Sketchy ground situation

DavidD

Member
Location
Canada
Occupation
Retail
Hello,

Wondering if anyone has seen something like this before or what the cause might be (and suggestions).

I had to open up an outlet the other day and found the ground looked like someone had used insulated cable. Upon taking it apart further, it looks like there is an excessive amount of grease/residue on the ground wire - making them look essentially black. On this the box grounding locations are also nearly completely black. After a quick wipe there was some blackening on the end still (perhaps real oxidization) - I lightly sanded it off before reinstalling this one. At this point I did not mess around with the box grounds.

I checked all our switches and outlets in the house, and a number of them exhibit this with the grounding wire to various degrees (some appear like whatever is on it is 'fuzzy' almost like someone put grease on it and then pure black dust) . Some however are perfectly normal with not a hint of a problem. Some within the same switch box 1 side will be fine, the other will show some gunk on it.

I have not fully inspected hot/neutral but on this one they appeared to be clean (from what I could see).

(before any cleanup)
(after a quick wipe, and showing box grounds)

This is a ~20 year old house in Canada. This is a cheap townhouse condo build so I would expect the bare minimum and cheapest materials have been used.

Could this be residue left behind from the manufacturing of the cable to begin with? And over the years seemingly just the ground has managed to collect gunk on it? I only suggest this as a possibility because I stripped some spare cable (not original to this house) I had laying around and the white (nylon) where the ground wire would be had some black stuff in there and the ground wire felt a little greasy.

Thanks so much.
 

Coppersmith

Senior Member
Location
Tampa, FL, USA
Occupation
Electrical Contractor
Looks like Chinese drywall corrosion. Hydrogen sulfide outgassing from drywall. If it is, the entire exposed copper portion of the wire will be black.
 

DavidD

Member
Location
Canada
Occupation
Retail
Does that really manifest itself partly in a greasy substance? I also have some where within ~3 feet one is good and one isn't. From what I've been reading most of the so called Chinese drywall issues affect basically everything in the house due to the amount of off gassing?
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
There is also the possibility of a liquid coming from the plasticizer in the cable insulation. This is not believed to be a direct hazard and may be a coincidence of both cheap NM and cheap drywall. The sulfide corrosion is more of a problem and may be associated with unhealthy air quality lasting for years.
I would recommend testing to the occupant.

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