Recently I was troubleshooting/repairing parking lot plugs in a fenced compound used exclusively by a school bus company. All of the wiring, starting right at the panel, was Aluminum. This was not an older installation and based on the overall appearance of the parking lot I'd say it was a "money saving" installation in every which way possible. It's not often I find Aluminum wiring unless it's in a house that was built in the 70's. The only time I've heard of Aluminum being the preferred choice in recent years was when I was still in school. One of my instructors said that Aluminum was a reasonable choice for residential service conductors because it's cheaper. I remember a few classmates taking issue with that comment. Anybody here use Al for certain jobs?

For larger feeders (2ga and up) aluminum is pretty common. I haven't seen any small conductors used for years. (early 70s)
The real problems involved screw terminations and the metal used in the screw but the reputation killed the product.
A lot has been installed, trouble free, using lugs. Aluminum wire in an aluminum lug, as most are, may actually perform better than copper.
It all has to do with the expansion rate of the 2 metals.

IMHO - Thin Aluminum is only appropriate for siding houses and wrapping leftovers.

It has no business being energized.

I don't think that Sask Power uses any copper in its feeders. Because of that, we have a pretty good history that aluminum feeders aren't a problem.

Pot:
Are you saying that you have devices wired with Al conductors, or are the repairs in the feeders???

Over the years with tools, I had a few issues with Al conductors (#4 & #6) that were installed for parking lot lighting circuits. Deterioration from the water (UG) over time caused burnouts, and it was a PITA to make repairs.

Cracks or scratches in the insulation allowed corrosion, and over time...burnout and fry the PVC conduit.

Budget saver when installed originally, but a budget buster on repairs.

I don't like AL for anything under 100A, either AL or CU conductors will have problems if installed improperly.

The repair was all over. The Al neutral feeder had come loose at the first pedestal, closest to the panel, and as a result it was creating the inevitable whacky voltages further down the line. Even the receptacles themselves were connected with Al and they weren't Al rated devices. Some of those connections were broken but not obvious. Overall a real messy install that I thought was done to save money.

Problem in the post was the aluminum strands were thin and round thus would get smooched, even with proper touquing. I don't use aluminum wire for branch circuits but have used compact aluminum wire for feeders.

Nice thing about compact aluminum is the strands are not round but shaped in a manner so there is no gap in between the strands plus are much thicker so they stand up better when torque. Generally you do not have to use larger conduit in order to get the same ampacity as its copper equal.

With Aluminum back ground, it's a hard sell. I'll use it for residential feeders and that's about it.

Al was used extensively all over Eastern Europe until at least 1990 and I'm talking as small as 2.5 mm2 (slightly larger than 14 AWG). Sometimes with crimp splices, more often with screw terminals. Problems are far and few in between, particularly with DIYers stuffing aluminium and copper into choc blocks. I once looked through a 1970s place with a mix of Al and Cu (but never under the same screw and all socket circuits were copper, only the lights were Al) and there were no obvious problems. I did re-tighten some screws but that's what I'd expect in any install of that age. The Al alloy used for domestic wiring does break more easily than copper and has to be treated with care. In Austria Al was only used for a brief period during WWII so any you'll find is well past its best-before date anyway. Currently Al is limited to 16 mm2 and up by the regs and only used for large feeders, always with crimp splices and by trained professionals.

BTW, the Germans are very happy with Wago connectors and 2.5 mm2 Al (loads up to 16 A), provided the connectors are filled with their Alu Plus paste or vaseline.

Considering the hype, it amazes me how many million houses built in the late 60s and early 70s that didn't burn down

As I said, if Al was indeed inherently dangerous, Europe east of the Berlin Wall wouldn't be standing any more. It#s definitely more difficult to install and maintain than copper and therefore dangerous in the hand of DIYers but that's about it.

Proper push-in terminals completely take the issue of deformation under screw heads out of the equation, that's one advantage of current continental European wiring methods and accessories. Screw terminals are essentially extinct in domestic wiring and have been for some 15 or 20 years. Hager introduced push-in neutral and earth bars 5 years ago and I haven't heard of any issues with them and Wago makes push-in connectors for conductors up to 6 mm2 and 40 A.

I've never had a problem at all with aluminium wiring, it's used for larger loads here like sub-mains and the like.
And provided you use the correct crimp connectors and the right crimp tool, there should never be an issue with them.

Half the problem I believe is when aluminium conductors get terminated under screws and in tunnel terminals, which is not what should be happening.
Because aluminium is such a ductile metal, the individual strands will "flow" away from the tensioning force on the screw that terminates it.

Any aluminium conductor should be terminated in the proper Al/Cu crimp connector with either a fork or an eyelet on it before terminating it where it needs to be connected.

I assume you mean these for "tunnel terminals"

That is the standard "lug" here and they seem to work fine.
Our problems were with binding screw terminals and that was really when the screws were steel. Brass screws work fairly well in the CO ALr devices

If they aren't some sort of a shear-bolt design, with them Allen head stubs, no that's not what I'm referring to.