Air compressor

Anyhow, you might have a weak breaker. You might have 14ga wire. You might be on an extension cord. You might have several lights or other things on this same circut. Any of this will cause your breaker to go. The motor is pulling at least 20 amps to start up. There is no margin for extra load, or poor wire. As well, is the bleed-down working on your compressor, so it starts with no load?

It is possible to get special breakers that allow for electric motor startup loads. Might wish to look into that. So long as you have strong enough (12ga or better) wiring, and no long extension cord or 14 or 12 ga short cord. Even a little cheater plug rated at 15 amp can be enough to set off the breaker. These air compressors on 110v will pull the full 20 amps, you got to have all the wiring right & proper.

--->Paul

You can do a preliminary test on the capacitors (may have 1 or 2) with an ohmmeter which will show if they are totally open or shorted BAD but it wont really tell you if they are good, that takes a capacitance tester. Make sure their wiring connections are all good n tight and you might just take them to a motor shop for testing. If they are bad she could draw heavy start up current that might cause the thermal element of the breaker to trip.

Dont ask me too much more, its been toooo long since I worked with motors and Im a tad rusty n runnin outa smarts here lol

John T

1) make sure that the compressor unloader is dumping the pressure on the pump head at shutdown, which is not happening automatically if the unit dies before the pressure switch shuts it off. At the pressure switch is a button or lever, turning it off or pushing the button will dump the head pressure, and allow the pump to start up without a load on it. Listen for air rushing out when you operate the button/lever to off.

2) while published as 6 hp, you indeed have a motor that is about 1-1/2 hp RUNNING, and 6 hp STARTING. Funny how many people don't understand the difference. In any case, most portable compressors are mis-advertised by their running hp and most stationary units are advertised by their actual running hp.

3) You may very well have a centrifugal switch that is not throwing out on start up. The start capacitor is staying in the circuit and the motor wont come up to speed, and the breaker blows. This is an internal motor problem. Some can be fixed without motor disassembly, some are more difficult. A motor shop can easily check this out.

4) If you do not intend to move the compressor and it will stay in one place all of its life, you might be better off running a 20 or 30 amp 240v circuit to where it sits and changing the motor and plug to 240v. If you think you might need to move this unit to a different location, leave it 120v, as you can easily plug it in anywhere. I have a 1-1/2 hp Craftsman about 30 years old. it too has a convertable motor. I have moved it too much over the years to justify changing it over to 240v. I now have a stationary compressor and use this one for odd things like pumping the head charge on the community well tank and such, so it has to be 120v or it would be useless to me.

Charles

2) while published as 6 hp, you indeed have a motor that is about 1-1/2 hp RUNNING, and 6 hp STARTING. Funny how many people don't understand the difference. In any case, most portable compressors are mis-advertised by their STARTING hp and most stationary units are advertised by their actual running hp

Charles

I seriously doubt thats a true 5 hp motor, if so its full load current would be like 56 amps at 120 volt or 28 amps at 240. If that were the case (which I doubt) you would have to feed it with like No 8 wire and may have to use a 50 amp breaker to allow it to start without tripping the breaker on startup. A 1 HP motor at 120 would draw 16 amps.

Better use an ammeter and then have a motor shop test the motor n start circuit for RPM drop out and the capacitors and thennnnn nnn re wire it for 240 volt operation.

John T Retired Electrical Engineer

www.oldduggy.com (my blog)

Well the specs call for 15 amps at 120 v.
Ever consider that the reason it was sold is that it was tripping breakers.
You did say it was used.

Might want to take the motor off and have it checked out.

Runs great on a 20amp breaker at 120 volts. Its run as long as 45 minutes continuously. Never tripped the breaker.

I agree and would suspect a problem with the motor, or a very weak breaker.

• Hobby farm

5 hp on my quincy says 29 amps on 230 v , double that for 110 v .

Allow at least 1/2 again preferably double that for starting current.

george