Adjusting The Pressure Switch On An Air Compressor
Compressors come factory set at a certain pressure. When they are turned on, the machine will run until the correct pressure is reached, and will not turn on again until the pressure has dropped at a predetermined setting. Can these settings be adjusted if more or less pressure is needed?
Most pressure switches on compressors can be adjusted as needed. It only takes a little bit of know-how, a few tools, and a bit of testing to make sure the proper settings have been met.
How Much Pressure Is Needed?
Many pneumatic tools need between 70 to 100psi to operate correctly, but there are times when more or less pressure is required for the job. In a setting where lower pressure is needed more often, there could be significant cost savings associated with lowering the pressure and cut on/off settings.
If only a max of 50 psi is needed, there’s no need to have a large compressor keeping 150 psi in the tank all the time. By adjusting to a lower pressure and cut-on and cut-off setting, the energy and monetary savings will be dramatic.
Alternatively, if tools or applications require more pressure than is factory set on the machine, then adjusting the pressure on the compressor will make the job flow more smoothly.
A nail gun for example may need more pressure than is factory set. If the nail gun is consistently leaving the heads sticking out, the pressure needs to be increased. When the nail gun sinks the nails too deep into the wood, then the pressure may need to be backed down a bit.
Adjusting the pressure switch in a compressor can make a job more efficient and easier.
Explaining Cut-In And Cut-Out Pressure
Cut-in and cut-out pressure are the points at which a compressor will start up and start compressing air and the point at which it shuts itself off. For example, an empty compressor will turn on and run until it reaches 100 psi. This is the cut-out pressure setting.
The motor will then stay in standby mode until the pressure drops down to 85 psi, at which time the compressor turns back on, this is the cut-in pressure setting. The machine will build up pressure and stop again at 100 psi. The pressure between when a compressor cuts in and cuts out is called the pressure differential.
The pressure differential can often be adjusted when adjusting the pressure switch. Some brands don’t allow the pressure differential to be tinkered with, and only allow the cut-in and cut-out settings to be altered.
When setting the cut-in and cut-out pressure, there needs to be a moderate pressure differential between the two, or the compressor will constantly be starting and stopping. This will increase the workload on the compressor motor, which can cause it to quickly burn out.
A good rule of thumb for setting the pressure differential is considered to be one bar which equals 14 psi. For larger machines, or compressors that get a lot of use, setting the pressure differential higher is better. For these applications, setting the differential at 2 or 3 bars may be best, but check the owner’s manual as the pressure differential may be noted inside.
Setting a slightly higher pressure differential will help to reduce moisture and condensation in the compressor. As the compressor motor runs, it will heat up, this heat helps to evaporate moisture before it has a chance to enter the tank.
Moisture in compressed air can be bad for the compressor and tools, so any way to help reduce the humidity is beneficial.
How To Adjust The Pressure Switch On A Compressor
Here are step-by-step instructions for adjusting the pressure switch on conventional, piston-driven air compressors. Commercial or industrial rotary screw compressors can usually be adjusted at the display on the front of the machine.
1. Notate Cut-In and Cut-Out Pressure
Turn the compressor on, and write down what pressure the compressor stops at. Then attach an air nozzle to the hose. Use the air nozzle to drain air from the tank until the compressor turns back on.
Write all these numbers down in order to keep track of where the cut-in, cut-out, and pressure differential sit. This will be important in calibrating the compressor because there are unfortunately no marked increments on the pressure adjustment screws.
2. Access the Pressure Switch
Take off the plastic covering to get to the pressure switches, and set it aside. This usually only has one or two screws and possibly a tab. The tab may be difficult to dislodge, so be careful when taking it off to prevent breakage.
Depending on the make and model of the machine, there could be one or more screws to adjust the pressure settings. There are even a few brands that do not have a pressure switch. If there are no springs, screws, or bolts with nuts, it could be a factory set compressor that is unable to be adjusted.
Look for some type of springs held down with screws or bolts. These could be phillips head screws, hex nuts, or they may require allen wrenches to adjust them. Each make and model air compressor will be slightly different.
