Tag-Teaming Two Compressors

You can boost volume, but not pressure, by hooking two compressors to the same air line. Here's advice. October 28, 2008

I heard a story about connecting two small compressors together in order to increase PSI. Maybe it will be helpful in certain spraying applications off site. In theory, I guess this is like a two stage motor. In actual practice, however, does it work? If so, how do you do this?

Forum Responses
(Finishing Forum)
From contributor R:
I have never heard of doing this. What are you trying to do? For spraying you need more volume, not pressure.

From contributor P:
Really bad idea. You can't feed high pressure air to the input side of a compressor. Hook them up in parallel, if both have same output pressure. Even that is not a great idea. They may not be balanced together, limits may not trigger at the same time, and could conflict with each other.

From contributor T:
I do it all the time. Connect the outputs of each compressor together with a T joint. The PSI will remain about the same but the volume of air available to drive the tools will be doubled. I am able to run an air sander for much longer lengths of time at a go. On just one, it runs out quickly. I would imagine that the output line pressure will stay at the higher machines pressure for longer.

From contributor J:
I agree with most of the above. The advantage is in increased volume, not pressure. Trying to make a 2-stage compressor by connecting 2 single-stage compressors in series, with the outlet of one tank feeding already-compressed air into the intake of the second compressor's pump is nutty; it won't work and will be dangerous.

Connecting 2 compressors to the same tool using a tee of some sort is called in "parallel," not "series."

The only part I soft of disagree with is contributor P's concern about connecting 2 compressors in parallel. It may not be ideal, but I can't see any inherent hazard so long as the pumps are similar and set to similar pressures. It would be bad to tee together a big 2-stage industrial compressor with a little pancake unit, but 2 jobsite compressors together shouldn't be a problem.

From contributor A:
You will accomplish two things by placing a second compressor and tank in the same air system.

1. Max volume of air supply.
2. Recovery time.

You need to eliminate the second pressure switch. Both compressors need to turn on at the same time, otherwise one will be doing most of the work. It should make little or no difference if you hook the compressors in line versus teed into the main line. Theoretically you could place the second compressor anywhere in the system and as long as the pumps start at the same time, it should be of little consequence. The working pressure of most compressors is about 125psi. I'm not sure why you would need higher.

From contributor G:
This is quite common in some applications. You can get special switching gear that starts one compressor, then if the pressure continues to drop another preset amount, the second compressor starts. The second time the other compressor starts first to balance the usage. I think it is called duplex switching.

You can replicate a part of this by just setting one compressor to kick in 2 or 3 pounds under the other. That way if the first one kicks in and the pressure continues to drop the second one kicks in. Set the new one to kick in first as you won't be able to alternate. T them together. There is no way to hook them in series.

From contributor D:
We do it all the time. Simply place a T fitting in one compressor. We use the one we use for our nail guns, then hook a hose up to the 2nd compressor. It is best that one has a large tank. We hook up a pancake to a 20 gal tank and we then enough air to push a 2 1/2 gallon spray pot. The 20 gal would run out of air but the pancake puts out just enough to keep the pot working all the time. The one with the lower psi will always shut off first but it is not that much of a difference to even warrant dealing with. So what if one runs an extra minute or so - it will shut off when both tanks reach the shut off PSI.

The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor A:
Connecting the compressors together is ok if they both are about the same in output. I use a 4.5 gal 5.6 cfm Dewalt to a 8 gal 4.5 cfm harbor freight compressor. I do this for a number of reasons. First it increases the cfm and allows me to run my soda blaster (you should keep them both at same psi). This setup also lets you power each compressor with a different outlet which uses less power from each outlet so you have less of a chance to blow the fuses. The setup is also much quieter and less expensive to buy. The video below may be helpful.