Pressure Switches for Compressed Air Control

Pressure switches are your compressed air system’s safety net. They control the pressure of the air present in your system and, in turn, make the system more reliable. This equipment is built to react to changes in pressure.

These mechanical devices rely on air pressure to control and operate an electric air compressor. If the pressure is below the specified threshold, the mechanism completes the circuit and powers the motor. Most pressure switches include a pressure relief valve, which makes starts easier. 

Pressure Switch Components

Typically, pressure switches will have six main components:

• Terminals
  • By either completing or breaking the circuit, the pressure switch tells the air compressor when to turn on. The terminal is the connection point between the incoming and outgoing wires.
• Contacts
  • Contacts are the point that sends the signal about operating. These components are made of a conductive material, so that when the contacts are separated, the signal stops. 
• Diaphragm
  • Also referred to as a membrane, this piece of flexible material moves when the air pressure changes. As the air pressure increases, it pushes against the membrane. This continues until the desired pressure is reached, and the contact points lift off, breaking the circuit of your compressed air system. 
• Pressure Switch Relief Valve
  • These safety valves are designed to relieve pressure that has been trapped between the pump and check valve. Located at the base of the pressure switch, it’s connected to the check valve with tubing. And this valve is activated when the contacts disconnect. 
• Adjustment Springs
  • Adjustment springs are how you set the cut-on and cut-off points for your air compressor. By adjusting the spring, you can set the pressure level. When the spring is tightened, more pressure is needed to break the diaphragm connection. Conversely, loosening the spring will result in less pressure being needed.
• Auto on/off Lever
  •  Some pressure valves have an auto/off or on/off knob or lever to control the pressure switch. When it is on the “auto” or “on” setting, it will work with the determined settings to determine when the motor turns on and off. When it is off, a piece of plastic becomes wedged between the contacts, keeping the power to the engine off.

Without these components working together, you don’t have a pressure switch. The individual components are necessary for the desired result. Without the combination of parts working together, there would be no pressure switch functionality.

How Do They Work

For the pressure switch to function correctly, all components must work together. When the contacts are in place, the motor starts and pressurizes the air. The pressure will continue to build up, and as it builds, the diaphragm flexes. Once the pressure reaches the cut-off point, set by your adjustment springs, the contacts will break the connection to pause the airflow.

Once the pressure drops enough, the contacts restart the signal and send more compressed air. Lower air pressure results in less fluctuation from the membrane. As the pressure lowers, the contacts come back into contact and resume the signal to send compressed air. This cut-in point is predetermined by your springs so you never have to worry about the system cutting back on. During the period where the contactors are separated, the relief valve opens and clears any built up pressure.

This cycle continues as long as the compressor is running. Pressure switches work in the background, but they improve the quality of your compressed air system. Simply having one in place can improve your system.