Are aluminum conductors allowed for all feeders and branch circuits? Code sections? If someone can guide me to a previous thread on this, that would work too. Thanks.

Technically, as the code is written, there's no reason not to use aluminum for nearly everything. True, there are a few exceptions, such as certain grounding conductors where the NEC specifies theat aluminum shall NOT be used, but those are the exceptions.

Indeed, the aluminum wire makes will tell you that aluminum is every bit as reliable as copper.

Yea, right. The wire makers leave out a few details:

They neglect to mention the change they made in the alloy used in the late 70's, to address issues that - they still claim - were caused by poor installation.

They also neglect to point out that they don't make the stuff smaller than #6 anymore. So, while there's no rule against using all aluminum to wire a house, lots of luck finding that #12 Romex in aluminum.

The same paradox exists as to the use of anti-oxidant compounds. The wire makers say there is no more, or less, reason to coat aluminum than there is copper. The NECA standard seems to assume that you will use it when working with aluminum, but doesn't specifically tell you to use it. The NEC is silent on the issue.

This is -yet again - where 'trade practice' varies from what the rule books say. Personally, I'll stick with tradition.

Check with the local AHJ as to the minimum sizes allowed.
Most of them have no problems with Aluminum feeders but do have a cutoff size that they won't allow to be anything but Copper.
Around here, it's usually 10AWG and smaller, but it pays to check it out.

So where/how does 110.5 apply?

PLEASE, please, please don't tie copper and alu together under a wire nut, even if "they" say that the nut is made specifically for that purpose.

Who are the "they" you're talking about? Do you know something that UL doesn't or have you fallen for the scare tactics on one of the web pages that I swear is funded by the makers of the copalum splices?

The only drawback I can see to the wirenut that is listed for copper to aluminum is its large size, hard to jam back in those undersized boxes they use in the old mobile homes.

Personally Tom,
There is absolutely no way that I would EVER put an aluminium wire and a copper wire in the same termination and call it "safe".

Sure the copper wire might be fine, but screwing a wirenut over an aluminium wire, is just asking for trouble.

These sorts of connections depend on friction only, not the sort of thing you want to subject aluminium to, as it has the habit of "flowing" under mechanical stress.

Especially when these connections are also carrying current, which will heat any sub-standard connection up, possibly to the melting point of the metal.

Bi-metallic lugs and splices are there to be used for a reason, otherwise, we wouldn't have them.

UL= Underwriters Laboratories. The clue is in the name. If a product is approved, then it must have passed their tests, surely?

Not sure if this relates to the OP's question or not, but the thing I find a little unnerving about the Ideal purple wirenuts, is that the manufacturer has multiple warnings on the package that they are designed only for connecting aluminum-to-aluminum conductors with another copper conductor present, but not for straight aluminum to aluminum only.
Not sure about the T&B Marette ACS wirenut though, but according to the T&B product literature, they are not even UL Listed, so not sure how you could actually use them.
If I need to splice small AWG aluminum to aluminum or aluminum to copper, which thankfully is a rare occurrence for me, I use the AlumiConn set screw type connectors and a torque screwdriver, so as to make it a UL Listed splice. These still can take up a lot of room in a box, but IMO they are presently the next best alternative to the actual Copalum splices

One thing a lot of people seem to ignore is that most lugs are aluminum. It would seem (as Alcan, among others will say) aluminum wire performs better in these lugs than copper.

I typically use compact aluminium SER just for feeders. In residential, strictly copper in comerical.

We still see circuits for heat pumps/AC units and electric furnaces wired with aluminum SE cable here. This is especially true in newer construction. I haven't checked the price difference between 2/3 SEU in copper vs: aluminum in quite some time. Copper seems to be the norm for ranges and dryers though.

Tin plated, I think.

Not the ones I see. They are solid aluminum alloy. Scratch one and see.

The only tin plated ones that I've ever seen are copper and are only rated for copper conductors. They are just copper lugs that look silver.

I have never seen a contactors in an air conditioner condenser that is suitable for Aluminum wire terminations or for that matter a cooking appliance. That's why the cooking appliances have whips and the air conditioners are wired to the disconnect with Aluminum and the whip from the disconnect to the condenser is copper. I've not seen any contactors that say suitable for aluminum wire. Maybe I've led a sheltered life but I doubt it.

I agree, I was talking about the "CU/AL" lugs and bus bars in the panelboard where feeders land.

http://ecmweb.com/mag/electric_copper_aluminum_lugs/

There are numerous situations where the equipment will specify "Copper conductors only". I've had inspections where the contractor will install a lug that is CU/AL rated and attempt to use Aluminum wire. Won't pass under my watch. I recently (about 3 mo. ago) had a steamer made by Jucuzzi that specified 105° Copper wire for the hook up to the appliance. Contractor had to hustle around and find said wire in #6 awg.

Did the topic change or am I misunderstanding the replies?

Can someone give me an example of applying section 110.5? Why is it in the code?

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.