Dark grounds

Originally Posted By: rdawes
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pic 1 ]


[ Image: pic 2 ]


And in this one the ground bus is to the left under the black and red hot conductors.
[ Image: pic 3 ]

The coating can be scraped off which I did on the left side of the ground from the service entrance seen in pic 1. Why is it there? What is it's purpose?

Thanks,
Ron


Originally Posted By: Greg Fretwell
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If everything else wasn’t so clean looking I would say it was some sulfur rich air contaminant. That is exactly what the copper looks like in my aireator tank (that takes sulfur out of well water)


Originally Posted By: pdickerson
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http://www.nachi.org/bbsystem/usrimages/P/P1130377.JPG ]


I would sure like to know what causes this. this is a photo of a sub panel located about 10 feet from a hot tub. The grounds have that same black look. I wondered if it might have been caused by the chlorine in the hot tub.


Originally Posted By: rdawes
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My first thought was some type of corrosion but look at the hots where they enter the breakers. Those are clean and normal. If airbore contaminants were to blame, then they should have been affected too.


Originally Posted By: Greg Fretwell
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Actually there are only a few that are not affected. I would suspect they may have been added later. Look at the main and the breakers near the top.


Originally Posted By: rdawes
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Pic 4 ]


Originally Posted By: Greg Fretwell
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There is another possibility. The cable might have been in a flood prior to installation. The paper would have wicked water along a significant length of the cable, discoloring the bare neutral but leaving the insulated wire somewhat unaffected, except near the ends. Once it dried out that would be the only outward indication.


I only say this because the issue came up over at Bob's house.


Originally Posted By: Jay Moge
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this is wierd. if you look closely at the neutral bar in pic. 4 you can actualy see the different stages of what ever is causing this. some are fine and some are slightly black and some are more so and all dagrees inbetween. i’d love to know. icon_cool.gif


Originally Posted By: pdickerson
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It looks like the 12 ga wires are OK, and the 14 ga wires are black. That might lend some weight to Greg’s “wet roll of wire” theory. Or maybe there was some other property of the 14 ga roll of wire that predisposed it to oxidation. I would like to know as well.


Originally Posted By: cbuell
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I really liked the wet roll of wire theory too----but what about the larger bare GEC. Can you tell us what the general vacinity of the panel looked like?


Originally Posted By: rdawes
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Perfectly fine and normal. Dry, no chemicals, the ouside of the panel and the wall were like new.


Originally Posted By: Blaine Wiley
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I see this frequently on exterior service panels, or garage located service panels. One of the local electricians here says it’s common, doesn’t cause any issues, and comes either from the salt air, or the sulphur air from our irrigation wells.