The principle analysis and inspection of pressure switch

Pressure switch is in refrigeration system over-voltage or under-voltage protection compressor is not damaged. According to the function can be divided into high pressure or low pressure switch, they used to control the condensing and evaporating pressure respectively. When high pressure more than ratings in the refrigeration system, and low pressure is lower than the rated value, contact action makes the compressor stop working.

(1) high voltage relay. The normally closed type pressure switch contacts. Air conditioner contact connected during normal operation, when the condensing pressure than normal, by normally closed contact is a normally open, thus make the system automatically disconnect compressor control circuit protection. High voltage relay disconnect in 24 ~ 27 kg pressure, back pressure is 21 kg. Commonly used models with some model type, high voltage relay disconnect and connect the pressure is not a constant value, disconnection of simple cold and heat pump pressure are also different, the pressure relay control used in the air conditioner manufacturers is also different.

Pressure switch contact type. Pressure relay according to the different control functions, can be divided into the normally open type pressure relays, pressure relay two normally closed type, and therefore should pay attention to maintenance.

(2) low pressure switch. Low voltage relay principle the same as the high voltage relay, it through the brass with low pressure in the refrigeration system pipe connection. When the system is evaporating pressure is too low, protects the compressor is not damaged. Low voltage relay disconnect pressure for 1 ~ 2 kg, back pressure is 2 ~ 3 kg.

Above two kinds of pressure switch is also known as stationary pressure relay.

(3) high and low voltage relay. High and low voltage relay due to the mechanical structure, have double protection function, it is in shape and discrete pressure dint, relay have obvious difference. Its characteristic is to control the pressure can be adjusted and physically big, is mainly used for large air conditioner control circuit.

(4) pressure switch testing. Pressure relay common faults, high pressure or low pressure system did not exceed the specified value, while pressure relay misoperation; Pressure relay contact point contact bad or damaged. The fault block with multimeter electricity are easy to determine. When testing by measuring the pressure value of the refrigeration system operation state to determine, such as cooling system pressure is normal, the pressure relay contact disconnect, pressure relay is damaged.