My new house in the US has a Harbor Breeze combination fan/light switch with a remote control as seen here (different brand is shown, but it's basically identical). While checking some wiring (unrelated), I pulled the switch out of the wall and saw to my surprise that the wire leads coming out of it appeared to be aluminum (the house has copper wire). The wires aren't visible in the previous link, but you can see the same thing here on the page for the receiver. My understanding is that aluminum wiring is no longer done residentially and that it's a very bad idea to mix copper and aluminum unless you really know what you're doing. So what gives? Are these wires not actually aluminum, or are switches an exception for some reason?

Edit: In response to requests for more information, careful visual inspection doesn't reveal any copper color, even in cross-section, but the wire is braided and the individual strands are so thin that it's difficult to even see the cross section. That in itself probably rules aluminum out. Markings on the wire are:

E108485-S 18AWG FTI -F- REI HSING CSA TEW 105oC 600V LL84687 AWM 1015 VW-1

Those codes led me to this pdf, which says "tinned Strands, copper conductor, 7/0.254mm strands." So I guess that's the answer. Next time I'll know to search for the codes before bothering people here. :)

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    If this is a modern switch, my suspicion is that you're seeing a twisted copper wire that's been tinned with solder. Can you try and pull the wire sheath down a tiny bit and see if you see copper? Actual pics would help. – Aloysius Defenestrate Oct 12 '15 at 14:07
  • @AloysiusDefenestrate I'm not there to take a picture right now, but your comment set me off investigating tinned copper, and I'm pretty sure that's exactly what it is. – dlf Oct 12 '15 at 17:03
  • Look at the ends of the wires, if they are tinned copper, the cut end will be copper colored. That type of tinned wire isn't tinned only at the ends but each strand is tinned along its entire length before being combined and coated in insulation. – Dan D. Oct 12 '15 at 19:35
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    @AloysiusDefenestrate, you can post that as an answer if you want since it looks like you were right. – dlf Oct 12 '15 at 23:02
  • You can post your findings as an answer, and then accept it. That way if others come along with a similar question, they'll find an answer. – Tester101 Oct 13 '15 at 13:32

Modern switches with leads will sometimes have normal copper wires that have been tinned with solder.

Nip a tiny amount off the end of the wire, and you should see copper if this is the case. (Thanks to @Dan D for this tip.)

  • I couldn't see the copper color (strands were too thin), but investigation of the codes printed on it revealed that it was indeed tinned copper (see edits to question). – dlf Oct 13 '15 at 15:24

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