Air compressor won't start

by Steve Dillman
(Fort Wayne IN)

My Ingersoll Rand 5hp230V single phase two stage compressor won't start. Has been in production for 5 1/2 years with no problems. Came into shop and found it caused the dedicated breaker to trip. I reset and buzzing noise at compressor caused me to shut it off. I installed a new pressure switch and problem did not change. I can manually turn the flywheel. I took off the belt to motor and with juice turned on , it powers up and turns just fine. I tore the motor( mechanical pump) off and everything seems fine. No problem with pistons , cylinders or shaft. I don't want to press bearings out unless that seems like the solution.
Any ideas before I reassemble? I didn't fix anything during the teardown, so I assume the problem is still there.

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Bill says...

In order for your compressor to start with any kind of load, the motor needs a boost from an electrical starter or capacitor.

The buzzing sound suggests to me that it's this part of the motor start process that has failed.

Without the starter / capacitor, if there is any load, when the motor tries to start, it pulls more amps than the circuit has available, and pops the breaker.

That's where I would look next.

Cheers,

Bill