Air compressor is down

Heads up,

The contactor on the air compressor has gone out again.

I am talking with ingersoll Rand to get a replacement contactor quick. With any luck, we’ll have it back up and running in a couple days.


Okay, new 'power switch’s is installed and the compressor seems to be working fine now.

The compressor should not get above 130psi. If it hits 150psi, you will start hearing a loud angry ‘PFFSSSTTT’ noise from the compressor, possibly repeatedly… Those are what I call ‘bad noises’…

If you do hear one of the over pressure valves popping off, please put a lock out/tag out on the compressor immediately and shoot a message to

I would rather have to replace a $75 ‘power switch’ than a warped $300 compressor valve plate.

Otherwise, I think the compressed air system is now fully functional and labeled.

Also… Be aware that with the nice new air dryer donated by Ingersoll Rand, the system now randomly makes smaller ‘pfft’ noises independent of the air compressor running.

(Note where the needle is on the gauge, if it hits 150psi, shut off the compressor immediately!)

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Is there a shutoff for the compressor once it reaches a certain PSI?

That’s what that switch is suppose to do when it works right.

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Are the switches welding themselves shut? Or is it a mechanical issue with them? What if the pressure switch drives a contactor so this doesn’t keep happening? I’ve never seen a compressor go through so many pressure switches

Not 100% certain. I have not taken the old switch a part yet, but I think this one might have some gunk stuck in the pressure switch.

The first compressor welded the contacts, and blew the headgasket.

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Thanks, that’s what I’ve been kinda dancing around. I used to be an Automation/Controls Engineer and have never seen an air compressor go through so many issues either. Motor contactors need both overload and over current protection…I’m sure either @whateg01 or I could design a solution to prevent the air compressor from going through so many contactors.

Rustin races to the makerspace to write ‘do not hack’ on the compressor…

Seriously though. It may be worth it to draw something up and see if it makes sense.

Is the pressure line open to the switch?

So, a motor starter? I don’t recall for sure, but being a single phase (assumed to be) compressor duty motor, I would expect it to carry its own thermal protection. I don’t recall the pressure switch having any smarts built into it, so I am pretty sure it’s a simple pressure switch only. AFAIK, to retain the existing safety measures, but add reliability, the only thing that needs to be added is a non-latching contactor with 240V (or in this case, I guess 208V) coil. Something like this.

Someone needs to do their best Jean-Luc Picard impression and say “Make it so” (that sounds like “Make it show”) with an air of dignity --that only an old bald Englishman with Shakespearean training in the theatre and who uses that as he plays a future space-faring Frenchman with an English accent-- can provide.

You guys are welcome to come up with a new control system for the compressor. I think the connection to the tank is a 1/2in fitting.

My requests are the following:

  1. Any work done does not put the air compressor out of commission for more than a day (it’s getting a lot of use already)
  2. Should something go wonky with the new setup, the metalshop lead (current or future) should still be able to swap back to the old power switch in an hour or two.
  3. Document on the forum what you did and why you did it.
  4. Cost of parts does not exceed the cost of replacing the cylinder head.
  5. You guys have fun making it work.