Air Compressor Trips Overload

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I used the compressor most of the day last week, shut it off, and the next day it wouldn't even kick on. I got it out a couple days ago and chased power back to the motor, it's a 5hp 230v motor. I'm getting power on both legs at the motor, and continuity on all the grounds. I reset the red overload button and it will kick on, but within 20-30 seconds it kicks back off. The motor is warm to the touch but not excessively hot.

I took the motor off, took it apart and it was fairly clean, not much dust in it at all. All the wire connections look good, no broken or corroded wire contacts. Got the motor back together, and hooked it back up to power...it will run forever without a belt/load on it. I left it running for about 10 minutes and took a coffee break, came back it was still going. I changed the oil in the compressor, put the belt back on, and 20 seconds later the red overload button tripped on the side of the motor. I have to wait a few seconds to trip the reset button, but it will come back on, only builds up 10 psi or so before it kicks back off.

[zoe60]

See if you can check the current with an Amprobe while it's running. The compressor could have a problem and put too much load on the motor. There will be an amps rating on the label on the motor. If it is 120/240v go by the lower current rating since it runs on 220. If the current is OK the reset may be bad. If not look for compressor problems. Also check it with the belt off for comparison.

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I did run it with the belt off, it runs fine without a load. The compressor feels like it used to, so I'm not sure what failed.

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My snap on 230 volt gave me fits. If the length of wiring from the breaker box is more than 20 feet or so , use wire that is bigger. I am not an electrician but I did wire my shop. It seems I had to go from 14 gauge to 12, or 12 to 10, something like that. The reason is the voltage drops too much and the amps go up.

The next thing I found was some of the wire ends were not on good and the connection got hot, same result. Next the breaker started getting hot, probably because I tripped it so many times figuring it out but after a new one of those all has worked well.

My model of snap on I think was made for them by a company called Big Red. Really nice iron but their wiring sucked!!

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I dunno, the thing has worked great where it sits for the last couple years. The wires aren't very long, maybe 5' or so. The main breaker isn't tripping either, a buddy told me today it could be one of the capacitor deals mounted on the top. I'm gonna google and see if there's a way to check those and go from there.

[Movin]

Check all the connections on the unit at the switch, the breaker and the pressure switch. Something is likely getting hot running. Caps only are used for start up.
Watch it in the dark, maybe you have an intermittent short.

[zoe60]

It could have a run capacitor too. See if there are two capacitors. Run capacitors are usually oval shaped and made of metal. Start caps are usually black and plastic. It would really help to check the current both under load and with the belt off. I used to work in an electric motor shop and running current is a valuable trouble shooting measurement. See if you can borrow an Amprobe. Just clip it around one of the wires and see what it reads. Since it is starting OK I don't think it will be a problem with the start switch, centrfugal switch, or the start capacitor.