Air compressor won't shut off

[DanielVetpath]

I have an Ingersoll-Rand T30 air compressor in my shop. I bought it used a few years ago and have had no problems. Recently, it gets up to around 175 psi and rather than shutting off, the motor keeps running and it starts venting air from the fitting just behind the pressure switch. This is beyond my realm of experience. Is there an adjustment to change in that switch or buy a new one? Thanks for any help. I will attach pictures of the switch. Daniel

 

[Elginz]

I would guess the points are stuck, probably need a new switch. shut the power off and take the gray cover off with the cap nut. You will most likely see the points mildly welded together.

 

[Zrexxer]

Time for a new pressure switch. They **** out now and then, and are not expensive to replace.

 

[Davefr]

Sounds like the pressure switch isn't breaking contact and/or shutting off the mag starter relay.

Don't use it until you get it fixed.

 

[DanielVetpath]

Any suggestions where to buy a replacement?

 

[pepi]

Ingersoll-Rand.com

 

[Zrexxer]

Any suggestions where to buy a replacement?

eBay, Amazon, Grainger, Zoro, Enco, McMaster Carr, Compressorparts.com, Northern Tool, ecompressedair.com, use your imagination. Or your Google.

 

[DanielVetpath]

Thanks, had to call square d for current replacement. Was able to order locally.

 

[garthg]

Another source:

http://www.cpocampbellhausfeld.com/

 

[garthg]

That "fitting just behind the pressure switch" is the over-pressure valve.
That's a safety device. You don't want to ignore it. It might be smart to put in a new one of those as well. They're only a few bucks.

 

[DanielVetpath]

Thanks, Garthg! I might just replace that over-pressure valve. Thanks for looking out for me

 

[redmondjp]

Thanks, Garthg! I might just replace that over-pressure valve. Thanks for looking out for me

No reason to replace it at all - it just demonstrated that it is working perfectly.

They very rarely go bad and there is no harm done to them when they do vent - they have that ring on them so you can periodically pull on the pintle to ensure that it isn't stuck closed.

 

[Shadowdog500]

Thank god your pressure relief valve was working, or you could have had a tank explosion. My IR compressor has 2 pressure relief valves and I like it that way.

Chris

 

[DanielVetpath]

I should clarify. It was an unloader valve venting - this compressor used to be in an industrial setting and would run continuously. It would just unload when full. It is an intermittent venting - not continuous. The high pressure relief valve right next to it (with the ring in the end) was not venting.

 

[Charles (in GA)]

I should clarify. It was an unloader valve venting - this compressor used to be in an industrial setting and would run continuously. It would just unload when full. It is an intermittent venting - not continuous. The high pressure relief valve right next to it (with the ring in the end) was not venting.

The fact the unloader was venting when it reached 175 is telling us the pressure switch is trying to shut off the motor starter. Operate the unit with the cover removed from the pressure switch and watch the contacts as the unloader starts venting. If the contacts don't open, its welded contacts. If the contacts open, then you have motor starter problems.

Charles

 

[DanielVetpath]

Thanks, Charles. I put lights in my shop based in large on your input a few years ago that has worked out handsomely. I will look into the issues you have mentioned on my compressor.

 

[garthg]

"They very rarely go bad".
This is really very silly, cheapskate advice, especially since these things cost like $3.
When these overpressure valves go bad, and there's another malfunction (as you seem to be having) that's when the compressor explodes. Yes, they rarely explode, but for $3, why not make the compressor as safe as possible?
Tank pressure is usually controlled by switching off the motor, not by venting excess pressure. Or am I not understanding your last posts?

 

[garthg]

I bought a new pressure switch for my Campbell Hausfeld compressor from the CPO link I posted earlier. The kit included a new overpressure relief.

 

[scw1991]

These Pumptrol pressure switches also have a hex nut you can adjust to manipulate the cut-in / cut-out pressure. The switch is preset from the factory to cut-in at roughly 135 psi and cut out at 175 psi (40 psi differential).

Turning the nut to the left will reduce cut-out pressure. Turning the nut to the right increases the cut-out pressure.

 

[Zrexxer]

These Pumptrol pressure switches also has a hex nut you can adjust to manipulate the cut-in / cut-out pressure. The switch is preset from the factory to cut-in at roughly 135 psi and cut out at 175 psi (40 psi differential).

That's about like saying that all cars have blue paint and 15" wheels.

Square D makes dozens and dozens of different models of the Pumptrol switch line, all of which have different specifications.

 

[scw1991]

That's about like saying that all cars have blue paint and 15" wheels.

