Modern condensing units, low-pressure control switches are largely replaced by thermostatic-control switches. Thermostatic consists of three main parts: a bulb, capillary tubes, and a power element or switch. Lamp is attached to the evaporator in a manner that ensures contact with the evaporator. He may contain volatile liquids such as refrigerant. Lamp is connected to a source element with a small capillary tube (see Fig. 14-13).
The work of the bellows is provided by the temperature change. Or thermostatic switch management, such as increased temperature of the evaporator, bulb temperature also increases. This raises the pressure thermostatic-liquid pairs. This, in turn, causes bellows expand and intensify the electric contact. Contact closes the circuit of the engine, and the engine and compressor will start to work. As evaporator temperature decreases and the lamp becomes colder and the pressure is reduced to the point where bellows contracts enough to open the electrical contacts, so turning off the motor circuits. Thus, the condensing unit is fully automated. Thus, it is able to produce as much cold required to meet any normal operating condition.