3. One Screw Switches
For compressors that only have one adjustment screw, all that needs to be done is to turn the screw, or hex nut, clockwise to increase the cut-out and cut-in pressure. In these pressure switches, the pressure differential is always constant and cannot be adjusted.
These factory-set pressure differential switches are typically set at 20 psi. An example would be a compressor that is set for 100 psi max will cut in when the pressure in the tank falls below 80 psi.
Find out the cut-in and cut-out range of the compressor then adjust the screw. Either release pressure with the air nozzle to see when the compressor turns on and shuts back off and see if the pressure is where it needs to be. If not, adjust the screw until it reaches the proper psi.
Tips To Make Things Easier
- It may be beneficial to note where the screws or bolts are set if the factory settings will be needed at a later time. Use a permanent marker, small paint brush, and paint, or nail polish to mark the spot where the screws or bolts are sitting. It can also be beneficial to note or write down which way the screws are turned and how much they are turned each time.
- Consult the owner’s manual, or look under the plastic cover. One or both of these places may show which set screw adjusts what pressure.
- Always adjust one screw at a time, then turn the compressor on and notate where the machine cuts off or cuts on. Turning all the screws right off can make it very difficult to adjust the pressure.
- Never start adjusting the pressure switch with an empty tank. Things can get confusing when pressure switches are adjusted before there is any air stored inside.
- Also, be sure to only turn the screws or bolts in small increments at a time. A quarter turn to half a turn each time will keep from going too far between adjustments.
- Turning the screws clockwise increases pressure or increases the pressure differential, while turning them counter-clockwise will decrease pressure or lower the pressure differential. If there are only one or two screws, then the pressure differential will always stay the same.
- The pressure differential switch will be separate for the cut-in and cut-out pressure switches. It’s often smaller than the others and sometimes will not need to be adjusted.
Compressors With Two Adjustment Screws
Compressors that have two screws in the pressure switch have settings to adjust the cut-in pressure and a smaller screw—usually flat-head—that adjusts the pressure differential. The way these works is the cut-in pressure is set, say at 50 psi, then the differential pressure is set which also sets the cut-out pressure.
At the factory, the pressure differential is normally set at 20 psi. So the compressor that has a cut-in pressure of 70 psi, will cut off at 90 psi. Read on to find out how to adjust the pressure for this type of compressor.
Adjust The Cut-In Pressure
Start by following the first steps above to the point when the cover is removed. Next, adjust the cut-in pressure to the desired setting. For example, say the compressor is set to cut-in at 50 psi, but it needs to be set higher at 70 psi.
Turn the cut-in pressure screw clockwise about a quarter to half a turn. The compressor should turn itself on. Let it fill and shut itself off.
Next, while the compressor is still turned on, slowly release pressure until it starts back up. Note where the compressor starts again. If it starts before 60 psi (or whichever pressure point is needed), adjust the screw again and repeat the process until it cuts-in where it’s needed.
If the compressor is creating too much pressure and needs to be adjusted down, follow the same steps as above, only turn the screw counter-clockwise to decrease the cut-in pressure.
Once the cut-in pressure is properly adjusted, move on to the pressure differential screw to set your cut-out pressure. The cut in pressure will remain where it was set. Keep in mind not to set the pressure differential too wide apart.
If 100 psi is needed, then the differential shouldn’t be set at 50 psi. There should only be between 14 to 25 psi differential.
Compressors With Three Set Screws
These compressors have both a cut-in and cut-out setting as well as a smaller differential set screw. Simply follow the instructions above, continuing to set the cut-in pressure first, then set the cut-out pressure.
When setting the compressor this way, there isn’t a need to adjust the pressure differential because it gets set by adjusting the low and high pressure on the tank. It just makes it less confusing to adjust the cut-in and cut-out pressure only.
ALSO READ: Air Compressor Pressure Switch Wiring Guide
Conclusion
Adjusting the pressure on a compressor isn’t difficult when the proper instructions are followed. There may be a little bit of a learning curve to getting it just right, but with patience, it can be completed relatively easily.
