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noalox compound
any electric experts help me understand what anti oxidantjoint compound is used for. i am getting the stuff for my garage, having new service put in. i am buying the items and never seen or heard of this.
aluminum service to panel box, everything else is copper.
thanks
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noalox compound
Antioxidant is just that - it coats the metal to keep oxygen away. Oxygen causes surface corrosion (oxidation). Even a tiny bit of oxidation will cause resistance at connections to increase. Increased resistance causes increased heat. Increased heat causes thermal expansion. Aluminum expands and contracts more with temperature than does copper, thus loosening the connection with each thermal cycle. Remember years ago when there were a bunch of house fires blamed on aluminum wiring? Reports are it was caused exactly by this problem.
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noalox compound
Exactly. For decades high-tension wiring has been mostly aluminum, which conducts almost as well as copper. When alum wiring was first offered for housing, it was seen as lighter, cheaper, and more flexible than copper, and the problem of it interacting with copper when the two were joined, for instance in junction boxes, didn't appear for some years after installation. That chemical is designed to make the alum as inert as the copper. (In my jurisdiction it's now illegal to use the two together.)
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noalox compound
Aluminum and copper are still routinely used together, the device just has to be UL listed for Al/Cu usage. For example buss bars in panels and contacts for breakers are almost all aluminum. Breakers still accept copper wires (in Residential wiring this usually = romex) at the screw in contact point where you have an aluminum screw / receptacle and a copper wire. The antioxidant compound is most needed at the point where the service cable neutral enters the panel and is attached via screw lugs to the neutral bus. Often water enters the cable (SEU type) outside and travels down the cable beneath the first insulation layer (plastic compound) along the outermost aluminum sheathing (neutral). This water then comes in direct contact with the aluminum bus bar in the panel before it has opportunity to evaporate.
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