Motor first turns for a few sec then the breaker kicks,
by pat nelson
(rochester, ny)
Motor first turns for a few sec then the breaker kicks, its a small craftsman air compressor 4hp, i took the motor off the compressor and took it apart, didnt see anything wrong to the eye. sprayed it with some elec contact, tried it again and it starts for a few sec and then blows.
Bill says...
Hello Pat, thanks for writing in about your compressor blowing your breaker.
It's hard to be sure without actually seeing the scenario unfold, yet I think you may have a problem with your unloader valve not being operated with the pressure switch.
It dumps the air over the cylinder when the compressor shuts off, making it easier for the compressor to restart when cut in pressure is reached.
If the unloader valve hasn't relieved the air, the motor tries to start, draws too many amps as it tries to overcome the pressure already on the piston, and this blows the breaker.
The unloader valve is probably on the side of your pressure switch, and it may be a paddle that pushes on a valve stem. Can you push that valve stem yourself? Does air come out? If so, then try to restart your compressor and see what happens.
When the pressure in the tank reaches cut out, the pressure switch opens the contact cutting electricity to the motor, and at the same time operates the unloader valve. If that isn't happening, then the next time the compressor goes to start, that might cause the breaker to blow.
Good luck, and maybe let us all know how this worked?
Cheers,
Bill
