The indoor coil on a heat pump acts as an evaporator coil in the summer and a __________ coil in the winter.

During the winter months, the indoor coil of a heat pump functions as a condenser coil. In heating mode, the heat pump extracts heat from the outside air (even in cold temperatures) and transfers it inside. To accomplish this, the refrigerant flows through the indoor coil and releases heat into the indoor space as it condenses from a gas to a liquid. This release of heat warms the air that is circulated through the building.

In summer, the process reverses, and the indoor coil serves as an evaporator, absorbing heat from the indoor air to cool the space. The ability of a heat pump to switch between these two functions is crucial for its operation as a heating and cooling system. Understanding this dynamic is essential for anyone involved in HVAC, as it emphasizes the efficient use of refrigerant cycles within different seasonal contexts.