Got a call from a customer I did an addition on their house 4 years ago. A new service was installed at that time to the home to accommodate the new circuits needed for the addition plus the old breakers were zinsco about 30 years old so we replace all the breakers and the service. He had a breaker flip during the night and reset it but lost a few plugs on the circuit. It is a 15 amp with 14/2 romax and about half way down the line a plug with power the next dead. After pulling out a few of the plugs of the circuit and seeing nothing wrong I ran the ohm meter across the ground and the neutral at the dead plug and had a closed circuit with the wires unhooked on the prior plug. So after a bit of time I cut open the wall to follow the wire in the wall. Just out of the box the wire had melted at a romax staple and burned about 4 inches up the stud, this staple had been on the wire for 30 years. The 14/2 wire in the other boxes had white jacketed romax but this one had a black jacket not that that had anything to do with it just more FYI. I pulled a new piece of 12/2 between the boxes to replace the burned wire. I am just not sure why it happened. I also replace the breaker that was a twin Murray 15 amp and checked the power draw on the stuff he had plugged in to that circuit just a couple TV sets and cable boxes drawing about 600 watts total. All I can come up with maybe the staple had thinned the wire at that point the wire had gotten hot then shorted and the breaker failed to trip ASAP but the wire has been in the wall for 30 years. The wires in all the boxes all looked good no color and also the wire at the breaker looked good but looking at the breaker on the side you can see a bit of waves in the plastic just a little bit. Not sure if maybe a lamp might have a short and when they went to bed it happened all I was told he got up in the middle of the night and the light would not come on and he went out and reset the breaker.
Burned Wire in Wall?
- Thread starter Jerry B
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mcclary's electrical
Senior Member
- Location
- VA
hotwire1955
Senior Member
- Location
- nj
putting an ohm meter across the ground and the neutrial ? they are connected together at the service.
mcclary's electrical
Senior Member
- Location
- VA
I read his statement to mean he had unhooked it from the feed side, therefore he knew there should be no continuity at that point. That's what led him to the staple
Jim W in Tampa
Senior Member
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- Tampa Florida
Being it was where the stable was i would assume it simply was too tight and bit into one of the 2 wires as your suggesting. What we will never know is before the wire was protected (or not protected) by the zinsco what kinds of overloads it might have had for 30 years on that wire. Assume you know about that brand and problems. Actually had you not installed the new panel there likely been nothing to go look at but asches. Why it took so long is hard to say.
One other but very unlikely thing to look at is if it has or had a bad neutral that the white was finding a partial path back thru the wood.
Customer was very lucky
This just proves that even after a panel change there is old wire that might been damaged because of them great zinsco welder breakers.
Welcome to the forum
One other but very unlikely thing to look at is if it has or had a bad neutral that the white was finding a partial path back thru the wood.
Customer was very lucky
This just proves that even after a panel change there is old wire that might been damaged because of them great zinsco welder breakers.
Welcome to the forum
- Location
- Illinois
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- retired electrician
Not really. These types of faults often do not draw enough current to open any standard overcurrent protective device. You can make a lot of heat from a problem like this while only drawing a few amps of power. The breaker will only see this as a load, not a fault. This issue happens with any brand of breaker or fuse.
A/A Fuel GTX
Senior Member
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- WI & AZ
- Occupation
- Electrician
I'm willing to bet this was a metallic staple. IMO, a plastic staple would greatly decrease the chances of this happening.
Jim W in Tampa
Senior Member
- Location
- Tampa Florida
What do you think would have happened with the old zinsco breaker when this problem did finally short out ?
Your idea is partly true but my opinion is the damage was started years ago with overloads that could not trip the breaker.
Jim W in Tampa
Senior Member
- Location
- Tampa Florida
In my 30 years of wiring i have never used anything but steel staples. Very rare that i damaged the wire put have seen green helpers do it till they get the skill level up.
Learning how to properly install anything electrical, including steel staples, would greatly decrease the chances of this happening.
I've never used plastic staples, and have never had a problem.
brian john
Senior Member
- Location
- Leesburg, VA
But had he meggered the circuits during the service change he MAY have noted a low reading on this circuit and suggested to the customer that further investigation was warranted.
mcclary's electrical
Senior Member
- Location
- VA
You can't be competitive in today's market and throw in a whole house meg for every service change. I did (3) service changes last week and did not use the megger once.
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Sorry this is not part of the NEC, maybe a local requirment but even at that, this requirment would be pushing the grandfather clause.
Jim W in Tampa
Senior Member
- Location
- Tampa Florida
might be good idea but its not the panel requiring them ,it is the NEW receptacles.
kwired
Electron manager
- Location
- NE Nebraska
Happens even easier with 277/480 volt.
By new I hope you mean the ones added on to the circuit.
- Location
- Simi Valley, CA
Boy, if they had one of those pesky new fangled arc-fault breakers, they might have noticed it earlier.
brian john
Senior Member
- Location
- Leesburg, VA
Everybody has to make their own decisions, there are ways to MAKE money from performing additional work as part of a educating your customers, placing you in a position above you competitors with their bottom line bids.
Just a thought.
mcclary's electrical
Senior Member
- Location
- VA
It's a really good thought. I'm just not sure if it could be justified on every service change. Everybody needs extra ways to drum up more work. How long would it take to meg 30 circuits?
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