The defrost function protects the compressor from liquid shock and guarantees performance to the user. In the Cassette equipment the defrost function is based on the defrost thermostat.
When the system is running reverse cycle (for heating), and the
temperature in the external heat exchanger is above -4 ° C, the thermostat maintains
the reversing valve coil and the external fan motor energized. When the temperature reaches -4 ° C, the deicing thermostat opens and the valve reverses causing the hot gas to pass through the external heat exchanger in the same way as it switches off the external fan motor. In this way the external exchanger will be heated and the ice formed will melt. When it reaches 18 ° C, the coil and fan motor are energized again.
