Compressor won't start. and blows the breaker.

by harold
(tucson az)

It has a 7 1/2 hp motor 230 1ph.

When we first wired it up the compressor worked fine but after two days it won't start.

We replaced the contactor but still nothing.

It wants to then blows the breaker.

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Bill ponders...

Hi Harold...how're things in Tucson, bum compressors aside, of course. :-)

I don't know what your brand of compressor is, nor do I know what type, but I'm guessing it's a reciprocating compressor...one with piston(s)?

That being the case, when you last had it working, did it "unload" when it reached the high pressure cut-out?

That it's popping breakers when it tries to start tells me that something is pulling more amps than the breaker can handle.

That could be a ground fault, a short, or there aren't enough amps in the breaker to supply enough electrical power to turn your electric motor over against high pressure trapped over the piston when the compressor last stopped.

That air is supposed to bleed off to atmosphere when the compressor reaches high-pressure cut-out. That's the characteristic "pssshhhhhht" you hear when the compressor stops.

If your unloader valve is pooched, or the pressure switch has a problem, then that might pop your breaker.

With the information you've provided, there's my best guest.

Cheers,

Bill