Wire markings - aluminum?

petepie1February 9, 2010


I have a house built in 1967 with some aluminum wiring. I'm trying to figure out if it is all aluminum branch wiring. Some of the wires are marked "Kaiser Aluminum KA Flex", that's the obvious one. There are two other types marked:

1. "Essex 14-2G Non Metallic Sheathed cable type NM-B 600v"

2. "Triangle Thermo-Triex Type NM with ground 12/2"

Are these copper wiring? I'm thinking a previous owner may have rewired some of the old aluminum circuits.

Thanks for the help.

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I can't tell from those marking what type it is.
The NM-B was installed after 1985, because that is when that rating started being used. The -B indicates 90ºC wire instead of 60ºC wire.

    Bookmark   February 9, 2010 at 10:56AM
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I have some Triangle 12/2 in my house (1978) and I'm pretty sure it's copper. I can double-check tonight. (It damn well better be copper ;)

    Bookmark   February 9, 2010 at 12:26PM
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Pretty sure #14 was never allowed for aluminum so it ought to be copper.

    Bookmark   February 9, 2010 at 12:37PM
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I have #14 copper wire on one circuit in my house.

    Bookmark   February 10, 2010 at 10:16AM
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Sorry that should have said
I have #14 aluminum wire on one circuit in my house. It was installed in the mid 70s.

    Bookmark   February 10, 2010 at 10:17AM
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I checked the Triangle cable in my house last night. It's copper. (Or at least the ground wire is...the receptacle is backstabbed.)

    Bookmark   February 10, 2010 at 10:20AM
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Thanks for all the responses. I poked around some more, and it looks like only the Kaiser Aluminum marked wire is aluminum -- the other two are copper. Was glad to see that at least some of my circuits are copper!

    Bookmark   February 10, 2010 at 3:43PM
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From what I understand, aluminum wire can be safe if it's spliced properly with copper. Am I right?

    Bookmark   February 10, 2010 at 4:19PM
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The cable marking should have 'Al' or 'Cu' as part of the marking.
It is often a rather long string of characters so reading it all can be a PITA.

Small mirrors come in handy.
The 'mechanics' articulated ones make it a little easier.

    Bookmark   February 11, 2010 at 8:51AM
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Globe199, your question is partly accurate. There are receptacles and switches made specifically for aluminum wire but they are expensive. Perhaps an aluminum receptacle is $5.00, where a standard receptacle is a $1.00 or less. However, to pigtail copper on aluminum, requires special wirenuts containing an antioxident to prevent reaction of the two different metals. It is somewhat similar to diaelectric unions used in plumbing. I have not seen aluminum wire lighter than 12ga. It is common to pigtail 14-2 copper to 12ga aluminum. In my opinion, aluminum wiring is safe if it is properly handled and connected.

    Bookmark   February 12, 2010 at 9:33AM
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Ron Natalie

Purple wirenuts (TM) are one listed way. There are some experts who are not overly satisfied with that solution. There's also the specialized CUPALUM crimping technology or little terminals where the aluminum and copper wires are under different screws.

Tex is right, any place that was ever remotely compliant with the NEC never had 14gauge aluminum. A 15A circuit needs 12 guage Al. 12G alum is only good for 15A, so 14g copper is allowable.

    Bookmark   February 12, 2010 at 11:04AM
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SAFE and DANGEROUS are very misleading words. Everybody has a diferent definition in there mind. Copper is safer than aluminum wire even with all the special fixtures and "fixes". Aluminum with one of the "fixes" is safer than aluminum without the "fixes".
You decide just how much risk you are willing to take. I rewired my house.

    Bookmark   February 13, 2010 at 4:30PM
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We're slowly trying to rewire as we work on rooms and expose the wiring, or at least get the aluminum out of the more heavily used circuits.

    Bookmark   February 15, 2010 at 11:14PM
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Re: Danger of Aluminum

Copper is better than aluminum for 2 main reasons.

First, aluminum expands about 10 times more than copper when heated. It is still a tiny amount, but over years of use, it could cause loose connections.

Second, aluminum joints tend to build up oxidized layers even when mechanically fastened with normal wire nuts, screws etc. That causes resistance and heat. If it gets bad enough, the temps can get hot enough to melt plastic and cause fires.

Of course, the vast majority of electrical fires are because a homeowner does something stupid. The actual branch wiring of a house rarely fails catastrophically. Aluminum might be 50 times more dangerous than copper, but 50 times a tiny, tiny percentage is still a pretty small percentage.

    Bookmark   February 16, 2010 at 9:29AM
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