air compressor question

[PromiseKeeper]

I am getting ready to do some body work and painting. I have a 5 hp 30 gal compressor that I know will be marginal. I have access to another compressor that is slightly smaller. Can I somehow hook them up to run in tandem? This would be a one time project. I know it wouldn't make sense to do it long term. The other compressor is maybe a 3 hp and a 20 gal tank.

Could I plumb the tanks together and simply not run the smaller one? I know volume (as posted in another thread that I dint want to hijack) would be a big help. Any advice appreciated! Thanks.
Scott

[Lt.Del]

your output pressure will only be what the last compressor, prior to your gun, will be. I know that is not the factor for considering a tandem, it would be maintain a certain pressure in the tank. I can't see that hooking up a tandem compressor will maintain tank pressure longer in the final compressor...I don't know how you'd hook'em together anyway.
You might be ok w/ a 30 gal compressor.

[bake74]

     Hooking up the 20 gallon tank only and not the compressor part will give you the extra volume you are looking for, and keep your 30 gallon compressor from coming on so often.

[Grim 82]

As already posted, you may be alright with the 30 gallon, and adding the capacity of the 20 gallon to it wouldn't hurt, but do some experimenting before you are ready to put down the paint, and maybe try running a hose from each compressor into a tee, and run the third port from the tee with a hose to the tool/spray gun, and run them both simultaneously so that they can keep up. For spraying you don't need a lot of pressure, but you'll need all the volume you can get.

[jaredts]

If you can plug them both up into separate circuits, it will help tremendously.  I have a 26 gallon compressor and a 20 gallon minus a motor.  I have them tied together in tandem.  When I need a lot of air I let the compressor fill up the tanks and then let it cool down for a while, since it runs for a lot longer to fill up both tanks.  Once you drain some pressure off while you're using it, it takes a long time to fill up again.  Both compressors could fill the tanks quickly once it does drain down and keep your single compressor from getting too hot.  If you have a good 30 gallon compressor that can handle the duty cycle of running 60% of the time for a couple of hours then it might not matter, but you might have to experiment and see.  Either way both tanks will help some.  For mine I ran my 26 gallon directly into the 20 gallon's manifold and from the other side of the manifold into my regulator.  This has solved a long time problem of my junk compressor getting so hot that it burns up seals in my regulator and ruins air hoses.  The smaller tank seems to be absorbing the heat quite well.

[PromiseKeeper]

and maybe try running a hose from each compressor into a tee, and run the third port from the tee with a hose to the tool/spray gun, and run them both simultaneously so that they can keep up.

This is what I had in mind, just wanted to make sure I wasn't missing something that could cause an accident! I would think that the safety valves on both would still function that way and nothing would end up being over pressurized. Am I on the right track here? Jaredts, you had a great point that each one should be on a separate circuit. If possible I would run both units. Thanks guys! Keep the comments coming!