It is only used in cold cycle equipment to control the defrost cycle. The de-icing thermostat is NF (normally closed) type, which opens when the temperature reaches -4 ° C and closes again when it reaches 18 ° C.
When the system is running reverse cycle (for heating), and the
temperature in the external heat exchanger is above -4 ° C, the thermostat keeps the coil of the reversing valve and the motor of the external fan energized. When the temperature reaches -4ºC, the de-icing thermostat opens and the valve reverses causing the hot gas to pass through the external heat exchanger, heating it. When it reaches 18 ° C, the coil and fan motor are energized again.
