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Question:

connect copper to aluminum?

I need to fix some connections at my dad's house. The original wiring is aluminum, but the newer stuff he did is copper. Simple wire nuts will not suffice. Already had one melted one. I need to fix the connections, but need an economical, safe way of doing it. Suggestions?

Answer:

Not a good idea. Replace the aluminum. The metals can react and heat up.
It is safer to replace aluminum with copper. Joints between copper and aluminum tends to oxidize and overheat Electrical fire may happen because of it. In aerial installation, copper is joined to aluminum by means of compression lugs and the lugs screwed together with dow corning compound as anti-oxidant compound
Replace all the wires into copper. Risk of fire as copper joints with aluminum or cause intermittent problem use on heavy current load. Because copper twists joint with aluminum create thermo effect. Aluminum wire was abandoned for house wiring long long time ago.
The wire on the exit signs are silver in color but are probably not aluminum, usually having some content of nickel causing the silver appearance. But I can't see the wire over the internet, but if you really think they are aluminum you need to find connectors that are labelled cu/al that have a special antioxidant contained in the connector. If they aren't aluminum the special connectors won't hurt a thing.
You need both anti-oxide paste, (follow directions), and spring type connectors to take care of the thermal creep.- A good electrical supply hose will have them. Give them the details and they'll advise you. (Last I heard, modern wirenuts are ' UL listed' for the application. Lack of the surface treatment is probaly the cause of your bad connection.) Aluminum wiring isn't bad by itself. It's the terminations that cause the problems. Bad advice Shabir - Screw connectors have no 'spring' to take up the thermal cycles of the aluminum and are exactly the WRONG thing to use for the problem in question.

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