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Country Discussion Topics
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Air Compresser Electrical Q?
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Dieselrider    Posted 03-08-2004 at 17:30:47       [Reply]  [No Email]
Any of you guys or Gals that might know anyting about air compressers or electric motors? We were given a very new 5HP air compresser for the shop, so I can't complain about the price. It's supposed to run on 110 volts but it keeps tripping the 20 amp breaker the second it fires up. If you quick flip the switch and get it rolling the thing will run just fine but, left to itself it trips the breaker on start up. There are two fairly large capacitors on the motor to help start it, could they be too much for a 110 circuit? Could it need a slow blow breaker, and do they make such a thing? Do I need to go to heavier wire and a larger breaker? I do not know what the motor is drawing amperage wise as I have no papers on the thing and there is no motor tag either. Thanks for any help.

Greg S    Posted 03-09-2004 at 07:54:59       [Reply]  [No Email]
Look at the motor speed on the name plate. A lot of the small compressors are a "special" 3 horse motor that run at 3750 rpm to get a 5 horse "rating" since electric motors are dependent on rpm as part of the horse power rating.

john    Posted 03-08-2004 at 18:29:00       [Reply]  [Send Email]
yep,sounds like it has been wired for 220 instead of 110

TB    Posted 03-08-2004 at 18:38:57       [Reply]  [No Email]
Verify wireng connections before changing the voltage. Did it come with a manual? What brand and model is it sometimes Manuals can be found online and downloaded.

Bob/Ont    Posted 03-08-2004 at 21:23:23       [Reply]  [Send Email]
Hey Tom, I seem to think it takes about 6 amp per HP on 220 if you take inrush into account. Maybe it needs a boost from the main feed Eh.
Later Bob

Sid    Posted 03-08-2004 at 18:15:43       [Reply]  [No Email]
A friend had a smaller compressor that acted like that once. It turned out that the compressor supposed to have a valve of some kind that opens the compressor and it is free wheeling so that the motor can get started without being under load. Just a suggestion for something else to consider.

Fawteen    Posted 03-08-2004 at 18:29:00       [Reply]  [No Email]
Yup, it's called an "unloader valve", drops pressure at the compressor head after the motor stops.

Shouldn't be missing if the compressor is new, but may be faulty.

Sid    Posted 03-08-2004 at 18:15:20       [Reply]  [No Email]
A friend had a smaller compressor that acted like that once. It turned out that the compressor supposed to have a valve of some kind that opens the compressor and it is free wheeling so that the motor can get started without being under load. Just a suggestion for something else to consider.

Dave Smith    Posted 03-08-2004 at 18:11:08       [Reply]  [Send Email]
Diesel, One horse power equals 746 watts times 5 equals 3730 watts divided by 110 equals 33.9 amps. Don't even think about using #12 wire for that or you will have a fire. If you can change it over to 220 volt it will draw 16.9 amps. With a load start up that is still pushing a #12 wire. Go to 220 volts and at least a #10 wire. A #8 would be better. Most motors can be wired for 110 or 220 volt it's just a mater of changing a couple of leads under the cover. There should be a diagram on the underside of the cover. Make sure you get the rotation right. That is a matter of switching leads also.
Dave <*)))><

Craig    Posted 03-09-2004 at 20:31:21       [Reply]  [No Email]
even though it says 5 HP, it is probably not. if it has a plug on it
that can be plugged into a standard outlet, it should run on a
standard outlet. the motor is only 1.5 HP. the manufacturers
were just sued over this, and if you are the origional purchaser
you may be entitled to $50 in free accessories because of the
false advertising. go to and click
on frequently asked questions.

as for why it trips the breaker, i would agree about the unloader
valve not working. when the compressor reaches high pressure
and shuts off, you should hear a hissing sound. this is the
unloader valve releasing pressure from the pump so that it will
be able to start. if you don't hear this, there may be a problem
with the valve

Willy-N    Posted 03-08-2004 at 20:18:55       [Reply]  [No Email]
Daves right and a 5 hp motor should have a fused disconect and a starter to protect the motor with heaters sized to the hp and type of motor. Wiring should be sized for 125% of the running load and it should have motor rated fuses 125% to 150% max depending on the motor rating class. Mark H.

