air compressor motor starting
by Tim
(St. Louis, MO)
I have a craftsman air compressor that is 5.5hp 120 volts. It is plugged in to a dedicated 20 amp 120 volt circuit directly off a circuit breaker box on a utility pole When the air compressor is turned on, it attempts to start but trips out the 20 amp breaker. The breaker is new. The compressor operation manual says it will start and run on a 20 amp circuit. I have checked the air pressure check valve and it is not stuck. Is the motor starter, assuming it has one, maybe bad ? The compressor has been used inside and is about 5 years old and used very little. Moisture has been drained from the tank regularly. Any advise on what might be the problem with it not starting ? Thanks in advance for your help. It is appreciated.
Bill says...
Hello Tim:
Do you recall if the compressor unloaded the last time it ran?
It sounds to me as though the unloader valve may not have functioned, there's air trapped over the piston, and when the compressor motor tries to start, the added load of that trapped air increased the motor demand beyond the capability of your supply circuit.
Cheers,
Bill
