Quincy Compressor Question

[wbrian63]

Got my new Quincy QV41C60VC wired up last weekend. Attached it to the piping system and fired it up.

I let it run, until I had about 50psi showing on the gauge. Turned the compressor off using the remote switch. To explain, I've got the power for the compressor running thru a 40a definite purpose contactor. That contactor has a 120v coil and is triggered by a switch at the front of the shop. So, I'm cutting all power to the compressor when the contactor breaks.

Checked for leaks in the piping - discovered I'd left a cap off a fitting where a hose reel will be installed after the painting is complete. By the time I'd capped the leak, the tank had fully drained.

Started the compressor again and let it run until the pressure switch shut it off at about 175psi. I then heard what I believe to be the unloader valves venting pressure off the compressor.

I didn't notice this noise when I turned the compressor off the first time at 50psi.

Here's my question, and my concern.

I know that the unloader is necessary to allow for easy startup when the tank's not empty. Under normal circumstances, I'd turn the compressor on when I come into the shop and turn it off when I leave.

Is the unloader triggered when the compressor is turned off when it meets the pressure switch limit, or is it a function of how much pressure is in the tank vs head pressure?

I want to be sure that if I cut the power at any point, fully pressurized or not, running or not, that if I turn the power back on immediately, there's no risk of overloading the motor.

I know that if I cycle the power when the tank is fully pressurized, nothing happens, as the pressure switch keeps the compressor from starting. But what if I turn off the power when the compressor gets to 150psi, and then turn it back on immediately?

Same scenario would be played out if there was a power flash while the compressor was building to cutoff pressure, right?

I've read the manual, and I don't see any answer to this type of question.

Thanks for any input.

 

[scooterseats]

You need to determine if your unloader is a solenoid valve operated by the pressure switch (mine is this type) or if it is centrifugally operated unloader valve that functions by crankshaft speed. This type will unload anytime the unit stops the pressure switch type will not operate until the pressure switch signals it to. Then there can be two types of electric unloader valves. One is power on to unload and would not operate if you turned the power off to the unit regardless of pressure switch signal and the other type would be power off to unload and this would unload anytime you disconnect the power to the unit. Looks like you need to do some investigation.

 

[930dreamer]

Not sure, I thought the unloader operated whenever the compressor stopped. Have you tried stopping before it gets to shut off pressure?

 

[Aceman]

If you bought a new Quincy, is there some reason you can't call the dealer that sold it to you? Or just call Quincy direct?

 

[hofferwood]

Hey wbrian63,
A quick search of your comp.(photos), it looks like it has a pretty typical pressure switch/unloader valve. That means when the set pressure is reached the switch trips and in turn an arm actually presses (or opens) a small valve.
that in turn unloads the head.
You should see a small tube running from the pressure switch to the check valve. If the tank doesn't reach pressure, it wont unload.
The easy answer is T off the tube, use a 120v solenoid valve (N.O. normally open with no power). Wire it parallel with your contactor coil.
If power blips, it will unload, or if you leave before up to press.

Chuck

 

[wbrian63]

Chuck - I believe your description is correct. Look at this picture:

You can see the tube coming from the pressure switch. I did notice that inside the contactor there is a lever that presses on a small pin that sticks out from the tube. If you manually switch off the compressor, the pin is depressed, which I believe will unload the compressor.

I'll look into adding a valve like you describe.

Thanks for the head's up.

Regards

 

[wbrian63]

Update - got a 120v coil 1/8" solenoid valve. Removed the pressure limit valve from the side of the check valve on the top of the compressor. (The installed unloader is attached 180deg opposite from the pressure limit valve).

Added a 1/8" street ell, and a 4" ****** to bring everything up above the motor frame - no room to add anything underneath the frame. Put a T on the ******. One side has the pressure limit valve facing forward. The other has the solenoid valve with the outlet facing the back of the compressor.

Wired it up to the signal circuit for the DP contactor in the control box. When the signal is live, the valve closes.

Tested it - started the compressor and let it pump up to 50psi in the tank. Turned off the power. Satisfying noise of the compressor head pressure unloading thru the valve.

Restarted the compressor with no issues.

Thanks for the input and assistance, guys.

 

[oleguy]

and now you might have void your warenty???

 

[Aceman]

Where'd you get the neutral for the 120v solenoid?