Slow tripping breaker

phishfud

Just had my electric service upgraded a few months ago to 200A. I have an air compressor in my garage that I just hooked up, and even though it doesn't trip when starting or running, I've noticed the breaker being tripped many many hours later, when the compressor was set to off, and would not be needing or using any draw at all. It's the only thing on this circuit. As per my electrician, I ran 10-3 wire (only cause it was left over from doing my service), using only the black, red and ground. White is capped at both ends. Compressor says the motor is 240v/15a. I used a 20A double pole breaker. Anyone have some insight as to why this breaker is slowly tripping when there is no load on it? Bad breaker maybe? Or should I have used a 30A? Any advice would be appreciated.

joecaption

There has to be something wrong with that breaker or the wiring if there is no known load on it and it trips.
Did you install a twist loc plug or hard wire it? If it's just pluged in then unplug it and see if it still trips.

Julius793

Something wrong in the line such as loose wire, nicked wire or something else.

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Yoyizit

Not ranked in order of likelihood:

-a loose connection nearby in the panel busbars is causing this particular breaker to heat up and trip
-the breaker has an internal, possibly factory, defect that causes it to trip at random whether carrying current or not
-the breaker was damaged by an internal, perhaps intermittent, defect in the compressor
-both this particular breaker and this particular compressor were OK but 'they do not get along with each other' and now this breaker is damaged. This is extremely unlikely.
-some combination of one or more of each thing that was mentioned in this thread and this post

I'd look for patterns in the breaker tripping over the next several days with the compressor in use or not.

phishfud

I appreciate the responses. There is no plug, just it hardwired to the box. I'll keep an eye on it and double check for loose connections. Worst case is I'll try another breaker if the connections seem ok. Anyone think maybe I should have used a 30A breaker instead of 20? Thanks for the help.

fa_f3_20

I'd get a clamp-on ammeter and check the circuit when the compressor is off. If current is flowing, then obviously there's a problem somewhere.

Another possibility is that something in the panel adjacent to the breaker is getting very hot -- either another breaker, or the busbar. Next time the breaker trips, run your hand over the faces of the breakers and see if anything feels unusually warm.

Missouri Bound

How are you turning the compressor off? Are you sure it isn't trying to start when you aren't there? If it's not off and it trips the breaker when tryhing to start, the unloader could be an issue. Does it ever trip when you are using it and it restarts?

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rrolleston

I would fallow the wire and look for bad spots or really tight staples turn off and double check all connections in compressor. Maybe wire nut the supply wires inside the compressor without the compressor wires connected and turn the breaker on and see if it trips.

dmxtothemax

There is such a thing as a slow blow breaker !
I think they are called type two !
They are dsigned for loads such as motors that
pull a large start up surge, and then settle down.

Your breaker could be one of these,
Or it could just be plain faulty !
Are you sure it is not running close
to its maximum limit, amp wise ?

mpoulton

Those breakers only trip after an extended time under excessive load. They won't trip AFTER the load has been turned off, which is what he's describing.

dmxtothemax

Either the breaker is faulty !
Or there is a bad neutral somewhere,
causing currants to be there that should not be there !

either put am ammeter on it ?
Or call a good electricain !