HELP! Dumb move with my new Quincy Q13160VQ

[Brandon Thill]

In my rush to wire the terminals I started unscrewing what I thought was the ground. Quickly realized it wasn't and was tied to the unloader. So now I need to readjust it. I operate some big industrial compressors at work so the operation isn't totally foreign to me, but I'm not sure exactly how they implemented this pressure/unloader switch and how best to adjust it safely. I did not touch the pressure adjustment. As I understand it, at max pressure the pressure switch shuts off the power (screw marked P) and the unloader is opened to vent compressor pressure (screw marked J)? I'm assuming there must be check valve int he fitting I marked in the pic so it just vents the comp. What should I be looking for at each stage of operation to know the unloader is at the right adjustment? How does the screw direction change the unloader operation?

[Bill Dufour]

That may be the differential adjustment.
I do no understand the plumbing. The switch diaphragm has to see tank pressure at all time. Any check valve is between the pump and the tank. I do not see how the pump air gets into the tank. Often the switch is supplied from a totally different bung in the tank.
Bil lD

[Brandon Thill]

Here's a better view so you can see the unloader tube a bit better. I only assume the J screw i messed with is connected to the unloader tube only because it is directly above where the tube attaches. But that might not mean anything.

[Brandon Thill]

So thinking about this a bit more, that J screw is not an adjustment for the unloader, the tube just happens to connect below it simply because both the unloader valve and that J screw adjustment are tied to the pressure switch? So does the P screw control a "center" pressure and the J screw the width of the band around that pressure to start and stop and the motor?

[Brandon Thill]

Ok so...think I'm wrapping my mind around this now. I have no experience with these small shop compressors, so let me know if I'm off track. Quincy lists this as 110 to 135psi working pressure (135psi max). So I assume it turns on <110psi and turns off >135psi. The J screw adjusts the size of that differential: 135-110= 25psi? So as long as it starts/stops at the listed pressure it is adjusted correctly and I didn't mess anything up too badly? Or more technically as long as the J screw is set to 25psi differential and the P screw is centered at 122.5psi it should operate to spec?

[Brandon Thill]

Everything is working properly!

[Brandon Thill]

Does anyone think it is a problem to run the compressor at 0 psi with the outlet open all the way? I want to put some hours on it and change the oil soon. With no pressure the temps are much lower on the compressor itself, would this cause extra wear if the parts are too tight due to the lower thermal expansion?

[Matt Mattingley]

Brandon, the screw that you adjusted has nothing to do with the head pressure bleed off valve. I believe it holds the top plate of the contacts securely in place. One thing to make sure as to always turn the power off to bleed the head pressure and stop the contacts from engaging if nobody is in the building. Just above the big tank check valve there is a clear plastic line that feeds the pressure control contactor. This is the head pressure relief pipe. It is attached to a needle valve that is triggered to relieve head pressure after shut down. At the point where the check valve enters the tank that plastic bleed line tends to get hot and sometimes pops out. In the right situation but pump just keeps trying to charge the tank and the motor keeps running. Something usually goes wrong. I usually like to swap it out for a quarter inch copper.

[Wayne Lomman]

Compressors like this are designed to run intermittently. Running it for some hours constantly is working outside its design parameters. Just get to work with it and change the oil early. Cheers

[Mike Cutler]

Does anyone think it is a problem to run the compressor at 0 psi with the outlet open all the way? I want to put some hours on it and change the oil soon. With no pressure the temps are much lower on the compressor itself, would this cause extra wear if the parts are too tight due to the lower thermal expansion?

I wouldn't do it.
Let the compressor break in by itself. If it needs 6 months or a year to finally get the required hours for the break in, let it do it on it's own.
Compressor motors are not 100% duty cycle motors. They're designed for on/off duty cycles. Leaving the outlet open is going to create a big D/P across the compressor unnecessarily.

[Joe Jensen]

There may be a duty cycle rating somewhere. The Quincy dealer I bought parts at said they test new import compressors before adding them to their line by opening the drain and running all weekend. By Monday morning nearly every one burned up. I'd be very careful doing this...joe