Recognizing vintage CO-AL receptacles and switches

[Stephen Tashiro]

It is written (on the internet) that in houses built in the 1970's with aluminum wiring, the wiring itself isn't the main source of problems. Instead, problems are due to people using receptacles and switches that weren't made for use with aluminum wires.

So, if I'm looking at such a house, how can I tell whether switches and receptacles of the 1970's vintage are made for use with aluminum wires? Would they have the same markings (like "CO-AL") on them as modern receptacles and sockets?

[Rollie Meyers]

It is written (on the internet) that in houses built in the 1970's with aluminum wiring, the wiring itself isn't the main source of problems. Instead, problems are due to people using receptacles and switches that weren't made for use with aluminum wires.

So, if I'm looking at such a house, how can I tell whether switches and receptacles of the 1970's vintage are made for use with aluminum wires? Would they have the same markings (like "CO-AL") on them as modern receptacles and sockets?


They should have CO/ALR stamped on the yoke, if you cannot see it when removing the plate it's just a standard device. If they are Decora® type, they are also not CO/ALR, in the early 1970's they went to a aluminum alloy conductor which is a major improvement over previous product, there is also copper clad aluminum, which can use standard devices, if buying a building wired with aluminum 15A & 20A branch circuits, might be worth asking for a price reduction to cover a rewire, but in a hot market might not fly.

Under 30 amperes devices listed for aluminum conductors are CO/ALR, 30A & larger are AL/CU, no marking is copper only.