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Mixing AL and CU at main disconnect


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Both legs look like copper to me. Am I not seeing it correctly?

Copper SEC into aluminum lugs. In that case, would paste make any difference?

My guess is they are both copper. The one is corroded/oxidized.

I am willing to bet that they are not aluminum lugs.

My reply was a general reply that one can use aluminum and / or aluminum as a feed/ feeder

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As long as the lugs are listed for use with either aluminum or copper, it's not a problem.

Then how do you explain the corrosion on the lugs?

Corrosion can be caused by all sorts of things other than incompatible metals. We all see it all the time. It could be that there were originally two aluminum wires, and one of them corroded and was replaced by copper.

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  • 2 weeks later...

The conductors appear to be the same size. This would be an issue if one is AL. (lower ampacity rating)

Your eye might be better than mine, but there might also be some optical illusion because of the different colors. When I hold up a caliper to my screen, the two conductors seem to be nearly identical in diameter. Since compact stranded aluminum wire is typically smaller in diameter than copper wire of the same gauge, I suspect that the aluminum is at least one gauge larger than the copper. It's really hard to tell.

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Foundation crack at the service entry ell; finished basement covered it up. Sucker probably leaked for a decade, then someone finally patched it with epoxy injection.

The equipment was shot. That white powder thing is wild; the disconnect had pretty much gone to borax; I don't know how it was conducting electricity.

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What about this? The whole mess was turning into white powder.

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When I see that I look for water stains on the service entrance conductors entering the top of the panel. Water often enters the meter socket and flows into the panel.

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Aluminum wires don't like to get wet. I was working in my shop one day when I lost power on one leg of the 240-volt feeder. The pictures show what I found when I dug it up.

Maybe because its anodic index is so high. Remember galvanic action between dissimilar metals? 2000 series wrought aluminum is -0.75 whereas copper is only -0.35.

Marc

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Aluminum wires don't like to get wet. I was working in my shop one day when I lost power on one leg of the 240-volt feeder. The pictures show what I found when I dug it up.

Maybe because its anodic index is so high. Remember galvanic action between dissimilar metals? 2000 series wrought aluminum is -0.75 whereas copper is only -0.35.

Marc

That could well be it, but I don't know what the cathode would be in that trench. There aren't any copper deposits here.

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