Air compressors are critical for operations in industries ranging from pharmaceuticals to manufacturing and electronics to healthcare. High-quality compressed air is essential for product integrity and operational efficiency.
You rely on your air compressor, but what do you know about how it works?
The air compressor pressure switch is one key component of the compressor. The pressure switch helps ensure you have the pressure you need. It keeps the air compressor performing properly so your operations can stay on track.
Learn more about what an air compressor pressure switch does and why it’s so important.
Table of Contents
What Is an Air Compressor Pressure Switch?
An air compressor pressure switch is responsible for maintaining the correct air pressure in the air tank. It’s a mechanical pressure-activated electrical switch. Pressure switches are a critical component of all types of air compressors.
The pressure switch allows power to the motor when the system pressure dips below a specified level. It cuts off power to the motor when the pressure gets back up to the desired value.
Parts of an Air Compressor Pressure Switch
The pressure switch usually looks like a small rectangular housing. It’s around the same size as your palm. It’s usually mounted on the reservoir.
An air compressor pressure switch has several components.
Terminals
Incoming and outgoing power leads connect to the pressure switch through the terminals. The switch either completes or breaks the electric circuit.
Contacts
The contacts are made from conductive materials. They end at the terminals. They come together to complete the circuit or separate to break the circuit.
Diaphragm
The diaphragm is a piece of flexible material. It moves when the pressure in the tank changes.
Pressure Switch Relief Valve
The pressure switch relief valve is a safety valve. It relieves pressure trapped between the pump and the check valve. It’s located on the base of the pressure switch and is plumbed into the top of the check valve with a copper or nylon tube.
Adjustment Springs
The adjustment springs allow you to adjust the cut-in and cut-out points for the air compressor. Some pressure switches have a secondary spring that lets you adjust the difference between the cut-in and cut-out pressure.
Tightening the spring means the diaphragm needs to apply more pressure before the spring forces the contacts apart. Loosening the spring lets the diaphragm move with less pressure.
Auto/On/Off Lever
Some air compressors have a lever or knob to control the pressure switch. In the “auto” or “on” positions, the motor will turn on and off with the established cut-in and cut-out levels. In the “off” position, the power to the engine is off.
The lever should always be set to “off” before plugging in or unplugging the air compressor.
How Does an Air Compressor Switch Work?
All air compressor switches work basically the same way. The air pressure in the tank gradually increases and builds up cut-out pressure. This backward pressure changes the shape of the diaphragm.
When the diaphragm deforms enough, it pushes against a mechanism that breaks contact inside the switch. This prevents power from getting to the motor circuit in the compressor. The compressor stops pressurizing the air in the tank.
The pressure relief valve opens to release back-pressure between the pump and the check valve.
While the air pressure stays constant, the diaphragm remains deformed. When the pressure drops far enough, it reaches the cut-in setting. The diaphragm will go back to its original shape.
The circuit closes again, and the motor starts running. This cycle continues as long as you’re using the air compressor.
Setting the Cut-In and Cut-Out Pressure Values
You can set the cut-in and cut-out pressure on your compressor switch. You’ll do this using the adjustment spring. Before working on your air compressor, be sure to unplug it and drain all pressure from the system.
Turning the adjuster knob or screw changes the cut-in and cut-out settings. Turn the main spring clockwise to increase the setting. This compresses the adjustment spring, meaning the diaphragm needs more force to move the contacts.
Turn the main spring counterclockwise to lower the setting. This decompresses the spring, which makes it activate using less force.
The range between the cut-in and cut-out settings is the differential. Some switches have a fixed differential, which is usually between 0.8 to 1 bar. Other switches let you adjust the differential.
If your air compressor pressure switch has an adjustable differential, it will have a separate spring for that purpose. You can turn it clockwise to increase the differential or counterclockwise to lower it.
Air Compressor Pressure Switch Testing and Replacement
Testing your air compressor switches periodically helps ensure they are still working efficiently. You can avoid pressure-related problems with the compressor and help prevent damage. You avoid disruptions to your operations.
Disconnect the air compressor power supply before testing the pressure switch. Then, you can disconnect the wires that link the pressure switch and the terminal block. Leave the wires that power the switch connected.
Use a multimeter to check continuity across the contacts in the switch. This verifies whether the switch can conduct electrical current.
Next, apply air to the pressure switch using the valve. Put the leads of an ohmmeter or multimeter on each of the disconnected wires. If the ohmmeter reading is 0, the switch is closed and working correctly.
If the reading shows the circuit is open, try turning the adjustment spring. If you can’t get the ohmmeter to read 0, the pressure switch needs to be replaced.
Some problems with air compressor switches can be repaired. Repairs are difficult, though. Replacement is often a better option.
Buying an Air Compressor or Air Compressor Parts
An air compressor pressure switch is essential for the performance of your air compressor. It helps ensure that you have the right amount of pressure for your equipment.
You can rely on Swift Equipment Solutions when you need air compressor parts. If you need a new or used air compressor, we also have a wide selection.
The team at Swift Equipment will use their extensive experience to help you get the right air compressor for your operation. We want to earn your business for the life of your enterprise, not just for a quick sale.
Contact Swift Equipment today to find a quality pressure switch or air compressor that meets your needs and fits your budget.
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