The role of pressure relay in refrigeration system

The role of pressure relay in refrigeration system

In industrial refrigeration, a pressure relay is an electric switch controlled by a pressure signal. It is often used as a protection and regulating element that directly controls the start and stop of the refrigeration compressor or controls the opening and closing of certain solenoid valves. Pressure relays used in refrigeration devices are divided into low-pressure relays and high-pressure relays according to their pressure control range. There is also a combination of these two types of relays assembled in a shell and sharing an electric contact to form a combined high and low voltage relay.

　　A low-pressure relay that directly controls the starting circuit is often installed on the refrigeration compressor. It uses the compressor suction pressure as the action signal, and its function is:

　　1. When the suction pressure is too low, the compressor will automatically stop to prevent air from leaking into the system from the pipeline or shaft seal, and play a role of low pressure protection.

　　2. In a small refrigeration device, in addition to low-pressure protection, the compressor can also be automatically started and stopped according to the set suction pressure to keep the cold storage temperature stable and play a role in temperature adjustment. In large and medium-sized devices, because the compressor has a relatively large starting current, a low-voltage relay is often not used to automatically start the compressor, so it only serves as a low-voltage protection.

In addition, some piston compressors are also equipped with a low-pressure relay that controls the electromagnetic width of the automatic energy adjustment system. It can increase or decrease the number of working cylinders of the compressor according to the change in the suction pressure of the compressor to make the system The evaporation temperature remains stable. Low-voltage relays can also be used as low-voltage protection devices for other equipment in the device.