve plays a crucial role in directing the flow of refrigerant to either pull heat from the inside of a building (when in cooling mode) or to transfer heat from outdoors to the inside (when in heating mode). By reversing the direction of the refrigerant flow, the four-way valve allows the heat pump to efficiently switch between its heating and cooling functions, making it essential for the system's versatility.

While the compressor, condenser, and check valves are important components in a refrigerant system, they do not have the specific function of reversing the refrigerant flow. The compressor circulates the refrigerant, the condenser removes heat during the cooling process, and check valves are used to ensure that refrigerant flows in one direction, but none of these components can change the direction of the refrigerant flow like the four-way valve can.