Burned Wire in Wall?

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Jerry B

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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.
 

mcclary's electrical

Senior Member
Location
VA
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.


It sounds like the staple was overdriven.
 

Jim W in Tampa

Senior Member
Location
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
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
...
This just proves that even after a panel change there is old wire that might been damaged because of them great zinsco welder breakers. ...
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.
 

Jim W in Tampa

Senior Member
Location
Tampa Florida
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.
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.
 

480sparky

Senior Member
Location
Iowegia
I'm willing to bet this was a metallic staple. IMO, a plastic staple would greatly decrease the chances of this happening.
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
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.
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.
 

WinZip

Senior Member
Is it in 2008 that if you change a service you have to use AFCI breakers in those areas , seems to me I heard this not long ago.
 

kwired

Electron manager
Location
NE Nebraska
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.
Happens even easier with 277/480 volt.
 

brian john

Senior Member
Location
Leesburg, 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.
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
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.
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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