Joining copper wire to aluminum

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Old 09-08-09, 09:00 AM
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Joining copper wire to aluminum

Hi,

We're redoing the master bedroom at my parents' house. Over the weekend I discovered that the house (1960s) was wired with aluminum. I bought CO/ALR receptacles and switches to replace the old ones.

When I started doing that, I found aluminum wire joined to new copper wire in a box, with just a regular "yellowcap." Apparently this was done a couple of years ago when my mother hired an electrician to install a new ceiling fan. He took the power for the fan from a wall switch -- he just backwired the hot (copper) wire into the switch itself, and joined the neutral wires in a yellowcap, and the ground wires in a yellowcap.

Is this a safe way to join copper and aluminum? If so, should I just pigtail copper wires to regular receptacles and switches (the CO/ALR ones are $4 - $6 EACH at the big boxes!) But this really didn't look right to me. What should I do?

Thanks as always.
 
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Old 09-08-09, 09:07 AM
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Roughening up and smearing on some Oxgard paste will help. But this precaution, albeit better than nothing, even probably is not the approved method. There is a specialty tool sold for crimping the two dissimilar metal wires together, that requires some schooling to work it, the way I understand it. [ Do not use some typical plane-jane crimping tool!!] Then this joinery is approved, code wise.

Also, I believe there are actual connectors made for this. Have you asked?

I also have seen where people have made say external (not in walls) connections using those heavy solid metal tube-shape connectors(they are like maybe 1 1/2 inches long, by a diameter that allows your bare stripped wire to fit in the hollow) that have set screws opn each end that clamp down on the wires, and then with Oxgard in it, and then with that shrink tube material you shrink wrap with a lighter, and maybe electrical tape ontop of that - put over each connector (if say hot, neutral, or two hots and a neutral and ground) .That method also would have to be better than just some plane wire nut job, which you definitely wou dnot want to do! Such plain joinery will end up creating a potential dangerous heat condition from a deteriating connection after a while. And I am sure you know about this(hence your inquiry) and possible consequences. But I'm not sure if even code would approve that, say when done in some crawl space area and in a junction box.
 
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Old 09-08-09, 09:32 AM
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The crimping method mentioned is called Cop-alum. You need to lease the tool from Amp and be licensed by them to use it.

There are terminal block type connectors by King called Alumi-conn that are relatively new to the market to allow the AL to be spliced to copper.

The method used probably was not a code compliant method unless the connectors were listed for use with AL and copper.

Watch bending the AL conductors. It had a habit of fatigueing very easily and breaking off.

Older boxes tended to be on the small side also.
 
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Old 09-08-09, 09:45 AM
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Older mobile homes in the 60's and early 70's often had that, and is scary once you see what can happen with melted outlets and the more brittle aluminum wire you speak of pcboss. Knowing that trailers can burn up so fast that people often can't excape fast enough.
 
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