During the heating cycle, the outdoor coil operates as which component?

During the heating cycle, the outdoor coil functions as the evaporator. In this process, the heat pump absorbs heat from the outside air, even in cold temperatures, and transfers it indoors. The refrigerant in the outdoor coil evaporates as it absorbs heat, changing from a liquid to a gas. This phase change takes place as the refrigerant's temperature drops below the outside air temperature, allowing it to absorb heat efficiently.

The role of the outdoor coil as the evaporator is crucial for the heat pump's operation, enabling it to leverage environmental thermal energy for heating purposes. Understanding this function is essential for troubleshooting and optimizing heat pump systems. In contrast, the other components—such as the condenser, compressor, and reversing valve—have distinct roles in the overall operation of the heat pump system.