Corroded wiring casing in basement - cause?

Question

I just had our annual furnace tune-up and the guy who performed the inspection gave us a B tag violation because the electrical supply wire to our gas furnace is corroded and copper wiring is exposed.  I am going to contact the company who installed it to look at fixing ASAP but the technician who found the issue said he has never seen it before and can't say what caused it.
The furnace is located in our basement near the foundation wall, and being an older house, there is some dampness/potential leaking happening (will have to wait for our first spring before we know the full extent) so my first guess would have been water damage, but could it have damaged the wiring this badly? And what is that white crusty stuff?
Furnace installed and all the electrical was redone in 2017 when previous owner flipped the house.
I am just wondering if anyone has seen something like this before and can confirm the cause, and if it's something I should be worried about reoccurring after the wire is replaced.

Ecnerwal · Answer

2017 - probably MC-Lite (aluminum armor) which you could verify by magnet, but the fact that the corrosion is primarily white leans heavily that way.
Given that much corrosion in 3 years, I'd suspect that it's getting something like acidic condensate from the furnace flue (or condensate drain) dripped or splashed on it, or there's water softener salt/brine getting onto it.
A third possibility would be if there was any concrete work associated with the "flipping" and concrete/cement got onto the cable and was not removed - concrete and aluminum are highly incompatible.
Aside from correcting whatever is contaminating the cable, or if you can't figure out what that is, this might be a place where liquidtight conduit and THWN would be a better bet than MC-Lite.

Corroded wiring casing in basement - cause?

One Answer

Add your own answers!

Ask a Question