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#36085 03/30/04 10:37 AM
Joined: Jul 2001
Posts: 599
J
JBD Offline
Member
Did the breaker trip before the damaged wire caused a fire? If so, it is not "defective".

Not being able to reset a breaker after multiple trips is not an indication of a defect. UL only requires a breaker to be tested for 2 operations (Close - Trip - Close - Trip) at rated fault levels.
Trivia note: Square D Homeline breakers have the same trip mechanism as their QO breaker line.

Why are we assuming the damaged was entirely caused at this moment in time? Maybe all of the devices had been damaged in the past and the addition of the new wiring/load was simply "the straw that broke the camel's back"?

#36086 03/30/04 04:50 PM
Joined: Feb 2002
Posts: 840
C
Member
deleted because of redundant post

(read the whole darn thread before responding!!!) [Linked Image]

[This message has been edited by CTwireman (edited 03-30-2004).]


Peter
#36087 03/30/04 08:42 PM
Joined: Dec 2000
Posts: 4,294
Member
from Bomzin

"Here's a picture"


[Linked Image]

[This message has been edited by electure (edited 03-30-2004).]

#36088 03/30/04 10:04 PM
Joined: Dec 2003
Posts: 886
H
Member
This picture shows the insulation burned a short distance away from the backstab. Right next to the receptacle the insulation appears fine. Is that true? Also, what are those nicks in the hot and neutral? Were they always there or are they a result of your removing the wiring?

-Hal

#36089 03/30/04 10:05 PM
Joined: Feb 2002
Posts: 840
C
Member
Those look like Leviton #5248 "backwire only" receptacles. The only time I've ever seen those used was in Las Vegas and California. Must be a western thing.....

-Peter


Peter
#36090 03/30/04 10:41 PM
Joined: Mar 2004
Posts: 28
B
Bomzin Offline OP
Member
The nick on the nuetral is mostly because of wire seperation when I removed it from the box. The hot wire was found that way having melted back away from the wire. The hot wire did get warmer then the nuetral. Serious signs of heating were found on both wires.

No the wires did not burn right next to the receptacle or even into the jacket of the romex. Only on the exposed portions out of jacket.

I don't think this was breaker failure. It did trip before fire. It did pass the first trip test. I would say failed the second due to unknown reasons. There are alot of variables here.

After talking with the wife abscent the husband I would say when he turned it on for the second time the breaker held way to long right at it's limits.

The husband I do consider somewhat competant, he had managed to put in Arc faults for his bedrooms and had done varios switchs around the house including 3-way's. Like I stated before his work looked fine and no signs of damage in the areas he worked. I did check some of his stuff at his request and all was fine.

I've had a brain fart once or twice in my day and wired up a short. I average probably 3 service calls a day for many years now and have never seen this before, that I recall under these circumstances.

These people have lived in this home since it was new and I can rule out these folks loading up a circuit and throwing it on an oversize breaker.

Maybe this is just something that has been coming to a head due to other unknown circumstances. There are just to many variables and although I did look over everything carefully as we took it out. Because I do like to find the culprit so I can say, SEE HERE IT IS. It's just not to be the case this time.

I am happy to answer any more questions any of u may have on this, I think C-H had it right with an already impending high impedance path, probably made worse the first time it was energized.

Neil

#36091 03/30/04 10:44 PM
Joined: Mar 2004
Posts: 28
B
Bomzin Offline OP
Member
Oh and CTwireman wins the booty prize for naming that receptacle. You know they were budgeting when u see those in a home.

Neil

#36092 03/31/04 12:39 AM
Joined: Oct 2001
Posts: 597
E
Member
Thanks Neil & Scott for getting the picture up.

Neil, you certainly found an interesting one.

From the clues you've shared:
Quote
  • These people have lived in this home since it was new.
  • Like I stated before his work looked fine and no signs of damage in the areas he worked.
  • The wires did not burn right next to the receptacle or even into the jacket of the romex. Only on the exposed portions out of jacket.
  • There is no sign of damage to any of the devices. Only to the wiring.
The situation is truly puzzling.

The conductors inside the cable sheath being unburnt, and the devices being unburnt is a show stopper.

I wonder about the original construction crew. . .who they might have been; what they had to deal with in the way of weather. Are any of the floors finished wood that would have required a floor sander? (Around here, they're wild cards. I've seen'em hook cheesy alligator clips on unfused buses). But all of this would have burnt to the device. . .

It's almost as if, prior to devicing, too much heat was blown or radiated into the roughed in boxes, melting the exposed insulation. The ends that were eventually stripped and connected to the devices were back inside and somewhat protected from the heat. The original installer felt the damage would "get by" and left it.

Following on this idea, you may well have had two problems that you fixed. Beside the tripped breaker, you found and replaced legacy circuit damage left from the original construction crew.


Al Hildenbrand
#36093 03/31/04 09:19 AM
Joined: Mar 2004
Posts: 28
B
Bomzin Offline OP
Member
Was not cause by an external heat source. The switch box in the room had aother branch off of it running to a receptacle that was out of the loop. No damage on the power wire to that 1 Rec. But in the switch box the power wires hot and nuetral were melted that were in the loop .. Both under wire nuts

Also I think browning would be observed with that kind of heat on the jacket.

Neil

#36094 03/31/04 03:52 PM
Joined: Sep 2002
Posts: 1,498
Likes: 1
C
C-H Offline
Member
Alright, here is wild theory:

Let's assume the magnetic trip on the breaker failed. There is a short at a receptacle, which passes a lot of current for a second or two until the thermal element in the breaker trips or simply burns out. That's the "buzzz"

The wiring between the short and the breaker are heated very, very, rapidly by the current. As the insulation begĂ­ns to melt, the breaker steps in. In the jacketed part of the cable, the energy is conducted into the jacket and grounding wire thereby removing enough heat to prevent the conductor insulation from melting. Near the terminals, the heat is conducted into the metal of the receptacle which removes enough heat to prevent the melting of the insulation to continue.

The heat in the section of unjacketed wire that is far from the terminal has nowhere to go but through the insulation into the air and free convection and radiation at the outer surface of the insulation. This is much less efficient than conduction in copper or even in PVC.(*) End result is that the insulation melts.

* In fact, to calculate the temperature rise from a short circuit you usually assume that there is no heat transfer to the surroundings.

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