Never seen this before

Did a house yesterday, and the electrical panel is outside at the meter. It is a Siemens panel. First, the copper wire is black where it’s exposed. That got my attention, but then I was really concerned when I saw the conductors had been cut open.
I can’t see a reason for this to be like this, but called it out to the buyer. Any comments?

That could be several things all related to some airborne chemicals, most likely sulfur in some form. It looks a lot like what chinese drywall does to copper, but I’m not sure how the fumes would get into the panel.

Were there any open sewer issues?
Is it a known meth lab?
Is there chinese drywall inside?

Knowing a little more about the house will help. That electrician was sure sloppy with his knife! :wink:

For sure.

Close to swimming pool/chemicals?

What do the wires look like on the inside of the home and the receptacles and switches? Did you check the a/c coils? What year was the home built? Does the home have copper water supply lines and if so, did you notice what their condition was?


When exposed copper turns black it can indicate voltage leakage. Judging by the cuts in the wires, I would say when those wires were stripped, someone was indeed sloppy with the knife as was already suggested. If you are finding other copper components in the house that are darkened or black, such as copper pipes, it would serve to further validate the voltage leakage theory.

If the cut were only in the nylon jacket then the conductor is fine. Since the black conductor has copper showing in the photo then it must be repaired.

Could you please explain the voltage leakage theory? Where is it leaking to and why would this cause a color change?

FWIW I have seen the color change from just being out in the rain during rough in.

To answer - I immediately checked the A/C coils and several receptacles as Chinese drywall popped into my mind. But it was all bright and shiny. No other metal looked corroded at all. I just thought this was unusual to see it in an exterior panel.
The house was built in 1999, and there are no plumbing fixtures nearby. Anyway, I showed the box to the buyer and explained why he needs to get this fixed soon.

Could the electrical components themselves be off gassing in some way to produce this?

I ask only because where would any corrosive airborne agents come from, let alone get into the panel?

Storage box for pool chemicals nearby?