This is typically the larger of the 2 gauges on an air compressor.
This is usually the smaller of the 2 gauges. The pressure regulator knob is often right below or beside this gauge where it connects to the airline, though sometimes it is in between the 2 gauges.
The reserve pressure is regulated automatically by a pre-programmed pressure switch. This keeps it within the manufacturer’s accepted range of air pressure PSI. Your air compressor can’t supply any more air pressure than it has in the tank and it won’t go above the maximum pressure set by the manufacturer’s pressure switch.
The outlet pressure can never be higher than the tank’s reserve pressure. This is the only pressure that you will need to manually set on your air compressor each time you use a different tool.
Note that if your tool requires more PSI of air pressure to operate than your compressor has in its reserve tank, you can’t use that tool with your air compressor. You would have to get ahold of a bigger air compressor or find a tool that you can operate using less pressure. Not having enough pressure to operate a tool isn’t usually an issue because pretty much all common air tools operate within a pressure range of 70-150 PSI, which most air compressors can supply. Make sure you don’t set the PSI above the amount needed for the tool you’re using.
Orbital sanders work within a similar PSI range of 70-100 PSI.
Other examples of air tools that work with 90-100 PSI are impact drivers, impact wrenches, ratchets, and speed saws.
A framing nailer is another type of tool that works at a higher PSI of about 100-130.
The reserve tank will automatically stop filling when it reaches the manufacturer’s pre-set air pressure capacity. Always adjust the output pressure for your air compressor when you connect a new tool.
For example, if the output pressure gauge needle is currently pointing to 90 PSI and you are using a nail gun that needs 80 PSI to operate, turn the knob to the left until the needle points at 80 PSI on the gauge.
For instance, if you’re using an air hammer that needs 100 PSI to operate, and the output pressure gauge’s needle is currently at 80 PSI, turn the regulator knob to the right until the needle points to 100 PSI on the gauge.
For example, if you’re using a nail gun and the nails are going too far into the wood, you can try decreasing the pressure by 10 PSI or so in order to make the nails sit flush with the surface of the wood. If the nails aren’t going in far enough, try increasing the pressure by about 10 PSI.
Do not change the cut-in and cut-out pressures on an existing manufacturer-installed pressure switch. There is no need to do this. The factory settings are there to prevent accidents. The cut-in and cut-out pressures ensure that your air compressor’s tank doesn’t become too pressurized and potentially explode. Double-check the manufacturer’s instructions for the new pressure switch to see what the factory-set cut-in and cut-out pressures are. You don’t need to make adjustments if it is set to the same range as your compressor uses.
Some pressure switches only have 1 adjustable screw, which changes the pressure differential, or the range between the cut-in and cut-out pressures. Never make adjustments to these screws if you aren’t sure which is which.
Always refer to your compressor’s owner’s manual for the manufacturer’s recommended cut-in pressure. In general, the cut-in pressure should be around the lowest PSI that you operate tools at. If your pressure switch only has 1 pressure differential screw, turning it will automatically lower or raise both the cut-in and cut-out pressures.
Always set the cut-out pressure to the manufacturer’s recommended PSI, so your compressor won’t stay on if there is too much pressure in the tank. In general, the cut-out pressure should be about 20-40 PSI higher than the cut-in pressure. If your compressor only has 1 adjustment screw, you don’t have to set the cut-out pressure. It changes automatically when you move the single pressure differential screw.
