cu to al wiring


Old 09-16-01, 07:22 PM
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need help.... a house that i'm working on has all aluminum wiring and I am trying to install a new free standing stove that is rated for copper but can use al wire with a special splicer. My question is this....I installed a new gang box with a new leviton 50 amp 3 wire outlet that is rated for cu or al wire. then I install a new 50 amp rated stove cord\pigtail that is copper .... my point is, is this outlet I'm using the splicer that the back of the of the stove says to use when going from cu to al....any help please
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Old 09-17-01, 06:35 AM
Lou Wasnesky
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I would...

I'm going through the same hell in my house which is mostly aluminum wiring. From my research there are three options:

1. Use the "cop-alum" connector made by AMP. This however has to be performed by a certified technician and can cost up to $40 per outlet/fixture. AMP won't sell this stuff to the general public. It is the only recommended treatment by the CPSC.

2. Use Penetrox-A on the aluminum by first sanding the aluminum with very fine paper, then placing some of the Penetrox on it, sand further to work the chemical in, twist the aluminum and copper together, and finally place a wire nut on the connection. Please avoid any of the Ideal brand treatments. Their version of "Penetrox" is flammable (I tested it). A company named "Burndy" produces "real" Penetrox-A. I had a heck of a time finding it though.

3. Run a new copper circuit.

For something as high-current as a stove is, I would run new wires.
Old 09-17-01, 06:38 AM
Lou Wasnesky
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Didn't read the part about already having put in an aluminum rated outlet. I would still treat the aluminum wires attached to this outlet with the Pentetrox as I explained in my original post. That should be all you need to do. Just plug the stove into the new outlet.

Personally, I would still run the new circuit. For regular outlets powering lower-amperage devices I am using aluminum rated outlets. For anything else if it's not copper, I am rewiring.
Old 09-17-01, 01:27 PM
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The range receptacle will allow you to connect aluminum wire to that receptacle. The the pigtail is supposed to be copper that is plugged into that range receptacle and the free staning range.

However you have an NEC violation in running a three wire, three prong circuit in a new installation whether aluminum or copper.

A new range circuit must be at least 40 amp rated with 6 awg aluminum or 8 awg copper as the minimum size conductors on a 40 amp breaker. Most people run 6 awg copper or 4 awg aluminum using a 60 amp breaker.

In new branch circuit installations serving an electric range requires a red, black, white, bare conductor in that cable serving that new branch circuit with a four prong receptacle and a four wire pigtail.

Either way the aluminum to copper transition happens at the receptacle where the lugs connecting the conductors to the receptacle accepts either aluminum or copper conductors. The pigtail is copper conductors.

If you install a three prong receptacle on an exisint SE type cable then you must make sure a bonding equipment grounding jumper is installed between the neutral of that connection block inside the range to the metal shell of the range.

If you install a new branch circuit you must install a 4 wire cable with a 4 prong receptacle with a 4 wire pigtail and the bonding jumper is removed inside the range connection block from that connection block to the metal frame of the range.

Hope this helps

Old 09-17-01, 02:16 PM
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Lou Wasneski, the larger the aluminum conductor the less trouble you have with the connections. If you have an older home that has the smaller awg conductors such a 12 awg then the current NEC allows these aluminum conductors in size 12 and larger to still be used today as a building wiring method.

The devices on the market today are better designed to accept aluminum wiring in the smaller gauge than the older devices. Many brands of wirenuts are approved for use with aluminum or copper. Be careful to read the manufacturer's instruction before you add anti-oxidation inhibitor on a connection. Many wirenuts already have inhibitor inside the wire nut. If you add a different inhibitor and mix the two chemicals you possibly can get a reaction causing deteriation of that connection or even causing a heat source that could start a fire. This often happens when mixing different chemicals together.

Be careful and read the manufacturer's instruction before applying an anti-oxidation inhibitor. You may be creating a hazard instead of limiting a hazard.

Good Luck


Old 09-18-01, 02:07 AM
Lou Wasnesky
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As for my house, I am using 3M Scotch-Lock wire nuts that do not contain any inhibitor. So, different chemicals are not being mixed. For the most part I am avoiding pig-tailing by replacing existing switches and receptacles with aluminum rated ones. I still use the Penetrox on the aluminum even with the devices as has been recommended to me.

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