Charred grounded conductors

[Bain]

So I looked at a panel this afternoon, and the cables connected to the left terminal bar were charred and the insulation was melted in varying degrees. Thing is, though, all the wires connected to the right terminal bar were pristine.

I realize the cables in the photo are probably just loose, but it isn't logical that the installer got everything nice and tight in the right terminal bar, and then was totally careless when he got to the left bar.

Any other possible explanations?

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[Bill Kibbel]

Any other possible explanations?

No. In my experience, it's usually because of loose connections.

I'll bet that electrician forgets to tie one of his shoes on occasion. It's probably the left one.

[Richard Moore]

I would guess you just had the one loose connection. The subsequent arcing at that point was enough to heat up the bus bar locally and char and melt the other close-by wires. The damage seems to get less as you get further away from the worst of those near the bottom of your photo.

[Bain]

Ah . . . interesting. If that's the case, I'll bet it was the stranded 8-gauge wire. It had some yucko melted insulation.

[asihi]

Any other possible explanations?

No. In my experience, it's usually because of loose connections.

Loose connections will definitely create high resistance, but couldn't a shared neutral do this as well?

[msteger]

So I looked at a panel this afternoon, and the cables connected to the left terminal bar were charred and the insulation was melted in varying degrees. Thing is, though, all the wires connected to the right terminal bar were pristine.

I realize the cables in the photo are probably just loose, but it isn't logical that the installer got everything nice and tight in the right terminal bar, and then was totally careless when he got to the left bar.

Any other possible explanations?

Click to Enlarge

46.1 KB

It was probably a Friday afternoon install.

[Jim Katen]

Any other possible explanations?

No. In my experience, it's usually because of loose connections.

Loose connections will definitely create high resistance, but couldn't a shared neutral do this as well?

An improperly shared neutral will heat up along its entire length, not just at the connection point.

As a general rule, if you see heating at a connection point, it's because the connection is or was loose.

- Jim Katen, Oregon

[dnoel]

So I looked at a panel this afternoon, and the cables connected to the left terminal bar were charred and the insulation was melted in varying degrees. Thing is, though, all the wires connected to the right terminal bar were pristine.

I realize the cables in the photo are probably just loose, but it isn't logical that the installer got everything nice and tight in the right terminal bar, and then was totally careless when he got to the left bar.

Any other possible explanations?

Click to Enlarge

46.1 KB

Apprentice installer?

"This is how you do it..."

-Does it right a couple times

"Ok got it!"