Aluminum branch wiring?

[Gerald Wilcox]

I believe that the older conductors near the center of the pic are aluminum branch wiring. I see no evidence that this is tinned copper. Only one circuit in panel was like this, although there is some evidence of k&t left in the residence. Would you agree?
Thanks

[Jerry Peck]

Looks like tinned copper conductors with rubber insulation.

Nothing wrong with the tinned copper, the problem is that the rubber insulation is likely dried out and no longer sufficiently effective as insulation if one were to test.

[Raymond Wand]

The bare ground wire sure looks like Alu.

[Gerald Wilcox]

Thanks Jerry, I may have been overly concerned,on the ungrounded conductor where the insulation was stripped off and the conductor was exposed, at the point where the stripping tool marks were observed, I didn't see any copper.........The point you made on the insulation is well taken.

[Robert Meier]

Looks like tinned copper to me too.

[John Kogel]

I see copper, tinned copper, but no solid Al. The stranded range circuit ground is not clear, but those are old cloth-covered conductors, and we're not concerned about the stranded stuff anyway.

Sometimes the camera flash can wash out the copper color and make you panicky after the fact. :D

[neal lewis]

Gerald, how old do you think that wiring is with the cloth wrap?

[Trent Tarter]

It's tinned copper. Aluminum branch circuit wiring will have plastic sheathing like modern Romex.

[Gerald Wilcox]

Thanks for all the help! > Neal it's hard to say, it's the only conductor left at the panel not upgraded, not counting the stove. The panel was upgraded as well........my guess is the 40's. Trent makes a good point about the insulation being plastic on solid aluminum conductors.

[Garry Blankenship]

I would not agree. Someone here may know for sure, but during the time period of rubber insulated conductors, ( RH, RHW etc ), with that cross link or weaved jacket were in use I do not think aluminum conductors were available. Making aluminum requires a lot of power and we did not have enough electrical capacity then for adequate mass production of aluminum wire. I cannot say it was never made, but I have never seen aluminum conductors insulated like that. 10 to 1 that those conductors are tinned copper.

[Don Hester]

Like Trent stated I look at what the sheathing is. This looks like tinned wires to me also. Not uncommon in that 40's era.

They tinned them to prevent the reaction between the copper and the sulfur in the rubber which caused corrosion. Also the copper would adversely effect the rubber. Sort of a win win.

They still use tinned wiring in electronics and marine applications. FWIW:)