How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
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Do any pre-1960 houses have aluminum wiring?
Thursday, August 30, 2018
No, we have never seen any aluminum wire in pre-1960 homes. Although it has been used since the early twentieth century by utility companies for electrical transmission in high-voltage power grids, copper wire has long been the standard for residential wiring. Solid aluminum (not multiple strand) wire was used only briefly for general home wiring, from 1965 to the mid-1970s, as a copper alternative during a period when copper prices skyrocketed.
An example is shown above. But the large number of house fires, caused by connections of single-strand wires working loose at wire terminal connections, ended the the era of single-strand aluminum home wiring.
Although single-strand aluminum wiring is gone, multi-strand aluminum wire is still an approved residential wiring and we see it used regularly for the main service wires from the outside weatherhead to the panel and also at breakers for major appliances. Because it is required to be coated with anti-oxidant paste at the wire connections where the metal is exposed to the air, sometimes the only way we know that it’s aluminum wire is the presence of the black or gray anti-oxidant goo, like in the photo below.
If you peek inside the electric panel in a pre-1960 home—which, by the way, we do not recommend unless you are looking over the shoulder of a home inspector or professional electrician—it may appear that some of the larger, multi-strand wires are aluminum, based on the silver color of the wire strands, like the two wires connected to the lugs in the photo below.
But these wires are actually tin-coated copper, which was used up until the mid-1950s or so. If the insulation is rubber with an embedded cloth sheathing, the wires are definitely tinned copper and, if you look closely at the exposed metal at the connection to the lug or circuit breaker, you can usually see little gleaming flecks of copper color where the wire has been nicked when the insulation was stripped back.
Also, see our blog post I heard that aluminum wiring is bad. How do you check for aluminum wiring?
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