Campbell Hausfeld air compressor trips breaker after a couple cycles.

by Robert
(Fresno,California)

My compressor trips breaker after a couple cycles. It's a 5 year old, 5HP 20 Gallon. Checked Unloader valve and it works. Put amp meter on circuit and it pulls 55 amps at start up and settles down to 13 to 15 amps after it gets going. Changed start capacitor and still pulls same amps at start up. Voltage drops to 70 to 80 volts at start up also. Can't seem to find a good print on motor to be able to megger it without having to take motor apart to get to motor windings. I have it on dedicated 20 amp circuit and I tripped breaker while it was filling, waited a minute and reset breaker. Motor started to turn very slowly and tripped breaker. Now should Unloader valve have released air from compressor when I tripped breaker?

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Bill says...

Robert, the opening of the unloader valve is normally a function of the pressure switch reacting to the pressure level reaching cut out. When the pressure switch flips to cut off the power to the motor, it also often toggles an external lever that opens the unloader valve.

Therefore, the unloader valve may not have opened when the breaker blew, and that may be why it lugs on start up.

Is it tripping the breaker "after a couple of cycles" on start up or cut out? If so, that's symptomatic of a pressure switch issue.

Cheers,

Bill