Starting a 3hp 20 gallon compressor

by Greg

Acting just like a start capacitor.

Gives a half crank and stalls till breaker trips.

I'm leaning towards a start cap.

My only question is that when I disconnect the belt to the motor it starts up and runs fine. Just with a load off the compressor does it do it. Still the start cap??
Can't be sure as I don't have enough info to decide.

Tell me about the power supply. 120 VAC? Extension cord? Breaker amperage? Age of compressor? What ambient temperature is when you are trying to start the compressor? Will the compressor start and run OK with the tank empty?

Sure, could be the start cap, but could be other things that cause your compressor to start and pop the breaker.


Comments for Starting a 3hp 20 gallon compressor

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Mar 01, 2014
Check valve was the problem
by: Anonymous

It was the check valve. Emptied tank and freed it up. Runs fine now. Condensation in tank. Thanks for help

Feb 28, 2014
Compressor starting problems
by: Greg

It's an older sears double piston aluminum head 120vac 20 gallon. Back when they made them good. I just read the start caps out and they read good. Motor runs fine when belt removed. Cranking the wheel by hand has resistance when pistons compress. Even with the tank empty. Weird squeak out of check valve. Ambient is really cold. Thinking check valve stuck. Gonna check this weekend.
Maybe, that's worthwhile checking. Does your truck start easy when it's really cold? Mine doesn't, and neither does my air compressor.


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