Latest Discussions : Electrical & Lighting

Lawrence

10:16AM | 12/12/00
Member Since: 11/14/00
333 lifetime posts
I have a condo built in the magnificent 70s with lots of aluminum wire that I will need to join with copper wire to do some rewiring and add some fixtures. I know that joining aluminum and copper wires requires a special joint including some special putty, but three questions remain.

First, why? What specifically will happen between copper and aluminum (besides just "fire")?

Second, I have also heard that the junction needs to be exposed to air, so a neighbor of mine has left his copper/aluminum wire junction box open and exposed inside one of his kitchen cabinets. I think he got "exposed" confused with "accessible," meaning that the box does not need to be exposed to air but also should not be, say, hidden behind drywall or something so that they can be serviced when necessary. Is that correct, or do these junctions need air exposure so as to not burst into flames? I would think that "exposed" would be more of a hazard.

Third, how necessary/useful would it be to undertake a complete rewiring and replace the aluminum wire with copper wherever possible? Is it something that I should not bother with, or is there a reason beyond mere efficiency that aluminum has completely fallen out of vogue? (safety...?)

ElectrcBil

07:38AM | 12/30/00
Member Since: 07/21/00
76 lifetime posts
First aluminum and copper have different galvanic properties. They will tend to corrode each other. Second, they have different heat coefficients and will tend to expand and contract differently, this makes it extremely tough to connect them together securely. Over time they will loosen. Aluminum expands and contracts much more than copper. Aluminum also oxidizes when in contacts with air, this makes the connections corrode. The paste that is applied is called "Nolux" its purpose is to keep the air off of the Aluminum. You should only use connectors with aluminum and copper that are "listed" and "approved" for joining Aluminum to copper. All devices terminated with Aluminum wire must also be listed and approved.
As for how difficult it is to rewire a house, It depends on the house. It can be very difficult and exspensive. It is one of those things often better left to a professional. I hope this helps.

ElectrcBil

07:51AM | 12/30/00
Member Since: 07/21/00
76 lifetime posts
Aluminum and copper have different galvanic properties. They also have different heat coefficients. This means they will expand and contract at different rates and will tend to corrode one another leaving you with a bad connection. Aluminum also corrodes with the contact of air. That is why you use the paste on all connections it prevents air from contacting the aluminum. Only use "approved and listed" connectors and devices when using aluminum wire.


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