Electrical contact question -- kitchen cooktop

And I think it is 99.9999 % NOT likely that you have aluminum wiring in the house.
Just LOOK at a bare wire end.
Aluminum does not LOOK like copper.

 

Installers made the move away from copper when the price started to enter the upper stratosphere. I am no electrical guru, and I am not familiar with the product mentioned, but you do need an antioxidant when you use aluminum. It creates a severe fire hazard, otherwise.

 

If that was less than 40 years ago, you need to find a new electrician.
I don't think that any ethical one uses aluminum wire these days.

I thought it had been banned nationwide a LONG time ago.
Maybe not.

 

any luck when googling the requirements? my results turn up anti oxidant grease. ideal is a big electrical manufacturer.

 

@jerrymildred might be the guru for this.

 

That is my understanding as well, that older houses may have aluminum wiring to the 220 volt receptacle and modern appliances have copper wires.

I used an electrical grease like the one you linked to attach a new 220 volt receptacle onto the ends of my aluminum wiring to my range. So far, knock on wood, there has been no problem.

Posted via the PriusChat mobile app.

 

Our house is about 25 years old, and definitely has aluminum wiring to the 220 volt original range location.

Posted via the PriusChat mobile app.

 

During the time EC alloy aluminum wire was in use, millions of houses were built with it. No-Ox-Id is good stuff but not sufficient (oxidation is only one of the ways aluminum wire terminations fail). The main requirements come from this section of the National Electrical Code:


Breaking that down a bit: (1) you can't connect the aluminum wire directly to the terminals of your cooktop, unless those terminals are clearly identified as suitable for aluminum. Historically, two different designations have been used. Back in the '60s/early '70s, there were devices marked AL-CU that were believed to be suitable at the time, but a lot of fires proved that belief wrong. The new designation introduced after that was CO/ALR, and that's what you need to look for on any device that you're going to hook to your aluminum wiring.

(2) If the cooktop doesn't have CO/ALR terminals, you can use short pigtails of copper wire (of the appropriate gauge), connect those to the cooktop terminals, and splice them to the aluminum wire, using splice connectors listed for that specific use. There has to be room in the junction box for the extra wiring and connectors. Other sections in the code specify "maximum box fill", or how many wires and connections, of what gauges, are allowed in a box of a certain cubic-inch volume. It's not just "how many can I fold and pack in there" because heat has to be taken into account, so possibly you'd end up retrofitting a larger box into the wall.

(3) You can also see, in the code excerpt above, that the splicing connector between copper and aluminum isn't allowed to let the two metals touch. It has to be of a design that clamps them both, but separately. Generally like this thing. There appears to be one exception, though: according to the 2008 NEC Handbook (p. 47), "On February 2, 1995, Underwriters Laboratories announced the listing of a twist-on wire connector suitable for use with aluminum-to-copper conductors ... (t)hat was the first listing of a twist-on type connector for aluminum-to-copper conductors since 1987." The Handbook doesn't plug it by name, but it's apparently the #65 from Ideal, a twisty wire nut that's color coded purple and supposedly ok for the job, but if you google it even slightly, its reputation is not good. Another technique is a special crimp connection, "COPALUM", that keeps the two conductors separate, and is crimped by a special crimp tool, wielded by a COPALUM-certified electrician.

So for DIY, probably the Alumiconns listed above are easiest. From what I read, they come pre-dabbed with an antioxidant gel, so you don't even need a separate tube of No-Ox-Id. You should make sure you have an inch-pound torque driver (which you may have already for hacking on your Prius), to make sure you can follow the connector's torque specifications closely. Every detail of connecting aluminum to copper is serious.

Speaking of Prii, Toyota also uses aluminum in some of their wiring. They generally also color-code the aluminum wires purple, and they also have special crimp connections and heat shrink covers, with their own matching crimp tool, and painstakingly specific instructions for doing any splicing on the stuff.

-Chap

Here's a longish but fascinating historical article on aluminum, and later copper-clad aluminum, in branch circuit wiring.

 

The Toyota Wire Crimper SST (09042-2C100), from photos in service bulletins calling for its use (PDF), is just a Lobtex AK15A with a high markup (list price ¥10,100 or $130.25). I bought one for $40 or so from Mutsuura Honten Co., Ltd. (established 1892) on Rakuten; it’s a high-quality (made in Japan, JIS mark), controlled-cycle tool for hand crimping of non-insulated splices.

 

Nice, @ChapmanF!

I don't blame the installer for shying away, but you'd think they would have checked to see if the wires actually were aluminum. But it looks like you've confirmed that. In that case, I agree with Chap. In fact, I'd suggest a licensed electrician do that job for you. They have special crimpers like this for aluminum to copper connections.


Or else you can use something like what Chap suggested, but will need to use some sort of torque driver for the screws.


By the way, I know you must be frustrated, but those codes are there for really good reasons. I only wish they had never permitted aluminum wire to begin with.

 

Take a file, emery cloth, or even a blade to it. Copper wire can be coated with a silvery metal(tin?).

If it is aluminum, I found this site informative.
Aluminum to Copper electrical connectors

If the outlet isn't CO/ALR, replace it. Corrosion on aluminum overheating is only part of the issue. The other is that aluminum expands more than copper as it heats. This causes the connections on an unapproved receptacle and switches to loosen overtime.

Noting where you live, I'm guessing it was cheaper than copper. For the mainland US, the '60s and '70s was the period aluminum was mostly used in new homes.

 

Thanks. I forgot to mention that.

Another tip. I always go back after I get done terminating copper wires and usually get another quarter turn or more on the terminal screw, especially with solid strand wire. It seems that the copper must relax a little or something.

 

I suppose you'll know more once you duck under there and look. If you find copper cooktop wires running down to aluminum branch wires and connected using some things, you can snap some closeups of the things, and see what kind were used.

I can think of a few possibilities... if you find things that are separate-screw-clamp deals like the AlumiConn connectors shown above, and they're in purple insulation with clear manufacturer's marks and approved for the use, they'll be reusable. Grab your inch-pound torque driver.

If they turn out to something like the Copalum crimp connectors, you can't reuse those, they're crimped. You could cut them out and have them redone (takes an electrician certified to use the power Copalum crimper), or just cut them out and replace them with AlumiConns. Or maybe it would be easier to just cut the old copper and splice to that, which needs no special precautions. Maybe the existing copper pigtail is long enough to reach all the way to your new cooktop terminals ... problem solved.

A grayer area is if you find whatever was used 7 years ago to join the al to the copper, take your closeups of it, and it doesn't turn out to quite be anything approved for the use. That never happens, of course (cough). In that case, you'd have a good opportunity to re-do it with something that is.

-Chap

 

If its AlumiConn or Copalum, I'd just cut the old cooktop wires and connect to them. No need for grease or anything else.

 

Just a 'shade tree' approach, I left the cover off the junction box and tested the connections using an IR thermometer to measure the heat with the stove top at max power. Not seeing a temperature rise after 10 minutes, I turned everything off and put the cover on ... about 15 years ago.

Bob Wilson

 

Did you also have aluminum-to-copper splices going on there, or were you just looking for a reason to use an IR thermometer?

The sneaky thing about Al/Cu junctions is if everything isn't Just Right, they don't necessarily stay the way they were 15 years ago.

-Chap

 

No and yes.

I used the same technology that the original range wiring used, wire nuts, only new ones.

Agreed but heat is a good indicator if something is going wrong.

Bob Wilson