15a Breaker (seemingly) randomly tripping

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Old 01-22-14, 08:24 AM
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15a Breaker (seemingly) randomly tripping

Ok, I've isolated the part of this circuit which I believe is causing this. I will run down the scenario:

1) Tuesday night a 15a breaker tripped.
2) I reset the breaker and it tripped immediately so I began with process of elimination and I turned the lights off in one bedroom.
3) reset the breaker and all is well so I go to that room and turn the light switch on and the lights come on but I notice that the dimmer is not working now. before I go any further, let me explain the circuit.

There are other lights in other rooms on this circuit but it seems the problem is in this room. This room has power to the switch, then it goes up into the attic and splits to (4) recessed lights (which have been installed and working fine for months). The cans each have an LED indoor spotlight bulb.

I assumed that because the dimmer function of the switch no longer worked, I simply had a bad switch that was shorting out so I replaced it with a simple on/off switch. Same problem only this time it took a few minutes for the breaker to trip.

Now what I did was just leave the light switch off for several hours and the breaker did not trip. At this point I am sold that the problem is downstream of the switch. So, I unscrewed 3 of 4 bulbs in that ceiling and turned the switch on. The breaker never tripped. Screw in 1 more bulb, breaker trips within minutes.

Thought there may be an issue with the bulbs so swapped out all (4) LED bulbs for CFL. breaker trips immediately.

Went into the attic to examine the wiring connections at the lights and everything looks normal. Nothing appears burnt or otherwise. Turn the lights on and they remained on for a couple hours. now this morning my wife sends me a text saying that the lights don't work.

I'm lost. If the breaker trips, there must be a short right? If there's a short, why does the breaker trip immediately sometimes, 5 minutes another and hours later other times?

Could the breaker be bad?
 
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Old 01-22-14, 08:34 AM
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Could the breaker be bad?
Simple way to test is swap the wire on that breaker with a wire on a breaker of the same size. If the "new" breaker doesn't trip then you can be reasonably sure it is the breaker.

However it sounds more like a circuit loaded to almost maximum that eventually trips as heat builds up. The fact that CFLs with perhaps slightly higher power requirements trip it quicker seems to support that guess. A brand new breaker may hold longer but the ultimate fix if overloaded is to split the circuit.
 
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Old 01-22-14, 08:39 AM
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Thanks for the reply!

That's what confuses me though Ray. Sometimes it pops instantly but last night, it ran with all CFL bulbs for hours.

Couple that with the fact that I modified this circuit months ago when I added the high hats and never had a problem until now. That's what makes this so darn weird.

The room originally had a standard fixture in the center of the ceiling. I just got rid of that and ran power from it to one can and daisy chained to the others. Wonder if I might pick up an amp clamp and have a look. I think I will switch the breakers out though just to rule that out.

Other odd part is that the dimmer switch broke. It's pretty new. Its a C-L that I picked up when I did the original LED/ high hat install.

 
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Old 01-22-14, 09:23 AM
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The key might be how heavily loaded the circuit was before the new load was added.

When a breaker trips from overload the insides will not reset until it has cooled enough to allow the contacts to close.
 
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Old 01-22-14, 09:36 AM
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Speaking of load, does it take a while to build up? or is it instant?

I guess I'm mostly perplexed with the fact that everything worked fine for months. Wonder if the wife plugged something new in, a charger or something.
 
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Old 01-22-14, 10:54 AM
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A depending on the rate a breaker can hold 125% for 2 hours. Higher loads will cause the breaker to trip faster.
 
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Old 01-22-14, 10:56 AM
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Load is instantaneous. Heat takes a while to build up.

Standard breakers are thermal overload protection devices.
 
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Old 01-22-14, 11:46 AM
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Did not know that. I always thought breakers tripped when there power was shorted to ground.
 
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Old 01-22-14, 11:51 AM
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Speaking of load, does it take a while to build up? or is it instant?
A 15 amp breaker carrying 15 amps will take a while to heat up enough to trip. A new intermittent load plugged in somewhere could cause this. You need to identify every load on the breaker. An Amprobe reading of the circuit at the panel might also be helpful in understanding it.
 
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Old 01-22-14, 05:04 PM
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ok, here's a couple curve balls. Came home tonight after the breaker had been tripped ALL DAY today.

I unscrewed 3 of the 4 bulbs and turned the light switch on. I went to the breaker and reset it and it instantly tripped. Remember, this is with the breaker having been tripped all day, so these circuits had been cold for 9 hours. After the breaker tripped instantly, I reset it again and it was fine. Just for fun, I turned it off and on again and in a couple seconds, it tripped. Then, I turned it off and on about 8 or 10 times and left it on. I went upstairs to find the (1) bulb in that room on. All was well. I turned the light switch off and went about my business. My daughter goes up stairs, turns the switch on and poof! breaker tripped. I reset the breaker and this time the lights stayed on for about a minute.

I'm pulling my hair out over here. This has got to be a problem in her room, in those lights - somewhere. But the cans are so simple. And, what could have caused the dimmer function of the dimmer switch to quit working?

This is so weird. What about a bad/loose connection somewhere in one of the light boxes? Or would that just cause the lights to flicker and not necessarily trip the breaker?
 
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Old 01-22-14, 05:13 PM
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I always thought breakers tripped when there power was shorted to ground.
Standard breakers will indeed trip from a dead short. They will also trip from thermal overload.

I'm pulling my hair out over here. This has got to be a problem in her room, in those lights - somewhere. But the cans are so simple. And, what could have caused the dimmer function of the dimmer switch to quit working?

This is so weird. What about a bad/loose connection somewhere in one of the light boxes? Or would that just cause the lights to flicker and not necessarily trip the breaker?
Have you done the test that Ray suggested yet?
Originally Posted by ray2047
Simple way to test is swap the wire on that breaker with a wire on a breaker of the same size. If the "new" breaker doesn't trip then you can be reasonably sure it is the breaker.
 
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Old 01-22-14, 05:15 PM
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It sounds like a dead short and something is moving just enough to make contact with a grounded surface.can you remove the fixture wiring from the house wires and retest?
 
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Old 01-26-14, 12:49 PM
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UPDATE:
I just now had time to climb back into the attic to troubleshoot per pcboss. I opened on of the junction boxes for one of the (4) lights and what I found was WATER! So, because there are no leaks in the roof, this is condensation. (it's been about 15 degrees lately here in MD). So here's the billion dollar question. I have a light fixture that heats up and it's installed in an area that's really cold.

I'm at a stand off with my house. Thoughts?

Something that is weird is that I found condensation in only (2) of those light boxes. I even check some from other rooms - all dry.
 
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Old 01-26-14, 01:33 PM
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You must have a tremendous heat loss into the attic thru those cans. If those aren't the IC type cans then you need to build an enclosure around it in the attic to keep in the heat. Anything built can not touch the cans and must allow for some heating off the can.
 
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Old 01-26-14, 01:44 PM
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These are IC rated 6" remodel housings. There IS insulation in the attic but it's been disturbed in many places. I never thought about that. Wouldn't the fixture itself also get hot due to having a light in it?

Next weekend I'm going to go up and make sure insulation job around those fixtures is top notch. Should there be insulation all around the fixture and above it? So it is sort of buried in the stuff?
 
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