ECN Forum Forums Code Related Discussion NEC & other Code issues Aluminum conductors

Steve, while it did wander a bit, the topic didn't get too far off track.

The 'simple' answer is: Yes, the NEC allows aluminum wire to be used for feeders and branch circuits. This 'simple" answer, though, is misleading.

It is misleading in that aluminum wire is not made in sizes small enough for the most common of branch circuits, the 15 and 20 amp 'convenience' receptacle and lighting circuits.

It is also misleading in that the great majority of breakers, lugs, and devices are not approved for use with aluminum wire. This puts you in the position of having run wire that you can't connect to anything.

There is also a bias in the replies - a bias founded upon a half century of experience with aluminum wires - that wants to discourage you from using aluminum wire at all, especially in branch circuits.

Also, if you have a specific application - say, a swimming pool - you may find specific NEC rules against the use of aluminum wires.

Pardon??
I thought they were tinned copper.
Are you using cheap, imported, sub-standard lugs, Greg?

Scratch one of those lugs and get back to me.
Cu/Al rated lugs are usually aluminum here

Mike, none of the above are true.

One of the major lug manufacturers, Ilsco, is based in Ohio. The lugs are copper free aluminum, and suitable for use with either copper or aluminum conductors.

Virtually ALL of the panelboard manufacturers here use aluminum for their neutral bars.

Here's a link: http://www.ilsco.com/productcategor...amp;akjdjfv=eutBkn2tkwr6Bt9t9WBHZA%3d%3d

We might be over-simplyfying the issue here.

The first one is composition; that is, most all metals used are some form of alloy. If you really got technical, I expect you would find that the aluminum in beer cans isn't quite exactly the same as the aluminum in bicycle frames. This is relevant, in that there WAS a change in the alloy used for aluminum wire around 1978.

The second relates to the connection method. Even in 'the bad old days,' I'm not aware of aluminum connections under lugs being the issue. Rather, I seem to recall the problems arising in connections in the following order:
- 'back stabbed 'spring loaded' types of devices;
- Conventional 'wrap it around the screw' connections,
- inside wire nuts (wire breaks)

Let's face it; in a conventional lug, that wire isn't going anywhere, no matter how it wants to expand and contract. The picture changes when the wire can 'squeeze out' the side of a clamp, or away from a screw head.

Naturally, out in the field we're not going to be performing a complete engineering study for every wire connection. Instead, we tend to 'keep it simple;' and one of the tried & true rules is 'stay away from aluminum wire!'

We had an Alcan rep at an IAEI meeting explaining this aluminum deal to us. He said the device problem was really the steel vs brass screw problem. The expansion rate of steel is different than aluminum and that was the root of the problem. CO/ALr devices use a screw that is a brass alloy matching the expansion of the new AA-8000 aluminum alloy.
He said another problem was the old alloy was a lot easier to break than the new stuff and passed around samples of both for us to destroy.
The older aluminum was 1350(?) alloy that is used for large transmission lines and in those sizes using that kind of termination methods, was not a problem.

They were pitching the new MC cable with the fat, bare aluminum ground, the new connector for that and some other products.
That was when copper Romex was getting "golden" prices.
He stopped just short of saying we might start seeing 12 gauge aluminum wire again.