Square D makes dozens and dozens of different models of the Pumptrol switch line, all of which have different specifications.

My point is there could be nothing wrong with the pressure switch whatsoever. Someone could have easily adjusted the Pumptrol cut-out pressure that exceeded the safety blow off valve pressure rating.

 

[Zrexxer]

My point is there could be nothing wrong with the pressure switch whatsoever. Someone could have easily adjusted the Pumptrol cut-out pressure that exceeded the safety blow off valve pressure rating.

And my point is that it may not even BE adjustable, as many of the product line aren't.

 

[Charles (in GA)]

Tank pressure is usually controlled by switching off the motor, not by venting excess pressure. Or am I not understanding your last posts?

The pressure that is venting is caused by the pressure switch tripping OFF. When your compressor goes off, the pressure switch opens a small valve that is connected to the head of the compressor by a small tube, or to the head side of the tank check valve. Same result either way, the pump stops, and the pressure switch unloader dumps the pressure sitting on the head, ready for the next start.

In the OP's case, the switch is apparently switching off when the pressure reaches 175, as evidenced by the dumping of the head pressure, but either the contacts are not opening, or the contactor in the motor's magnetic starter is not opening for some reason.

 

[Olafur]

Nut sure, but judging by the size of this unit it's a 3 phase. Probably started in star configuration and after few seconds kicked into triangle. Usually 3 relays (solenoids) doing the job. One could be stuck.. But further guessing is pointless without more information.

You could try to shoot some pictures inside the starter box, My bet is your problem lies there.

 

[Pstychologist]

Sure sounds like welded points to me. Cheap enough to replace, but you may be able to file them after separating them and have it run until you can buy new.

 

[redmondjp]

The pressure that is venting is caused by the pressure switch tripping OFF. When your compressor goes off, the pressure switch opens a small valve that is connected to the head of the compressor by a small tube, or to the head side of the tank check valve. Same result either way, the pump stops, and the pressure switch unloader dumps the pressure sitting on the head, ready for the next start.

In the OP's case, the switch is apparently switching off when the pressure reaches 175, as evidenced by the dumping of the head pressure, but either the contacts are not opening, or the contactor in the motor's magnetic starter is not opening for some reason.

But do we know this for sure? In the original post, it sounded like this compressor may have been set up for continuous-run. In this case, the pressure switch could have been used only to unload the compressor while the motor continues to run. Just a thought.

And regarding changing the safety valve, I don't go around changing parts just for the heck of it, regardless of their function or cost. If you pull on the pintle and air comes out, you're good. Explain how that valve is going to fail. If the spring corrodes and weakens, it will blow open at a lower pressure, not higher. There is nothing cheapskate about this advice. And I'd rather have the original American-made valve on their rather than some imported valve of unknown quality anyways.

 

[DanielVetpath]

I only had a second to check today, but checked the contacts on the switch before I turned it on - none of them seemed arced/welded shut - they easily opened manually. I ran the pump up to pressure and noted that the contacts did not open when the unloader valve started to bleed pressure. When I get a change tomorrow, I will open the panel on the starter panel and make sure there is nothing obvious there.

 

[Charles (in GA)]

But do we know this for sure? In the original post, it sounded like this compressor may have been set up for continuous-run. In this case, the pressure switch could have been used only to unload the compressor while the motor continues to run. Just a thought.

I don't get any hint of that from the OP.

I have an Ingersoll-Rand T30 air compressor in my shop. I bought it used a few years ago and have had no problems. Recently, it gets up to around 175 psi and rather than shutting off, the motor keeps running and it starts venting air from the fitting just behind the pressure switch. This is beyond my realm of experience. Is there an adjustment to change in that switch or buy a new one? Thanks for any help. I will attach pictures of the switch. Daniel

He expects it to shut off at 175 psi just like it has been doing for the past several years. Suddenly its not doing that.

 

[DanielVetpath]

Looks like I figured it out. When I realized the contacts were in good shape, I adjusted the high cut off down just a hair and that seems to have solved the problem. I think the guy I bought it from had it set to shut off just before it started to unload. It must have shifted just a bit. Thanks for everybody's input. Daniel

 

[redmondjp]

Looks like I figured it out. When I realized the contacts were in good shape, I adjusted the high cut off down just a hair and that seems to have solved the problem. I think the guy I bought it from had it set to shut off just before it started to unload. It must have shifted just a bit. Thanks for everybody's input. Daniel

Glad to hear it, and thanks for the followup!

 

[scw1991]

And my point is that it may not even BE adjustable, as many of the product line aren't.

Well how about that.....owner adjusted the high cut out and it fixed the problem.