Refrigeration systems for cars air conditioning usually comprise a compressor, a condenser, a receiver for containing a liquefied refrigeration fluid, and an evaporator serially connected to each other and between the outlet side and the intake side of the same refrigeration compressor, as well as control means to avoid compressor overheating.
The presently existing control systems for avoiding the overheating of refrigeration compressors, usually comprise thermostatically actuated safety devices for sensing the temperature of the compressor allowing the circulation of a flow of refrigerant for cooling the compressor. According to the operation mode, at a preset temperature the thermostatic control device starts allowing a flow of refrigerant from the fluid receiver to the intake side of the compressor to avoid overheating; nevertheless a thermostatic control system does not save the compressor from overheating as soon as a leakage of gas in the refrigeration circuit will not allow the liquefied refrigerant in the receiver to be sufficiently fed to the compressor and to the same thermostatic control device. In this event, the compressor will be no longer cooled and overheating will start. Because of that, the thermostatic control device totally opens and a flow of refrigerant in gas state will not cools the compressor which therefore will break-down. For this reason of for cost reasons, the thermally controlled safety devices and similar devices electronically controlled devices, are complex all involving relevant costs and are not used in economical refrigerating systems such as in air conditioning of cars, vehicles, boats and the like.