Latest Discussions : Electrical & Lighting


08:46PM | 05/16/05
Member Since: 05/16/05
1 lifetime posts

I have a Harbor Freight air compressor which is stated to run at 16 amps. In my garage, there is a 20 amp GFI outlet, and the circuit breaker to my garage is also 20 amps. Nothing else is running on this circuit, or even plugged in.

When I initially ran the air compressor, it would trip my circuit breaker. It runs for a minute or two, and then it'll trip the breaker. I would have to reset both the breaker and the GFI.

I replaced the GFI one with another 20 amp GFI from **********. This time, after a minute or two, it would trip just the circuit breaker.

Is there anything I can do to fix this? Can I easily replace a circuit breaker myself? Is this even the problem? could the circuit breaker be bad?

I've run 15 amp toosl on it, and it never trips the breaker. This 16 amp air compressor trips it though...

I started it up and


06:48AM | 05/17/05
Member Since: 04/25/05
1915 lifetime posts
Motors can draw 6-8 times there normal full load current when starting. Specially for compressors.

However, breakers work don't tripp the instant the current is more than 20.1 amps. They work on an inverse time delay that allow them to the supply an large amount of current for a short period of time.

First check if the Unloader is working on the compressor. If you have not been able to run it long enough to get it up to pressure then this won't be a factor. If it runs sometimes to full pressure, when it stop you should hear a short hiss. This releives the pressure from the tank to the compressor head so that the motor does not have to fight that pressure until it is upto speed.

If that is not applicable then you can try replacing the breaker. They will often get old and trip at lower currents.

In most cases that is simple to do. Post the brand and model of the panel.

Your other option would be a dedicated circuit for the compressor. That allows you to use special rules for sizing the breaker.

However, HF products, will functional, or often fairly low quality and they stretch the specs and might be bad out of the box.


02:31PM | 05/17/05
Member Since: 05/03/05
79 lifetime posts
Here's something to try.

Plug the compressor into your laundry outlet. Usually the laundry outlet is a 20Amp circuit. IF the compressor trips that breaker I would return the compressor.

If it doesn't trip the breaker, your garage breaker may be bad/weak.

What yo udidn't mention was lighting in the garage. Are the lights on the same circuit? What kind and how many lights? Attached or detached garage?

Just a few thoughts.


02:38PM | 05/17/05
Member Since: 05/03/05
79 lifetime posts
Forgot to ask--What is horsepower of compressor?


03:29PM | 05/17/05
Member Since: 04/25/05
1915 lifetime posts
FTW, consumer grade air compressors follow the "rating" of shop vacs, even thougth they are induction motors.

It might have HP tag on the compressor for something like 5 or 6 hp.

On the motor label it will have the current and voltage specs, but the HP column will be marked "SPL" (special).

So HP numbers are meaningless for sizng the breaker.


03:29PM | 05/17/05
Member Since: 04/25/05
1915 lifetime posts
FTW, consumer grade air compressors follow the "rating" of shop vacs, even thougth they are induction motors.

It might have HP tag on the compressor for something like 5 or 6 hp.

On the motor label it will have the current and voltage specs, but the HP column will be marked "SPL" (special).

So HP numbers are meaningless for sizng the breaker.


08:41AM | 05/26/05
Member Since: 05/24/05
6 lifetime posts
How far away is the compressor from the circuit breaker. In the field we have had some trouble tripping bkrs with chop saws. We did everything checked all cnnections even placed a clamp on on the circuit. We found that if we locate the unit closer the the source the problem is eliminated. So my question again is how far away from your bkr is the unit?


10:38AM | 04/30/13
Make sure to check the shop vacs for the various types. The induction motors will have to be checked as well. If the compressor rating is at 5 or 6 hp then you might need to do a replacement. I suggest cutler hammer. If you need to change it with a new circuit breaker then do so, better now than later. Also try checking the amps against some tech data sheets to make sure they're correct. The distance also matters between the compressor and breaker itself.


07:13AM | 12/03/17
My air compressor trips the circuit breaker if I set a wider cut in and out pressure range. I am using Condor MDR3 pressure switch.
After i turn on the circuit breaker the compressor will continue pumping until kick out pressure without issue.
If the cut in and out pressure range is set narrower the compressor will not trip.
I am using Atlas Copco compressor.
Kindly advise what would be the possible cause of the problem.


08:35AM | 05/06/19
If your GFI is properly installed with the line and load placed in the right locations it shouldn't pass that GFI and trip the breaker in the panel. Also you can tell if it's installed properly by the fact that you can reset the GFI itself. You might also have no ground on that at all or somewhere along the series of plugs between that GFI in the panel a ground was not properly hooked up and that's creating the problem with it not tripping the GFI. Hope that helps.


09:30PM | 10/03/19
I’m having a similar problem. I have an 8 gallon 1.8hp. It fills to full compression, but then the Motor makes buzzing/strained sound and trips my outlet.

Any ideas?



01:59PM | 01/12/20
I inherited my father-in-law's air compressor he used in his dental practice. It works well in summertime but trips the breaker in cooler weather. I moved to another house and the exact same problem arose, works fine in summertime, trips the breaker in winter. It is located in my garage. Any hints?


04:46PM | 05/04/20
I had a problem where my 21 gallon HF compressor would only run about 30 sec. before tripping the on-board breaker never going above 50 PSI. I had replaced the original oil and put in the correct amount of new oil. It look like it was just to the fill line, but apparently, its difficult to get all of the old oil out and the fill line is not very accurate to the eyeball. I solved this problem by draining about 2 ounces of oil from the case. On the next start it went directly to 125 PSI.


02:29PM | 11/28/20
My would run fine when it was warm, but trip the breaker when it was cold. I drained a little oil, at BV022321's suggestion, then opened the valve and just let the compressor engine run for about ten minutes to let it warm up. Closed the valve and it pressurized great.


03:56PM | 01/19/21
I had an old 15 Gal 3.5 HP Craftsman air compressor with the same issue. I changed the capacitor and pressure switch but it doesn't fix the issue.

I tried to drain out 300cc oil at BV022321's suggestion. It doesn't work well immediately, but after a couple of days it works perfectly now.


09:13AM | 08/30/21
My DeVilbiss PAF430 begins to spin and pops the breaker. I moved to a less loaded circuit. It ran 3 seconds longer then popped the breaker. >There is no preexisting tank pressure, so I think an unloader circuit wouldn't be an issue.
>I took the motor cover off and test spun the motor/pump. Moves freely.
>I tested what I could with a VOM on the switch. Seems to function normally.

Not quite certain what is going on...


02:47PM | 11/08/21
INHERITED A SEARS 1HP, 12GAL.AIR COMPRESSOR. NEVER HAD A COMPRESSOR THIS LARGE ( WHEELS WITH A NICE HANDLE ) I used to just plug in my old small round compressor with a 50ft electrical cord to blow out my sprinklers ( 100psi max ) Tried the same thing with the larger on, it started but within a minute it stoped (tripped the breaker ) THIS WAS AN OUTSIDE OUTLET. DO I NEED TO FIND A DIFERENT OUTLET THAT HAS A HIGHER AMP # ? PLUS GET RID OF THE EXTENTION CORD, AND USE A 10GA CORD?

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