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Broken wire inside electrical box
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Posted by bill_g_web (My Page) on Tue, Jun 30, 09 at 18:03
| The broken wire was 12 AWG Cu pigtail to a split receptacle on a 3-way switch and the first indication of trouble was a tripped breaker which turning on one of the switches.
I'm wondering what the cause of this was and have two ideas:
1. An insulation nick lead to shorting, which in turn broke the wire by burning.
2. I bent the wire repeatedly during the receptacle installation, 4 years ago and weakened it to the point of a near break.
I'm guessing # 1, but maybe people have other ideas. (I'm humbled/frightened by this short circuit situation.)
Thanks,
Bill |
Follow-Up Postings:
RE: Broken wire inside electrical box
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| Insulation nicks (unless the wire was touching some other conductive surface) wouldn't cause a failure. However, if the conductor itself was nicked, it would now have a higher resistance due to the decreased cross section. It could quite well locally heat up at that point and further degrade. Chances are it was that and movement through thermal cycling (heating up and cooling down). Once it gets to the point of arcing it can get really really hot. Normal wiring protection via overcurrent breakers sized to the wire assumes that the wire is intact and won't heat up with currents less than the breaker. All that goes out the window with a poor connection (bad contact, smaller than rated wiring due to nicks, broken strands) and arcing. It will get hot in a hurry. THis was a major motivation for the AFCI changes. |
RE: Broken wire inside electrical box
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| Thank you, ronnatalie, for the reply. I must have nicked the wire. After this scare, ACFIs look affordable. |
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