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 by-pass 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.
The restrictor orifice used with the CA*F, CHPF coils and the AR*F air handler will be forced onto a seat when running in the cooling cycle, only allowing liquid refrigerant to pass through the orifice opening. In the heating cycle it will be forced off the seat allowing liquid to flow around the restrictor. A check valve is not required in this circuit.
HEATING CYCLE
The reversing valve on the heat pump models is energized in the cooling cycle through the “O” terminal on the room thermostat.
These models have a 24 volt reversing valve coil. When the thermostat selector switch is set in the cooling position, the “O” terminal on the thermostat is energized all the time. Care must be taken when selecting a room thermostat. Refer to the installation instructions shipped with the product for approved thermostats.