![]() ![]() It has always dominated the skies of utility distribution. So with those application techniques mastered, aluminum is proving to be a winner for architectural electrical distribution. A new AA-8000 alloy was specially developed for interior electrical wire. The 1970s effort involved taking AA-1350 alloy "outdoor transmission line" wire and shrinking it down. It turns out the entire industry had been in the bottom quartile of the Dunning-Kruger curve, and many are still in denial. This was coupled with some trade-show testing that proved pro electricians couldn't set torques "by feel" any better than their spouses. However, for "the small stuff" (15-50A wires), no one bothered - they just cranked them down "gud-n-tite" with no particular standard for what that means.Īnd totally unrelated to aluminum, this was found to be a major cause of failure for copper connections, and of course there's no reason to think mistorqued aluminum connections were performing any better. This was a universal "best practice" that electricians did on large high-current terminals, and those have proven reliable in both metals. Torque terminals to spec with a torque wrench (NEC 110.14). Design standards were significantly revised (to CO-ALR), and those devices have terminals made of indium, a soft, conformant metal that mates well with aluminum. This caused frequent failure, and the postmortem revealed the rule I state above. UL hastily certified ordinary devices made of brass without adequate testing. ![]() This was done in response to a copper shortage, and the government ordered the certification agency (UL) to fast-track approval of switches, receptacles and splices. ![]() The exception that proves the rule is the 1970s experiment with small aluminum branch circuit wires in North America. When the aluminum lug envelops a copper wire, this thermal expansion works favorably. This works because aluminum has a different coefficient of expansion than copper. Panel neutral bars, large lugs, Alumiconn and Polaris style connectors all use this method. Generally, the simplest way to do this is to use a lug terminal which is itself made of aluminum. Use terminals designed and rated for aluminum wire (NEC 110.3). In practical application in house wiring, there are two "golden rules" called out on the first page of the Code book. The affordable process for refining aluminum requires staggering amounts of electricity, so by definition, aluminum enters a world that is already fully built-out in copper. It's 10 times the cost for the same ampacity!Ĭopper had to come first, because it exists primordially - you can find copper nuggets in nature, so it was one of the first worked metals in human history. Never mind copper being twice the weight for the same ampacity. And North American AC electrical wiring has achieved mastery of using it, including the unfortunate exception which proves the rule. ![]()
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