Overloads Motor

by Oscar
(Farmingdale NY)

My Cambell Hausfeld 2 HP air compressor is set to go off at 180 psi.


But as the air builds up to 100 psi the motor starts slowing down and the belt starts squeaking.

But the motor some how manages push slowly past 100 psi and then starts running well till the cut off pressure is reached.

All this started recently when I changed the pressure switch. Can you tell we what is wrong.
Thanks.
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Bill says...

Oscar... this is a weird one.

First question; do you hear the psssshhht of the compressor unloading when the pressure in the tank finally reaches cut out pressure level? In other words, does it unload properly? Probably does, but I'm curious.

The belt starts squeaking, I think, because the motor is trying to rotate the motor sheave at a constant pressure, the compressor sheave is binding or something is slowing it down, and that is causing the belt to squeal on the compressor sheave.

Therefore, something is logging down your motor in the affected pressure range. I am at a loss to figure out what might be doing this within the pressure range you describe, and changing the pressure switch shouldn't have anything to do with any of the symptoms you describe.

Gosh, wish I could offer more. Anyone else?

Cheers,

Bill


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used compressor pressure switch taken apart

by Preston
(Dallas, TX)

pressure switch

pressure switch

i recieved a compressor that is pretty old and in dis-repair. it is a craftsman 106.152740 paint sprayer. when i got it the compressor was locked with rust in two of the four cylinders and the pressure switch was taken apart. the original owners had it stop working on them so they took the pressure switch apart and directly wired the morot to the wall. it still did nothing so they threw it away in a dump pile. this is where the water got into two of the cylinders. all they had to do though was reset the motor. i picked it up, reset the motor and the motor works fine, i am in the process of restoring the compressor but cannot figure out where the wires go on the pressure switch. it looks different from all other pressure swithes i have found online. if you could tell me where the wires are supposed to hook up that would be awesome! i do not have the lid or anything else, the picture shows it all.
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Hey Preston. Very nice to hear from you.

The pressure switch does two things. It toggles the compressor motor on and off as necessary, and it opens and closes the unloader valve to dump the air trapped over the pistons.

The switch should have a supply line from the tank, and that's normally the pipe that it's sitting on.

I can't tell from the photo how this particular switch interfaces with the unloader valve, but it must.

I also don't know your voltage or HP motor size.

You can replace the pressure switch once you figure out how it gets the air signal from the tank, and how it toggles the unloader valve.

With this info, you can visit your local compressor store to get a new one, along with wiring information.

Cheers,

Bill



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Moror will not shut off when high pressure is reached

by Scott
(Florida)

I had a problem with the pressure switch not tripping the contacts. The manual on/off switch also located on the pressure switch would not work to turn the compressor off. I replaced the switch with a factory replacement and I still noticed that the invoice for the new switch says 100/135 pressure switch. The tank says that the safe operation pressure is 125 psi and the old switch is marked 125 psi. Is it safe to use the 100/135 switch?






Bill says...

That's an difficult question. I don't know the condition of your compressor or if it will become unsafe operating at 10 PSI over the recommended settings.

You can either adjust the pressure switch settings to bring it more in line with the compressor needs, or take a chance.

Myself, I wouldn't worry about the 10 PSI pressure increase, but I'm not you. You do what you want.

I would also be wanting to set the cut in pressure in the 80 PSI range instead of the 100 it is now.

Cheers,

Bill

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Compressor building too much pressure

by Pat
(cottam)

I have a husky 7hp 60 gallon compressor. It turns on builds pressure up to 135psi then "pops" the safety valve and continues to run. It won't shut off. How can I turn down the amount of psi it builds? The tank is about 6 years old. I am not sure where the adjustment is? There are 2 allen key screws on the back of the switch, one small (aprox 5/16) and the other is aprox 3/8?

thanks






Bill says...

Pat, it didn't always do this, did it?

Although it seems to me that to have your PRV letting go at 135 PSI seems a bit odd, if your compressor isn't rated for higher than that, then that's why the PRV lets go at that pressure.

Unplug the unit, and look under the cover of the pressure switch. Some of them show the pressure settings for your compressor under the lid. If it's there, what are the pressures for high and low pressure switching?

I'm thinking that you may need a new pressure switch.

Cheers,

Bill

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Compressor won;t shut off automatically

by Bud
(South Jersey USA)

Campbell-Hausfeld mode;l C1071080VMSA, magnetic starter, wired for 220.

Turn on power and compressor starts fine, builds to 175PSI, then pressure switch hisses and opens points, but compressor still runs and pops safety valve.

Replaced pressure switch, problem still there.
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Bill says....

Hmmm, this is a weird one, Bud.

If you think of it, the pressure switch is just a switch. When the switch is turned off (the high pressure cut out pressure is reached and the points open) then power stops flowing to the electric motor and the motor stops.

In your case, the pressure switch is opening (at least you think it is) and the motor continues to run.

Therefore, power must still be reaching your motor even when the switch trips, and you must either have a failed switch or you have a path to the motor for power to flow even when the switch is off.

You have an electrical problem I'm sure, and you need to bring in an electrical expert to solve this problem.

Cheers,

Bill

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Air compressor pressure switch problems

Hi- I have a Classic brand air compressor purchased at orschelen a number of years ago.

It has an 80 gallon tank and two stage compressor.

The last while I have been having trouble with it not shutting off. It will run all day with the pop off valve blowing air periodically if not unplugged.

The on off switch on the pressure switch doesn't do a thing. We took the switch apart and cleaned it up, but it didn't make a long term difference. Any ideas?

The brand of compressor is not sold anymore and can't be found online, so I think I may just order a replacement switch unless you have another idea of how to trouble shoot the switch.

My switch looks almost identical to yours in the articles on this site about pressure switches. What do I need to know to order? We usually run around 150 lbs of air in the tank at cutout. Thanks






Bill answers...

Howdy, and thanks for writing in.

Yes, it sounds to me like your pressure switch has failed on the cut out level, and you need to get it fixed...fast!

If your PRV fails too, you'll have a real serious problem.

Take the old pressure switch with you when you go to buy the new one. Make sure the new one will work the unloader valve on your compressor. It will likely have an adjustable high and low point. Set those pressures at the same level the old one had.

Cheers,

Bill

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