I'm in the process of setting up my air compressor in my new shop. Ran the main line weeks ago and dead-ended it in the approximate area the compressor was gonna go. 6/3 with ground, hooked to a 30 amp 2 pole breaker.

Got the compressor placed yesterday, wired up the motor starter today. Flipped the breaker on, flipped the start switch and....nada. Da Fuq? Flipped the breaker off and back on just to be sure it was on. Nada.

Went back to the compressor room and verified that the connections on the motor starter were correct and tight. All good, that's not it. Hmmmm.

Got my meter and check voltages at the motor starter. Red leg, 120V to ground - good. Black leg, some insignificant value. Hmmmmm.

Went back to the panel and checked at the breaker. Same results, hot on red, nada on black. Da Fuq? Bad breaker?

Killed the main, disconnected the leads at the bad breaker, disconnected the leads at the welder breaker and swapped the welder breaker into the air compressor breaker position. Et Voila! Power! Compressor starts and runs like it should. Cool, bad breaker. That happens, especially these days.

Popped the bad breaker in the welder position just so I wouldn't have hot lugs exposed in the panel with the cover on. Just for gits and shiggles, I checked the power again and...WTH? Both sides are hot. Hooked the leads back up for the welder outlet and plugged a welder in...all good.

I'm very confused.

Still gonna replace it just because I don't need/want a 50 amp breaker on the compressor.

What happens when you swap the breakers back into their original position?

Breaker probably had a poor connection where it contacts the bus bar. In the process of swapping them, you probably obtained better contact.

quote:

Originally posted by sigcrazy7:
Breaker probably had a poor connection where it contacts the bus bar. In the process of swapping them, you probably obtained better contact.

Didn't mention it, but I removed/reseated the breaker a couple of times thinking that same thing.

I may try swapping them back and seeing if it still works.

Might have burned contacts on the breaker. Replace it. Then take apart the bad one to see how it works.

Didn't think to mention, it's a brand new breaker in a brand new box.

But yeah, it's getting replaced.

Did you happen to measure the voltage at the breaker after the compressor wiring was unhooked?