The heating portion of the refrigeration cycle is similar to the
cooling cycle. By energizing the reversing valve solenoid coil,
the flow of the refrigerant is reversed. The indoor coil now
becomes the condenser coil, and the outdoor coil becomes
the evaporator coil.
The check valve at the indoor coil will open by the flow of
refrigerant letting the now condensed liquid refrigerant bypass
the indoor expansion device. The check valve at the
outdoor coil will be forced closed by the refrigerant flow,
thereby utilizing the outdoor expansion device.