Melting Neutral Wire In Panel

WarnerConstInc.

So I was in my garage cleaning, my brother was working on a Bronco.

100A panel in garage, fed with #2 wire, all 20A breakers

One circut closest to the panel, 5 outlets, 12/2, 20A outlets.

Plugged into this was a set of work lights and a squirrel cage set on a
T-stat, kicks on every 15 minutes or so.

Work lights started cutting in and out, I walked by the panel and smelt something hot.

Opened panel and that circuts neutral wire's insulation was melting.

cut wire back re-installed and shut that light off. Had no more problems.


Is it safe to say his work light was having an issue?

Or issue with panel/wiring.

Nothing else in garage was affected/8 other circuts or so.

Winchester

Wow, talk about fire hazard!

My unprofessional guess is that it is a shared neutral with too much load on it. It's sharing load with another circuit somewhere that it shouldn't be (i.e. same phase?)...

My other unprofessional guess is the circuit was overloaded and the breaker wasn't tripping.

I hope that is the only spot the insulation was damaged.

__________________
Ryan

Leo G

Sounds like a loose neutral, extra resistance heated it up. Some sparky should be along soon enough to straighten us all out.

__________________
Sawdust Follows Me Everywhere

http://lrgwood.com
Custom Cabinets in Hartford County Connecticut

Winchester

*tap tap tap*

Man, the electrical section is dead compared to carpentry. They must all be over at electriciantalk talking bad about all of us on contractortalk. (That's what the painting guys do!)

__________________
Ryan

Magnettica

Does the neutral conductor share a pair of ungrounded conductors?

One red, maybe one black?

WarnerConstInc.

no it doesn't.

Magnettica

Some kind of buried splice in the wall maybe? Need to amprobe it and figure it out. Maybe it was just a loose connection at the bar.

mrmike

I agree here, as the work lights probably put it over the amperage of the wire and will start melting at a weak point, usually where the insulation is open.
I would check to see how much stuff is on this circuit with that neutral wire..
I would also check this breaker to determine if it is the right amperage for the wire. If it is, I would change it as it should have tripped. Don't ever think a breaker will always trip. They are sitting there for maybe years, & believe it or not, they will collect dust inside of it, as an example. We had many,many, breakers in the plant I worked in, that would not trip. A co-worker of mine actually had a 40 amp single pole breaker rigged to short out circuits in the field to try to trip the breaker he was looking for. THIS WAS DANGEROUS & is probably still doing it. I think he even burned up a few!! Anyhow, I just used this for an example to show that breakers do not always trip at their rated ampacity............

Celtic

That would be my conclusion as well.

I would also check/tighten the connections at each device to avoid any "complications" further down the road.

__________________

Celtic

A question:
IF the circuit was overloaded and not tripping, why did the hot conductor not suffer a similar fate as the neutral?



Some brands are notorious for not tripping...Federal Pacific [FPE] comes right to the top here.

__________________

WarnerConstInc.

No buried splices all wall cavity's are still open, the outlet that the light was plugged into was the first one in the circut from the panel about 3' away.

20A breakers, 12/2 wire, 20A outlets.

Does anyone read? All that was in my initial post here.

Celtic I dont know what kind of breakers they are, I know that the GE replaces the ones that are in the panel.
I had to replace the 100A main in the panel, it was arching out for some reason.

I still have a feeling that it was my brothers cheap ass work light he bought.

Celtic

Nope....poor connections at the neutral bus on that branch circuit.

The light ~ lemme guess: A 1500w quartz stand?

__________________

woodchuck2

Chances are regardless the cost of the lamp that the cord on it is smaller than the wire feeding the circuit. So IMO the lamp is not the problem. As stated above by others it is most likely a loose nuetral or a corrosion problem. No pics to go by so who knows other than you. Now that the nuetral is tight i would have the circuit tested for amp draw, wouldnt hurt to replace the breaker either. Whats a breaker cost, $5 at most. Cheap insurance in my book.

Winchester

Because rarely anything happens the way you expect it to

__________________
Ryan

Murray Ritchie

It has been suggested that the breaker should be changed out that it should have tripped. That may not be true in such cases as this.

It is true that current produces heat. More current, more heat. Drawing enough current, producing enough heat, to melt the insulation at the point of termination, could only be done if the neutral is shared. Otherwise the heat damage would be witnessed on the hot conductor coming off of the breaker too.

If the neutral was making poor connection to the bus, the resistance goes up, causing less current to flow. Meaning the heat is being generated by the continious making and breaking of the path of current to flow. When the circuit is under load, and is opened and closed, an acring occurs at the break and make point. This arcing will produce enough heat to burn a house down, let alone plastic insulation.

Verifying and knowing that the neutral is not shared, this is probable cause.

It hasn't been stated if the conductors were of copper or aluminum. But have seen in repeated cases as this in Alum. installations. Because of the properties of the al conductor to change physically over time.

WarnerConstInc.

hang on guys I will go pop the cover off the panel and snap a few pics.

WarnerConstInc.

heres the end of the wire in the first picture

Attached Thumbnails

     

WarnerConstInc.

last one shows outlet that light was pluged into next to panel

Now dont give me crap about how not neat and tidy the panel is inside.

Oh I lied, Siemens is what replaces the breakers that are in there.

I believe when my house was re-wired this was the old panel from in the basement.

Attached Thumbnails

 

Murray Ritchie

well its an old one for sure.....but rules out the aluminum, and would suggest poor connection at the neutral bus.

mdshunk

It heated up right at the bar... right at the point of high resistance. Resistance=heat. Loose connection! Don't over think this.