Help with old compressor?

[Vaughn Kaloust]

OK, not exactly in the woodworking arena, but I am hoping that some of you here might be able to advise me.

I have an old compressor that I have cleaned up, and want to put back in service. The compressor was being used actively up until about 1 year ago, and seems to run fine. I have cleaned it up, drained it and refilled with oil. I know about the tank dangers, but this will be installed in a crawl space beneath my house, along with other equipment like a dust collector and solar hot water tank. Anyway, if it explodes it won’t hurt anything.

This compressor has no automatic cut off switch, so it just runs/stops by switch. This won’t do for my purposes. I have a cut off switch for it, but I want to make sure I plumb it into the right spot. (see picture)

Where I have indicated I think I should install the switch, is on the outlet of the compressor, after a trap of some sort, and before the air enters the tank. Is this correct?

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I also want to know if it is likely that this cut off switch normally has the check valve and un-loader valve included as part of the unit, or are they usually separate components.

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Thanks all.

[Curt Harms]

I'm no expert on this but did something similar with a Campell-Hausfeld compressor with a really crappy pressure switch/unloader assembly. My pressure switch looks pretty similar to yours and is only a pressure switch. I bought an unloader from Grainger and it fits inline between the compressor and tank and upstream of the check valve. I'd think a combination pressure switch/unloader would have more than one air connection.

[Charles Lent]

No, that is not the right place. You should connect the pressure cut-off switch on the tank side of the check valve. From what I can see the check valve is below where your arrow points to, so the pressure cut-off switch needs to connect to the horizontal pipe running between the motor and compressor from this check valve to the tank. The unloader should be connected between the compressor and the check valve (where your arrow is pointing) so that it bleeds off the pressure from the output of the compressor to allow easier compressor starting.

Charley

[John McClanahan]

+1 what Charles said. Also, you could tee off of the pressure gauge for the switch, but the unloader needs to be tied in in the area of your arrow. The pressure switch in the photo has an unloader. Just unscrew it from everything else.

John