Mixing Al and Cu wiring

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  #1  
Old 03-04-11, 10:40 AM
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Mixing Al and Cu wiring

I have some questions related to my house wiring. I have an older house with conduit. The old wiring looks to be aluminum with the cloth insulation. I have been slowly replacing the wiring whenever I put in a new fixture/outlet/etc. I have been pulling the two conductor copper wires through the conduit and mixing it with the aluminum. I recently watched something where they said that was a bad idea. The corrosion idea I get, but they said there was a heating problem with the aluminum. The previous owner(s) did this too. Is this really a huge deal?

Second question. I've noticed the main conduit to the second floor has romex running through it. I have also read that this is against code in some areas due to a heating problem. Is this a huge danger?

Last. There is no ground wire running through the conduit, but I know the conduit itself acts as a ground (it is grounded near the box). Would I be better off running a ground as I am pulling wire through?

Sorry for all the questions! I live in Rochester NY if that helps with codes.
 
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Old 03-04-11, 10:59 AM
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Originally Posted by cheese9988 View Post
I have been pulling the two conductor copper wires through the conduit and mixing it with the aluminum....Is this really a huge deal?
Yes it is really a huge deal. Copper and aluminum expand at different rates, so as current flows through and the wire heat up, the connections work themselves loose. The gaps between loose connections arc, corrode further and eventually melt or burn. There are only two connectors that successfully join copper and aluminum: Alumiconn and COPALUM. Alumiconn you can do yourself, but COPALUM must be installed by an electrician. Given that you have conduit, it would be much better to simply scrap all the aluminum and replace it with copper.

I've noticed the main conduit to the second floor has romex running through it. I have also read that this is against code in some areas due to a heating problem. Is this a huge danger?
To my knowledge is it not against code, but many electricians believe it to be a substandard quality work (use the right material in the right place). I do not think of it as a safety problem.

There is no ground wire running through the conduit, but I know the conduit itself acts as a ground (it is grounded near the box). Would I be better off running a ground as I am pulling wire through?
Some conduit can act as a ground. Solid metal conduit like threaded pipe or thinwall EMT conduit is a legal ground when used as fully assembled system. That means tight fittings, all metal boxes and no breaks in the system (rusted through, replaced section with PVC, etc). Flexible metal conduit (corrugated, Greenfield) is not a legal ground anymore so you should pull in a separate ground wire.
 
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Old 03-04-11, 01:25 PM
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The old wiring looks to be aluminum with the cloth insulation.
Rubber/cloth insulated wire is more likely to be tinned copper than aluminum. Try scraping the wire and see if it is copper underneath the silver color. You can also look at the end of a freshly cut piece to see if it copper.

If you do have tinned copper there is no problem splicing it with the new copper.
 
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Old 03-05-11, 08:30 AM
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Like Furd I think the OP is dealing with tinned copper. Aluminum came with plastic insulation.

Since you have a conduit the OP can use individual conductors instead of the harder to work with NM cable in the conduit.
 
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