u/SAMEO416

Visitor to our cabin last night.

House renovation underway, and the demo crew cut some receptacle NMD that used to feed two receptacles in opposite sides of a pony wall.

I replaced these receptacles 15 years back due to retention force issues. At that time I noted the ground wire was blackened. I assumed there had been some kind of fault with the previous owners.

Now that I can see the wiring, have to say I’ve never encountered this before.

Both receptacles are fed from the same 15A breaker.

There are two NMD runs, one to each receptacle.

This is the weird part - then the two outlets are daisy chained to each other.

I’d expect one or the other, not both.

There’s heat damage to both NMD over the ground wire. One junction box has heat marks over the hot screws, and the hot screws look partly melted.

This is a problem which dates to original construction in 1992 (Canada). It’s apparent there’s been continuous heating but not enough to trip the breaker. I did measure current on the house ground a few years back but it wasn’t unusual.

What I believe has happened is the dual feeds created a net current flow because of the different length of NMD, having slight differences voltage drops.

Anyway, never encountered this in 10 years of residential fire investigations. Any ideas welcome.

Cabin near Athabasca, Alberta.