Breaker trips with no load

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Old 12-12-09, 05:56 AM
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Breaker trips with no load

I need some help diagnosing a problem I'm having.

We had some ceiling fans put in last year, and the circuit they are on have recently started tripping. They have never caused a problem before. The ceiling fans are the only thing on the circuit.

There are 4 ceiling fans, and the circuit will trip in the middle of the night or during the day when nobody is home. This seems very odd to me. It can't be an overloaded circuit, because nothing is turned on.

The entie job was done in conduit with 12 guage wire and a 15 amp breaker.

Here is what I am going to check. Am I missing anything?
- Loose screw in breaker panel
- Loose connections in switch boxes
- Bad connections in the fan junction boxes

Can cold cause this issue? It has become very cold lately, and part of the conduit runs through our garage.

The run distance to the attic is fairly long. Can this cause an issue?

Thanks for any help.
Scott
 
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Old 12-12-09, 06:47 AM
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Sounds like a bad breaker to me,weird it doesn't trip as soon as you reset it though.You can try taking the wire off the breaker(although you should have a qualified electrician do it,for safety )then reset it to the on position.If it trips with no wire on it then you know it's the breaker.
Try that and we'll take it from there.
 
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Old 12-12-09, 07:15 AM
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Since you also have metallic conduit you should check to see if any of the insulation missing and the conductor is touching the conduit or close to touching.
 
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Old 12-12-09, 08:48 AM
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Thanks for the quick replies. I will try the suggestions and report back.
 
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Old 12-12-09, 09:15 AM
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Does copper wire shrink more when cold than the metal of electrical conduit?

Metal shrinks when cold, expands when hot.

Perhaps the wires were run tight at both ends of the conduit and bent at each end. Then the conduit remains the same size in length, but the copper wire shrinks, then this causes the wire to rub against a piece of sharp metal at the bends in the wiring at either end, then short to ground?

Just a wild guess on my part! I do know with plumbing they need to allow for expansion and contraction of pipes as they shrink/expand with temperature changes.
 
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Old 12-12-09, 09:24 AM
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I think if the wires were exposed at any point,he would have a dead short and the breaker would never reset.If he knows for sure there's absolutely nothing else on the circuit and it trips while nothing is on,it's definitely the breaker.
The fact they ran #12 wire and connected it to a fifteen amp breaker is interesting,unless they were just going with what they had.
 
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Old 12-12-09, 10:07 AM
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Is this a standard breaker or is it an AFCI breaker?
 
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Old 12-12-09, 12:47 PM
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Originally Posted by pcboss View Post
Since you also have metallic conduit you should check to see if any of the insulation missing and the conductor is touching the conduit or close to touching.
You have my vote. May have been damaged when the wire was pulled originally. And this could be tested with a meter to prove it (of course, if it is doing it at the time).
 
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Old 12-12-09, 06:02 PM
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Wouldn't the breaker trip immediately if there was damaged insulation touching conduit? If there is no load on the box, how would there be enough heat generated to trip the circuit if it was just close to the conduit?

I've had the wire out of the breaker and the breaker on for the last 9 hours. The breaker still hasn't tripped. I will check again in the morning. If it still hasn't tripped, I will begin to check all of the junction boxes for exposed wiring or burnt spots.

I am also going to try and switch the wire with another breaker to see if the ceiling fans trip the new breaker.

How would a meter test for damaged insulation?
 
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Old 12-12-09, 06:18 PM
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Old 12-13-09, 08:45 AM
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Okay, I think I may have found the problem. I was in my son's room looking at a junction box in there. When I wiggled one of the wires, a drop of water came out of the conduit that was running up to the attic.

The heat from the house and the wires must be interacting with the coldness of the attic and causing condensation. I will put extra insulation on top of each of the junction boxes to see if that fixes the problem.

Is this a common issue?
 
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Old 12-14-09, 07:56 AM
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Okay, I think the problem is solved. I put great stuff around the back and sides of the junction boxes and a pile of insulation on top of them. I also wrapped the wire nuts with electric tape to keep out any drops of water. The circuit has been on for 15 hours without tripping.

When I get home from work tonight, I will check the boxes again to make sure there isn't any condensation.

Is this a common issue? Should the boxes need to be covered with insulation?
 
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Old 12-14-09, 08:06 AM
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Conduits exposed to different temperatures should be sealed. Sounds like the conduit was acting like a chimney and allowing warm moist air to rise until it hit the cold area and condensed.
 
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Old 12-14-09, 09:42 AM
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Okay, maybe a newbie question, but how do I seal the conduit?
 
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Old 12-14-09, 09:49 AM
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Ductseal which is like a black plastic play-doh can be placed around the end of the conduit and wires.
 
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Old 12-14-09, 10:48 AM
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The Duct seal I use is gray so you may want to look for that as well. You will find it by the rest of the electrical supplys.
 
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Old 12-14-09, 12:16 PM
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Originally Posted by Tolyn Ironhand View Post
Is this a standard breaker or is it an AFCI breaker?
I think you asked the right question...this would be more likely than a normal breaker tripping with the moisture description the poster made.
 
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