How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
site-built, mobile/manfuactured and modular homes
When did they stop using aluminum wiring?
Friday, February 7, 2020
Aluminum wiring has never stopped being used. Only a particular type of smaller-gauge single-strand aluminum is no longer available for residential wiring. It was substituted for copper from the mid-1960s to the mid-1970s because the price of copper skyrocketed during that period.
Solid aluminum wire turned out to have several problems that caused a lot of house fires. It has a high coefficient of expansion/contraction compared to copper, and the movement loosened of wire connections. Corrosion was also a problem, and aluminum is softer than copper and easily nicked. While it is a good electrical conductor, if not quite as good as copper, the surface corrodes to aluminum oxide, which is an insulator. Although that type of wire is no longer manufactured—and special switches, receptacles, and breakers rated for use with it were approved as a retrofit safety fix—many insurance companies will not insure a house with this wiring unless inspected and approved by a licensed electrician.
Many new homes today have multi-strand large-gauge aluminum wiring as service cables to the main panel and from the panel to major appliances, such as an electric range or furnace, and it is quite acceptable. The exposed wire at connections is usually coated with the required gray or black anti-oxidant paste, as shown below.
And here’s an example of aluminum wiring at lugs with the anti-oxidant paste missing.
Also, see our blog post I heard that aluminum wiring is bad. How do you check for aluminum wiring?
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