Connecting CU & AL wiring together

And expect to pay near $3 per nut. But they come with the antioxidant goop inside.

KC

So I finally saw my first aluminum wiring today.

Have heard about for years, of course, but this is the first time I'd actually seen it in the wild. Working on an apt. complex built in the late '70s; client asked me to wire the bath exhaust fan to the light switch so the fan would come on with the light (bath walls were covered with mildew, another of today's tasks of which was to remove).

Upon opening the box, I could see what at first looked like tinned copper leads, but sure 'nuf, they were aluminum. So OK, clearly I wasn't just going to put in a copper pigtail there and call it a day.

Thinking I had to buy some kind of special connector to attach the CU to AL, I went to the local hardware store (Orchard Supply), where I was shown a little tube of stuff from GB (Gardner Bender) called "Ox-Gard" that you just schmear on the wires and connector to inhibit corrosion. Cheap and a neat solution. (It's black. Looks kind of like roofing cement.)

So I actually learned something today.

From my understanding the "special nut" is just a nut with the sealer in it for expediency.

On 4/3/2010 4:42 PM zxcvbob spake thus:

Interesting: the instructions for the goop just say to use it on all wires and the connector, which I did. Isn't the metal inside regular wire nuts steel or zinc, which should be compatible with both CU or AL?

If necessary I'll buy a "special" wire nut and replace it next time I go back there.

You can read two different opinions about the Ideal 65 "twister" The U/L says it is OK and the CSPC says it is a fire hazard. The opinions spin off from there. The other method available to the homeowner and most of the trade is the King Innovation Alumicon device that is basically a 3 hole bus bar with an insulating cover.

I would use the alumicon device

The alumicon device is the same technology as the bus bars in your panel and there has never been a problem with them.

Second choice would be the twister if it was a low current application. Another option if a receptacle is present is to use a CO/ALr device with copper on one set of terminals and aluminum on the other. If you are doing the whole house AMP/Tyco makes the CopAlum splicing system that CPSC seems to like but it is a proprietary connector that needs a special tool and a certified installer. I have always been curious about the lobbying that took place when CPSC said CopAlum was the only method they would endorse (prior to the Alumicon)

On 4/3/2010 7:18 PM snipped-for-privacy@aol.com spake thus:

So what would you do if you needed to connect a CU pigtail to AL wiring?

Aluminum wasn't used much for branch circuits until about 1965 when copper prices went up. There were enough problems that about 1971 UL removed the listing for wire, switches, receptacles, wire nuts, ... then put out new standards. The new switches/receptacles are marked CO/ALR. The vast majority of installed wire is the "old technology" stuff. Use died out about 1973.

Because of the problems the CPSC started an investigation, and tests were done which included thousands of connections in various combinations. The engineer that was behind the testing has a paper on aluminum connections at:

For splices he recommends Alumicon connectors:

The only other UL listed connector I know of is Ideal #65 wire nuts. The author specifically is not fond of them. One reason, if I remember right, is the metal the spring is made of. Details are in the paper.

Before Alumicon, the author had an older paper:

The problems were only with 15 and 20A branch circuits. Aluminum is often used in larger sizes like service wires. The connectors bite into the aluminum, which as gfretwell notes is similar to what happens with Alumicon.

Here's my take on the subject, from someone that owned a house for 36 year with several 15/12ga aluminum branch circuits. When they 1st started having problems in the early 70s, it was said to used switches and receptacles rated for Al. They then came out with the CuAlr stuff. I don't know what the older Al rated stuff was, but they said the CuAlr was different. I know the screws where bronzy looking. All of the problems I saw, in my neighborhood, were on circuits using the "push-ins" instead of the screws to daisy chain outlet to outlet. 3M, at the time, came out with a wirenut that was listed as connecting copper to aluminum. Also, the crimp connector, mentioned in this thread, was eventually claimed to be the only acceptable way to deal with the problem. That all said, I used the 3M wirenuts (there was no goo in them) to pigtail all my connections. I never had a problem, but many people that never touched their wiring didn't either. The wirenuts produced today by 3M look the same, but don't mention aluminum, as far a I know. I have used the 3M units in my house exclusively. I think, emphasize think, most of the problem where the push-in terminals. And, I think, most of the bad press for the push-ins was probably related to aluminum wire usage. In my subdivision, the early houses used aluminum with push-ins: problems. The next vintage house used them on regular outlets, but on screws; I never heard of problems. The 3rd vintage used CuAlr outlets; never heard of problems. These are just my random thoughts, YRMV from this.

That's pretty much what I've heard. That aluminum doesn't like to be backstabbed.

Yes, that Ox Gard (I fondly call it Ox Gored) is good stuff. Also helps with copper connections, like outdoor electrical work. I use it in my work, repairing outdoor equipment.

We had a good presentation from AlCan at one of our IAEI meetings. They point out the original wire was alloy 1350, the same wire they used for overhead transmission lines, and it was not engineered for the kind of service you have in device wiring. It broke easily and the thermal expansion rate was higher. The new AA8000 is stiffer and has a better thermal coefficient. The CO/ALr device does, in fact, have a different screw. They are not steel, they are a brass alloy that closely tracks the expansion rate of the AA-8000 alloy. There are also ridges in the base that bite into the wire a bit. When you get to the lug type devices (bus bars etc) they are generally aluminum in the first place so they don't have any expansion issues at all. They actually perform better with aluminum wire than with copper in tests.

Then there are the stupidly expensive crimp-on copper pigtails ---

Use the Schmutz and a wire-nut. - or the Ideal "65"

On 4/3/2010 8:13 PM snipped-for-privacy@aol.com spake thus:

Except that this is inside a *switch box*, remember? Fully populated with two duplex devices (receptacles and switches) and a bunch of wires, so no room for such a device.

Well, I guess it's low current: one wall light fixture and a ceiling fan.

Anyhoo, I used the wire nut + goop approach.

On 4/4/2010 6:07 AM Stormin Mormon spake thus:

Getting biblical here, it all depends on whose ox is being gored, right?

But, of course. I'd have thought that the ox is the creature doing the goring. The victim, naturally would be someone like a Mexican torreador, or the american tax payer, or someone relatively innocent.

In any case, it's good for aluminum wire, and many other applications. I've been known to put a shot of Ox Gored on copper connections, when exposed to the weather. I do work on outdoor equipment. It's some what protected, but not totally.

If there is not enough room inside the electrical box that is in place, then replace that box with a larger one which has more room in it...

If the walls are open you have many ways you could deal with this...

A 4" square box with a 2-gang trim ring sounds like a good idea if you have the wall open and need more room inside than a standard switch box...

~ Evan

Far as I know, backstabs were never approved for use with aluminum. They have enough problems with copper - they should never be used with aluminum. You can't use the ones available now because the #12 aluminum wire used for 15A circuits doesn't fit any more.

UL changed the standards about 1971. I don't know if 3M was listed for aluminum before, but only Ideal 65 wirenuts are now (and Alumicon, which is not a wire nut).

From extensive testing on aluminum connections, 3M Scotchlocks were recommended, used with antioxide paste and techniques detailed in