Fawteen - OUCH!    Posted 03-08-2004 at 18:31:09       [Reply]  [No Email]
Yer right, of course. I didn't do the math on a 5 horse motor.

Yet another good reason to get the pros to do it, and not rely on amateur Internet Electricians.

Dave Smith, I just found    Posted 03-08-2004 at 18:39:26       [Reply]  [Send Email]
I just found this on the Farmall Cub club site.
If you have bought a new compressor in this time frame you might be eligable for compensation.
Dave <*)))><

Allen Wood    Posted 03-15-2004 at 10:09:13       [Reply]  [Send Email]
I have two air compressers, one large one and one small one bought after 1997.

allen    Posted 03-14-2004 at 01:19:49       [Reply]  [Send Email]
please add me to the list as i purchased a coleman serial#1083439 yr2001 april 2001 big mistake purchased for auto repair switches died 3mo guages both within 6mo. not enough power to run air tools thank you allen sonnet performance auto and marine calif.

David Goodwin    Posted 03-13-2004 at 22:39:49       [Reply]  [Send Email]
Bought it in December, 1996

paul mcloemore    Posted 03-13-2004 at 07:25:07       [Reply]  [Send Email]

Dave Smith    Posted 03-13-2004 at 09:10:45       [Reply]  [Send Email]
I can't help you with that. I don't know where is would be.
I also bought a Ingersol Rand 80 gallon 5 HP compressor, but it does not come under this law suit as they changed the rating of it.
You'res may not be covered either. They probably changed the reatings once the law suit was started.
Dave <*)))><

Johnny E. Anderson    Posted 03-12-2004 at 23:40:36       [Reply]  [Send Email]
RE: Air Compressor Litigation.
I am in receipt of a form letter referencing litigation against Campbell-Hausfeld Air Compressors and would appreciate any and all assistance as to serve notice that I wish to be part of the settlement class pertaining to this litigation. I bought a Campbell-Hausfeld air compressor - model #WL611103AJ - within the time frame mentioned in the form letter. Please advise.

Dave Smith    Posted 03-13-2004 at 03:19:54       [Reply]  [Send Email]
Go to the link. It has a place to apply if it is the one you bought.
Dave <*)))><

BOSS    Posted 03-08-2004 at 17:46:09       [Reply]  [No Email]
The problem is that when an air compressor starts, it triples the amps. when it has the amp number, that means running amps. Not start up amps.

Look at the running amp # and then triple it.

TO35    Posted 03-08-2004 at 17:41:09       [Reply]  [No Email]
Big D....I have a small comp sitting in the corner and I went to look at it, it's on a 30amp breaker and wire is 10/2 romex. If I remeber correctly mine did the same thing a few years ago and it wound up being one bad capacitor.

hope this helps...

Fawteen    Posted 03-08-2004 at 17:40:28       [Reply]  [No Email]
Yes they make a slo-blow breaker.

No, the capacitors (unless one is shorted) shouldn't affect it, in fact they should REDUCE starting current draw.

Yes, undersized wiring will cause the problem. A 5 horse compressor should be on #12 wire minimum, and I have mine on #10.


Fawteen - Also    Posted 03-08-2004 at 17:44:14       [Reply]  [No Email]
If you go with #12, the compressor should be the only thing on the circuit, and the run should be as short as possible.

Same for #10, actually...

TB    Posted 03-08-2004 at 17:36:16       [Reply]  [No Email]
Look inside the Moter end cap see if it can be changed to 220V. Should be a digram under the cover.

TB    Posted 03-08-2004 at 17:39:05       [Reply]  [No Email]
It should also say on the moter spec plate if it says 120/220 Volts it can be done.

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