aluminum vs copper clad wiring

Did an 80 year old house a few months back and the panel had what appeared to be aluminum wiring. The client had an electrician out to look at rewriting and he said that the wiring was copper with a cladding. Client needs something from me as the lender which is rural housing will not accept his electricians call that’s it’s copper with cold coating.
Anyone have any experience with this?
Told him I did a visual no invasive inspection and that it seemed to me the electricians determination would trump my visual observation but his lender insist that I verify?
Any advice?
Electrician will be there today and I thought I would meet him just for observation

Aluminum wiring will have plastic sheathing.

The aluminum wiring to be concerned will typically have been installed in the late 60’s-early 70’s.

Tinned copper will be cloth covered.

You can etch/scratch the wire. If it is tinned copper the copper will show. Also Aluminum wire is softer.

Based on the age it is tinned copper.

The old rubber insulation that was common 80 years ago was reactive with the copper conductors so the copper was coated (tinned) to prevent any reaction. As Chris and Jim stated if it’s 80 years old it’s not aluminum.

Aluminum would also be one gauge larger that copper of the same ampacity.

I always look at the end of the cut sections of the wires where you can see the copper exposed where they cut it.

Most good electricians around my area will scrape the neutrals so that you can see the copper. You can always have the electrician do that and you look at it afterward.

Thanks!! Just got an education from the electrician as well. First time I have crossed this but am now a little wiser . I appreciate all the clarification and info… Very helpful

Actually…I tends to be about two gauges difference in most cases.

For example - 1/0CU @ 90 is 170A versus 3/0AL @ 90 is 175
6 CU @ 90 is 75A versus 4 AL @ 90 is 75

So (just the wire guy in me) it generally runs about 2 gauges different…

Now this runs true in larger conductors for the most part, in smaller conductors like Jim is speaking about it slightly less true…but still true. (make sense…lol)

For example - 10 CU @ 90 is 40 A versus 8 AL @ 90 is 45 A

So technically it is one potential gauge in between…but in actuality it’s two theoretical differences in gauges between them. Now, with that said we don’t make 9 AWG (someone might…lol)…we don’t but I figured Jim’s post led to me explaining in a little more detail as I never miss a chance to elaborate…we all know that.

Paul, thank you for being such a valuable resource on this site.
I know that aluminum alloys have come a long way since the 60’s and the 70’s…
Do they use aluminum wire these days for branch circuits?
I know it’s in wide use for feeders and service, but what about branch circuits, at least in larger gauges?

I was referring to the smaller branch circuits where a 15 amp circuit on aluminum would be #12 and a 20 amp would be #10 whereas copper would be #14 and #12 respectively.

Based on the age given, it most likely is tinned copper. Aluminum wire dates from the 70’s

I know…but I could not miss an opportunity to talk about wire and cable:twisted: