Discolored bare grounding conductors in panel

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tonype

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No obvious sources of moisture or evidence of overheating; however, bare conductors are "dark" - see photo. Wiring is not that old - 80's and 90's vintage. This is a sewer odor in the basement - could there be "stuff" in the sewer gases that would cause this??
 

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Most of the work I do is ag/dairy work. Most, if not all the panels around the farm have an almost black #4 bare running down to the rods. However, if you pull the ground wire out of the lug it is still shiny where the set screw is making contact.
 
Exposed bare copper will eventually darken from oxidization, no special corrosion necessary and the oxide layer decently conductive once a volt or more is applied or you tighten it down in a terminal or wire nut. But for a new termination it is a good idea to shine it up first, especially for a crimp.
 
In terms of the CU, it is fine as long as it is terminated properly. In terms of the OTHER issues in your images...well those can be fixed:angel:
 
tonype said:
No obvious sources of moisture or evidence of overheating; however, bare conductors are "dark" - see photo. Wiring is not that old - 80's and 90's vintage. This is a sewer odor in the basement - could there be "stuff" in the sewer gases that would cause this??
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Yes...H2S can cause this. That is very minor compared to what you would see in a sewage treatment plant.
 
tonype said:
This is a sewer odor in the basement - could there be "stuff" in the sewer gases that would cause this??
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Sewer gases may include hydrogen sulfide, which will corrode copper and turn it black. A sewer odor is a good clue as to the cause. I'd recommend that the homeowner contact a plumber. Sewer gas isn't too healthy to breathe. And besides, it smells nasty! :sick:



SceneryDriver
 
Chinese drywall?

Chinese drywall?

Looks like what happens to wiring when Chinese drywall is present.
Is the discoloring only at the panels?
You might also check a few devices inside the home and or the AC air handler for similar signs.
 
I had a pump station with a small hypochlorite dosing system. it was outgassing chlorine gas, turned the bare copper a bright shrek green. Later the dosing system was moved to a separate building - still causes corrosion there but no electrical gear.
 
cpinetree said:
Looks like what happens to wiring when Chinese drywall is present.
Is the discoloring only at the panels?
You might also check a few devices inside the home and or the AC air handler for similar signs.
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interesting !
I would never have thought of that.
Have you experienced that in the field ?
 
mopowr steve said:
Agree, sulfur could be the culprit.
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Many people assume that what they smell in sewer odor is methane. That can't be, as methane is odorless.

The smelly constituents are hydrogen sulfide, ammonia and Sulfur dioxide.

That makes sulfur sound guilty of the patina on the copper. I think the corroded neutral was caused by, or at least the cause was aggravated by something else, though.
 
K8MHZ said:
Many people assume that what they smell in sewer odor is methane. That can't be, as methane is odorless.

The smelly constituents are hydrogen sulfide, ammonia and Sulfur dioxide.

That makes sulfur sound guilty of the patina on the copper. I think the corroded neutral was caused by, or at least the cause was aggravated by something else, though.
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Unlike hydrogen sulfide, sulfur dioxide is acutely toxic. My high school Chem teacher, when asked what sulfur dioxide smells like, answered:
"It smells like your chest has been run over by a truck."
 
tonype said:
No obvious sources of moisture or evidence of overheating; however, bare conductors are "dark" - see photo. Wiring is not that old - 80's and 90's vintage. This is a sewer odor in the basement - could there be "stuff" in the sewer gases that would cause this??
Click to expand...

Is there AL service conductors without any nolox on it? AL will corrode/oxide in the presence of hydrogen sulfide just as easily as CU. Check this out for a comparison-

http://www.caslab.com/News/identify-problem-chinese-drywall.html
 
The only environmental conditions that I've ever seen corrode aluminum are water seepage from concrete and contact with very alkaline soil. I'd be interested in reading about gas corrosion, because I've run never into it.

This is good paper on the basics of corrosion for the metals we use in the electrical world.
 
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