Aluminum wasn't used much for branch circuits until about 1965 when
copper prices went up. There were enough problems that about 1971 UL
removed the listing for wire, switches, receptacles, wire nuts, ... then
put out new standards. The new switches/receptacles are marked CO/ALR.
The vast majority of installed wire is the "old technology" stuff. Use
died out about 1973.
Because of the problems the CPSC started an investigation, and tests
were done which included thousands of connections in various
combinations. The engineer that was behind the testing has a paper on
aluminum connections at:
One of the major problems in making connections, with both the new and
old wire, is thin oxide which is an insulator and rapidly forms on
'clean' aluminum. Many of the connection techniques involve both
antioxide paste and abrading the wire to remove the oxide.
For splices he recommends Alumicon connectors:
they are UL listed for aluminum (also in gfretwell's post).
The only other UL listed connector I know of is Ideal #65 wire nuts. The
author specifically is not fond of them. One reason, if I remember
right, is the metal the spring is made of. Details are in the paper.
Before Alumicon, the author had an older paper:
which describes using other wire nuts and why he likes them better.
Since the other wire nuts are not listed for aluminum an inspector may
have problems. On the other hand, the recommendations are based on
comparative research using the wire that is actually out in the field.
The problems were only with 15 and 20A branch circuits. Aluminum is
often used in larger sizes like service wires. The connectors bite into
the aluminum, which as gfretwell notes is similar to what happens with
But, of course. I'd have thought that the ox is the creature
doing the goring. The victim, naturally would be someone
like a Mexican torreador, or the american tax payer, or
someone relatively innocent.
In any case, it's good for aluminum wire, and many other
applications. I've been known to put a shot of Ox Gored on
copper connections, when exposed to the weather. I do work
on outdoor equipment. It's some what protected, but not
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