ECN Forum Forums General Topics of the Trade General Discussion Area Aluminum

The fundamental problem with aluminum conductors is that the metal is intrinsically softer than copper.

It's less forgiving when technique is bad -- and branch conductors are virtually certain to be reworked by DIYers -- who are all thumbs.

There's a strong tendency to forget just how much of our art is due to practice and 'touch.'

Hence, copper is propper.

It is not as much the softness as it is the difference in expansion rates. If the wire and the lug do not expand at the same rate, the contact open up, resistance increases, it gets hotter and the problem keeps getting worse until something burns up.

Greg:
Thanks for the info on 'only feeders' and not branch circuits.

I think a few of us had thoughts on Al NMC!

He was pretty specific that his pitch was just for lugs and larger wire. The talk about Al romex was just answering a question.

He did pass out samples of the old, bad 1350 alloy and the new AA8030. I can see it is a lot better. When you bend the 1350, it tends to kink and bend in one spot. The 8030 takes on a long arc.
The 1350 is really only designed for aerial lines, not something you will be bending a lot. It is pretty stiff.

The 1350 stuff they used in romex was annealed so it would bend easier but they still did not address the kinking problem. The "aluminum problem" was because they use steel screws in non-co/alr devices and the expansion rate is vastly different. The co/alr device has a screw that matched aluminum better, along with being bigger and I think there is some "bite" on the mating surface to grab the aluminum.
I still would not use it. We agree there.

About 8 years ago a colleague claimed we'd soon see Al branch circuits coming back. It hasn't happened, in fact quite the opposite is true, both Austria and Germany since removed the possibility from their regulations and upped the minimum size to 16 mm2 Al (branch circuits were 2.5 mm2 and up).

Here in the UK, we had a brief tangle with aluminium (or in your case, aluminum) branch circuit cables in the late 1960s. They were however "copperclad" conductors, with an aluminium core. It was, a very short lived type of cable and we went back solely to copper for such. I still find one or two houses with remnants of this and dread doing so. It is terrible to work with and the same problems as you had, with expansion happen all too often.
As in Germany and Austria, we now have a minimum size for this metal in cable, which is way above normal branch circuit sizes.

Al was introduced around the beginning of WWII here and dropped almost as soon as the war ended. By the late 1940s all electricians were back to copper. Therefore Al is fairly rare. Feeder-sized Al was re-introduced some time in the 1990s, usually 25 mm2 and up and mostly installed by utility companies rather than electricians.

Our neighbours behind the iron curtain used plenty of pure and copper-clad aluminium in all sizes, including even lacquered Al wire for transformers. Their Al conductors break easily when nicked but problems with expansion seem to be limited. Eastern Germany moved to crimp splices rather early, but in Hungary and Czechoslovakia mainly screw-type connectors were used for Al wire. I once had the chance to go through some old wiring in Prague checking all screws and the proportion of loose connections was no higher than in any copper installation I've encountered.

I really don't have a problem with AL conductors for 100A & larger feeders, & services, installed correctly it will give trouble free service, smaller then that no thank you.

Copper is still the conductor of choice,though.