What Is a Compressor Pressure Switch?

Paul Scott

A compressor pressure switch is a pressure-sensitive electrical switching device used to regulate the operation of an air compressor. The main function of the switch is to start the compressor when the pressure in its holding tank drops below a set low point and to stop it when the pressure reaches a pre-set maximum. This allows the compressor to maintain a constant working charge in the system, an essential criteria for industries that are heavily reliant on compressed air. The compressor pressure switch is typically mounted on the compressor assembly or in another easily accessible location, with the compressor control circuit wired through its internal contacts. A manifold is built into the switch allowing one or more pressure reference air hoses to be connected to it.

Industrial pneumatic compressors power the tools used in each workstation along an assembly line.
Industrial pneumatic compressors power the tools used in each workstation along an assembly line.

Many industries feature compressed air systems of varying sizes, some of which rely heavily on a reliable, constant supply of air. This is particularly true of installations that use large numbers of pneumatic tools or are involved in spray painting and sand blasting operations. Most such industries have large compressors that run constantly to maintain a suitable charge in a holding tank. Built-in pipe systems then feed the compressed air to individual work stations or machines.

One of the inherent issues with this sort of installation is controlling the compressor so as to maintain the working charge. This is where the compressor pressure switch comes in. Consisting of a pressure sensor, a set of electrical contacts, and, depending on the device specifics, peripheral devices such as download levers, the switch simply starts and stops the compressor when required. This is achieved by setting acceptable minimum and maximum pressure levels on the switch using a built -controller. The switch will then start the compressor when the air in the holding tank is depleted to the point where the minimum pressure is reached and stop it again when the maximum pressure is reached.

The compressor pressure switch generally consists of an adjustable diaphragm-type sensor connected to a set of electrical contacts. The compressor motor's control circuit is then routed through the contacts. A manifold that feeds the diaphragm chamber is connected to a reference pressure hose that is connected to the holding tank. A pressure adjustment control allows for setting the two reference pressures according to system requirements. The compressor pressure switch may be mounted on the compressor itself or in a location that is easily accessed by relevant staff members.

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