compressor starts but trips breaker

6 years 3 months ago - 6 years 3 months ago #2292 by pbklna
compressor starts but trips breaker was created by pbklna
hey guys puzzled here.
919167341
I have a Craftsman air compressor 6 horsepower 33 gallon tank. I tested the start and run caps with ohms and capacitance and both are good, and have no visual damage either, no bulging or leaking.
The Run cap was rated for 30uf and it registered 29 UF with a plus or minus 5 variance the start cap also measured within its range.
Isolated the compressor on its own 20amp circuit direct from the panel under 10 feet away, nothing else on the circuit.
Its indoors and and issue started in warmer weather as well.
When I turn the compressor on it kicks over and sounds like it's struggling to start to run and then pops the panel breaker. The compressor doesnot have a reset button. The fan wheel is free and can move easily.
The tank is empty with no pressure and the valve is out.
Also had disconnected the line from the pump going to the take to relieve all pressure to the head and when it tries to start I can feel it trying to push pressure out but still trips the breaker. I bypass the pressure switch and same thing happens still trips the breaker. Anyone have any other thoughts thanks

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6 years 3 months ago #2293 by MTR-Admin
Replied by MTR-Admin on topic compressor starts but trips breaker
Thanks for the post!

It sounds like a bit of a conundrum, being your tank is empty (that rules out back-pressure) and you tested the capacitors (which appear to be in good shape).

Typically I would say your start cap is defective, but based on your test we can rule that out.

The only other obvious (potential) issue would be the motor starter switch. It may be slightly corroded, therefore the contact aren't able to make contact.

You can find out how to clean the motor starter switch by clicking on the below link:
www.mastertoolrepair.com/images/How_To_C...r_Starter_Switch.pdf

Also, make sure the belt isn't too tight or loose; there should be a 1/2" deflection when you press down on the center point.

- MTR

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