Ever wonder how air compressors work?
Not specifically your air compressor, but how all air compressors are supposed to work, in general?
Taking a moment to read this page will help you understand how air compressors are supposed to work, and will help you figure out what is wrong with your air compressor when yours doesn’t.
What the air compressor does
Everyone thinks air compressors compress air. That is true.
But also, the air compressor is an energy converter. The DIY type air compressor you have in your home, garage or small workshop takes in electricity as a power source, and converts that electricity into compressed air energy. Compressed air energy is stored in your compressors air tank, and waits, ready to use, until you plug the air line into an air tool. Then ‘bam’, that stored compressed air energy flows out of the tank, down the air line, and goes to work for you via your air tool. As long as you have sufficient air pressure in the compressor tank, your air tool will continue doing work for you without using any more electrical power.
How air compressors work – specifically
When an air compressor motor starts, it begins to operate the compressor pump and that compressor pump sends air into the air compressor tank. The compressor tank on your air compressor tank might be the size and shape of the one in the photo, or your compressor tank may be a pancake style or a stacked tube style. Regardless, when the pump starts pumping, air should flow from the pump into the air tank on your compressor.
The air compressor motor starts either because the compressor is on and you are using compressed air, and the air pressure in the tank falls below the pressure switch cut in pressure setting of your air compressor, or, you just turned your air compressor on (assuming yours has an ON/OFF switch or you just plugged it in if it doesn’t) and the air pressure in the tank is below the cut in pressure level.
Quick Tip: If you turn the compressor on or plug it in and nothing happens, look at the pressure gauge on the tank. If that pressure reading is above the pressure level where your compressor normally starts, then your compressor will not start. Make sure you are looking at the compressor tank gauge and not the regulator gauge.
This next photo is of a typical pump on a smaller air compressor.
You can usually identify the pump as it is made of metal, and has exposed metal fins. Sometimes these fins are on the side of the pump, some times on the top, and often both.
The purpose of these fins is heat dissipation. Compressed air generates a lot of heat, and the fins are adding surface area to the metal of the pump, and this increased surface area allows faster heat transfer from the metal to the surrounding air.
The small air compressor manufacturers sometimes shroud their air compressor pumps and motors entirely inside a plastic cover. This, I guess, makes them look better, at least from the manufacturer’s perspective. My thoughts are thus. If you cover the pump up, you are reducing the speed with which the heat build up can be transferred to the surrounding air. Too much heat is bad for almost any electro-mechanical device. I think shrouding the pump on any air compressor is the wrong approach.
Better to put lots of warnings about how hot it gets around the pump and leave it open to get rid of compressor pump generated heat faster as far as I’m concerned. Besides, you’ll only have to touch the compressor pump from a running air compressor one time to realize that it gets darned hot (yes, it will burn you) before you realize that touching it isn’t a good idea! 🙂
But, back to how air compressors work.
So far we’ve talked about the compressor tank that stores the compressed air, and we’ve talked briefly about the pump that sends the air into the tank. Your pump may or may not look like the one in the photo but if you have a compressor, then you have a pump of some kind on it.
Pressure switch turns the compressor on and off
When the air pressure in your air compressor tank falls below a certain level, the air compressor should come on to rebuild the pressure in the tank. The device that turns the air compressor on and off is the pressure switch.
Depending on your make of air compressor, the pressure switch on yours might be one like the Condor in this photo. The Condor make has an internal unloader valve.
Your compressor switch might also be a Lefoo type (or other Chinese made comparable switch), with an external unloader valve.
What unloader valves are and what they do on your air compressor will be linked from air compressor equipment on the navigation bar at the top of the page.
Both of the Condor and the Lefoo type of compressor pressure switches are normally located on the discharge pipe from the air compressor tank.
If yours is a mini-compressor, you may not even be able to see your pressure switch, as it could be inside the housing.
Regardless of the type of pressure switch you have, they all work in a similar fashion.
Pressure switch settings
The pressure switch on your air compressor will arrive with factory preset pressure set points.
One of those pressure switch set points will the the cut in pressure setting. This is the lower pressure set point. When the air pressure in the compressor tank drops to this set point, the points inside the pressure switch close, electricity flows through the switch to the motor circuit, the motor turns on and starts driving the pump, and the pump starts sending air down into the compressor tank.
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