Aluminum wire to subpanel, arching at breaker


Old 03-06-10, 10:14 AM
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Aluminum wire to subpanel, arching at breaker

The house has a main 200-amp main panel and a 100 amp subpanel. There are aluminum lines to this subpanel and the connection at the 100 amp breaker (in the main panel) was arching under heavy loads causing the lights to dim. I could wiggle the wire and see arching.

I am replacing the 100 amp breaker, and cutting back the old bare aluminum to get clean wire since the original connection was blackened and smelled a bit.

I've heard aluminum must be treated different than copper.

Do I need to use that gel/putty on this breaker connection?
Do I just treat it like copper wire and strip it back about 3/4 inch, insert and snug the terminal screws?

Thanks for any help.
Old 03-06-10, 10:55 AM
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Use an anti-oxidant on the cables and use a torque driver to tighten the circuit breaker screws to the manufacturers recommended value.
Old 03-09-10, 11:24 AM
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Aluminum wire is permitted (and often used) on subpanel feeds and other larger feeders. As Ray said, use a wire brush to polish the wire then coat it with a no-Ox grease meant for aluminum wire.

It sounds like the lugs were not tightened correctly on the original installation and started loosening up over time.

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