Saylor Beall air compressor trips circuit breaker immediately after starting

by John

Saylor Beall air compressor

Saylor Beall air compressor

Saylor Beall air compressor
Saylor Beall air compressor label
Saylor Beall air compressor capacitors

I have a really perplexing problem with an older air compressor. The compressor is an old 2-stage Saylor Beall 80 gallon with a 240v 5HP Dayton electric motor.

When the compressor is plugged in, the motor starts and begins to turn the compressor pump, but then trips the circuit breaker right away. I have checked the current with an AC clamp meter, and the motor is drawing a peak of 213 amps on startup with the belts hooked up to the compressor.

I have tried unhooking the compressor from the tank so that the compressor head cannot build up pressure. This did not change my results. I still tripped the breaker with the tank unhooked.

If I remove the belts so that the motor is not coupled to the compressor head, the motor will start and run fine, but does make a lot of noise like the bearings may not be in the best shape. When I remove power to the motor, the motor keeps spinning for a LONG time. As the motor spins down, there is a point at which I hear a click and the speed decreases quite suddenly. It's almost as if there is a brake inside the motor that kicks in at this point.

When I hook the belts back up after running the motor by itself as described above, I can start and run the compressor successfully one time. The compressor will run until it reaches the cutout pressure and then shut down. After this one successful run, I cannot start the compressor again without tripping the breaker.

There are three capacitors on top of the electric motor. One is a 25MFD oval cap, and the other two are round 1070MFD. I have tested these with the capacitance function on my AC clamp meter, and they all test OK.

I would greatly appreciate any help, as I am really stumped with this.

Comments for Saylor Beall air compressor trips circuit breaker immediately after starting

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Jul 17, 2012
Circuit breaker tripping
by: Buster

John, I don't know what size the circuit breaker is you are tripping, but by the nameplate on the motor, it should be a minimum of 30 amps, you should only load a breaker to 80% of its rated capacity. It should have at least #12 wire attaching it to the plug also, by the current ratings. The click you hear when the motor is slowing down is the centrifugal switch in the motor that switches the start windings out when the motor starts and accelerates the running speed. The 218 amps you read on start is about right, usually it is about 10 times running amps.
I would change the circuit breaker first and see what happens. You have done some good troubleshooting steps to eliminate some problems, good work. I hope this may help a bit, Let me know.


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