Valve to dump air between pump and tank on Quincy compressor

by Mike McCullough
(Lawndale, CA)

Good site Bill.

I have a 25 hp Quincy reciprocating unit that I have the pressure switch set a 140psi for shut off and 100psi for start up.

I originally had it plumbed straight to the tank with 1 1/4 inch line.

The problem is when the unit tries to start up against the 100psi setting, there is the line pressure that the compressor is trying to start up against and it kicks out my overload on the electrical panel.

Quincy told me to install a check valve which I did and it has an 1/8 npt port for a line to go to the Asco 2-way valve to unload the pressure trapped in the line so the unit can start up load free.

Problem is I don't know how to plumb all of this correctly. I need to get this right before everybody comes back to work Janurary 5th. Can you please give me some idea of how this should work and how to install the unloader??
Thank you very much,

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Dec 24, 2014
by: Doug in

Pics of what you have might help, but, absent that;
you run the check valve port to the Asco port, assuming it has one.

The Asco port will be blocked anytime the compressor is running: when the pump is on, all air should go into the tank via the check.
When the pump stops, the check will close, keeping air in the tank; at the same time, the valve on the Asco should open, letting pressure on the main line from the compressor to the check to leak off.

The main tricky things might be that the Asco doesn't have an unloader port, and the check must be installed correctly.

If that doesn't clear it up, you can post anew with pics and/or part numbers, mainly of your pressure switch (the asco, right?)

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