Air Compressor flips breaker
 

I have a 6hp oil free air compressor that keeps tripping the breaker before any pressure is built. I've replaced the starter capacitor and running capacitors, and still flips it. If I take the air supply hose out of the tank, and it will run fine. I appreciate any help!

At the risk of stating the obvious, what amperage is your breaker?

Is it on a tandem breaker?

Not sure that I am following you, but will try. Does the compressor start when the tank is empty, i.e. zero pressure? Does it then pump up to full pressure and shut off? Is it when it tries to restart that the breaker trips? But if you bleed air off through the hose, to lower the pressure in the tank, does it then start? If yes to these questions, and if you have checked your circuit to ensure that it is adequate, as DrHicks recommended, your unloader and/or check valve is probably malfunctioning. The purpose of the unloader is to release head pressure once the compressor shuts off, because the compressor will not turn over if the cylinder is under pressure, and the purpose of the check valve is to allow compresssed air to flow from the cylinder to the tank, while preventing it from flowing back from the tank to the cylinder.

A 6hp, 120VAC compressor probably needs at least 15A, and most likely, closer to 20A to run.

It's on a 15A, and it starts up when the tank is empty, but will not build any pressure before the motor starts to bog down, and then trips the breaker after about 10 seconds of running bogged down. I'm not sure if it's a tandem breaker...
Thanks for all the help so far! Let me know if there's any other information I need to get to help solve this!

Ayuh,... It sounds like an inadequate power supply....

What is the minimum power supply listed on the motor's tag,..??
Ya probably need at least 20amps...

There's your problem. 15A is not adequate to run your compressor. That's the size breaker usually used for lights.

at peak hp, a 6hp motor needs ~37 amps at 120v. (assuming 100 percent efficiency in conversion from HP to KW)

1st, are you sure this isnt a 240v motor (a 20a 240v circuit is pretty common for compressors)<---20a at 240 is = 40a at 120

2nd, yeah, 15a is not even close.

3rd...if it is 120v it is probably not truly 6hp.

Because you said that you changed the capacitors, etc., my initial interpretation was different, in that I erroneously assumed that it had been running, and this problem just popped up. But, since you have now clarified, I agree with the other guys; it is a power problem. And, once you have that addressed, keep in mind that an air compressor should not be run on an extension cord; if you need more reach, buy more air hose.

Excellent point!

I have a 5.5 HP that started doing Sunday power supply hasn't change. 20 2 pole breaker been working the same breaker for 10 year. I think it not switching from the start circuit to the run circuit please feel free to comment not sure

Dusty there is a check value between the compressor and the take it should take the pressure of the compressor head if it fails then u have tank pressure on ur compressor head. It cheap enough I'd recommend doing that

I'm sorry, I just got home and checked, and it is on a 20A. Would that be enough to run this compressor?

A 6 hp compressor? No.

Granted, there might be something else wrong, but if that compressor is as large as you're saying, it will draw a LOT of electricity.