I've moved into a house build in 1971 which is wired mainly with aluminum wiring. I've read a handful of published information that states that aluminum wiring (or more correctly, the connections made with aluminum wiring) do in fact create a fire hazard greater than copper wire. I also know that a lot of people state that aluminum wiring does not pose any greater risk than copper if done properly. What I'm interested in is what is "done properly" and have there been tests done on such "proper" wiring methods to prove that they do in fact pose no increased fire hazard?
So in other words, what I'm looking for is published (on paper, internet, etc.) information from reputable sources that would refute the claims made by the information that I've already read making aluminum out to be a fire hazard. A lot of the information I've read so far can be found at
I have been installing AL for more than 30 years. There is nothing wrong with the wire. The problems come from the installers and the terminations. If properly terminated there will be no more problems with AL than copper. I do not know of any utilities that use copper any more. All of the long lines and distribution lines in the West are primarily AL. If they were not some maroon would steal them. Which has happened in the old days, 1960-70's. All of that wire was replaced with AL.
Your home and mine (also built in 1971) have lasted this long. Chances are they will last a lot more. This is my 3 home of this vintage. Do you know anyone with a 1000 volt meggar? You will need to unplug EVERYTHING for the test. The meggar can tell you if there is an insulation problem and to a point loose connections.
Most of the published articles are done by fire departments and the copper association. Unfortunately the fire department only gets to visit when there is a problem.
Ideal makes a wire nut for AL-CU connections. About $2 ea at the box stores. Devices should be listed AL-CU and they are harder and harder to find.
I live in the midwest and AL wire is used on most new transmission lines I see. How about homes - I thought AL wiring in homes no longer was approved? When I lived in the south a bunch of "modular homes" factory built with AL wiring burned - had everybody looking at their wires.
The problem with AL wiring in homes is at the connections ... transmission lines would obvioulsy have very different connection systems in place compared to your average home. There is for example an approved and tested method of making aluminum wire connections to copper wire using an COPALUM tool. Chances are something similar, but on a bigger scale, is done with transmission lines ... however, comparing transmission lines to home wiring, doesn't really prove much since they are such different systems.
You made some good points on the differences between Al and Cu. Just to further clarify, Cu has both and electrical and thermal conductivity that is nearly 65% greater than that of Al. Not only does conduct electrons better, Cu ability to dissipate heat is far greater than that of aluminum. Cu does oxide at room temperature, but rather slowly. Further, Cu oxide (CuO) does not form a tough coherent film. On the other hand Al is one of the most powerful reducing agents known to man (check out the thermite reaction
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Any aluminum surface oxidizes almost immediately and as the oxide layer grows conductivity drops exponentially (this is why aluminum is so difficult to solder). Both metals are prone to work hardening (if bend it repeatedly it gets stiffer and then breaks). On the down size Cu is more expensive and 3 times more dense than Al, but weight matters little in a home. If sized properly to compensate for current load as well the use of dielectric greases, Al is a fine choice. On the other hand if done poorly, the joints could easily heat up as the aluminum oxide grows and potentially cause a fire. Without a doubt aluminum makes an excellent choice for high tension power lines, however, in the home I would prefer copper. This doesnt make aluminum unsafe, its just a preference.
What really happened was copper went through the roof in price so people started using AL and AL clad copper wire. Let us not go into the copper clad stuff. During the time that copper was high and the less than craftsmen were using the AL romex there were a lot of problems. One contractor where I lived lost his electrical license because of fires. He even burned his own mothers home down.
The problem lies in the craftsman pulling the wire and doing the terminations. Using the proper devices, ( switches and recpts ) is also a biggie. I know of lots of "electrical workers" that stabbed the AL wire into the back of the devices. Even though the device instructions said not to with AL wire. ( use the side screws ).
Larger AL wire is connected using hydraulic press tools. There are even AL to copper connectors made. I have never seen a hydraulic pressed termination go bad not in 30 years. Providing it was done correctly in the beginning.
Today there is a different alloy used and different insulation. New homes today have circuits above 30 amp AL is still used. ( general guideline ).
You can spend the money for copper. I doubt that you will see a penny when selling the home. No one cares what is in the walls. People accept plastic flexible water pipes ( general term ) all of the time now days. Some new home builders do not even offer to put in copper water pipes.
No offense intended. Sanding a bare new conductor went out 20 years ago along with tape built up stress cones. If there is oxidation on the wire when terminating after you cut back the insulation, testing is in order in my mind. There could be more issues involved.
Anti oxidant is a good thought. The local utility and I have used axle grease in a pinch. I learned that from them not the other way around. All your trying to do is prevent oxidation after the connection is made. I will and do use anti oxidant on terminations and splices.
There were switches and outlets that when the side screws were used no anti ox was needed. I have not tried to buy them in ages cause I do not do that kind of work any more. I do know that going to the box stores and trying to find an device for AL is going to be next to impossible. At least in the box stores I have been in lately.
Pigtailing out in copper is/was an acceptable method. Ask some pros in you local area to see what they do.
1971 was a particularly bad year. Aluminum wiring is just fine for feeders, service entrance conductors, and other large capacity circuits (generally, 30A and larger). The biggest problem was with 15A devices sold until about 1972 -- it was impossible to make a proper connection with aluminum wire that would not oxidize and eventually fail. Aluminum wiring to an electric stove, clothes drier, central A/C, water heater, or subpanel is probably OK (the terminals will be listed something like "CU-AL" or "AL7CU")
There are new (expensive) replacement devices that are listed for use with copper or aluminum wire that are marked "CO-ALR" (if I recall correctly) that can be used on aluminum 15A branch circuits without needing copper or copper-clad pigtails.
I believe the CO-ALR devices is a better retrofit than adding a copper pigtail unless you get special crimp connectors made especially for joining small aluminum-to-copper conductors.
I would not live in a house with 15A aluminum branch circuits unless
*every* connection had been inspected and upgraded as necessary. I would rip the "easy" ones out completely and replace with copper.
Best regards, Bob (not an electrician, just opinionated :-)
In addition to using properly labeled fixtures, the main thing you need to use is an antioxidant on the aluminum where it is joined to any other wire or terminal. The AL wire should also be scraped or sanded to remove oxidation before making a connection. (I think this is in the NEC)
The failure mode of AL wiring is a build up of aluminum oxide (equivalent of rust) inside the terminal contacts. This causes a rise in resistance of the junction which will experience heating when current is flowed through it. With enough resistance and current, sufficient heat can build up to ignite nearby sources.
Placing a paste like anti oxidant on freshly stripped and sanded AL wire will prevent the oxidation from occurring in the first place and ensure a low resistance connection.
The terminals on CU/AL rated fixtures are more thermally compatible with the AL so that it does not come loose (due to thermal expansion) which is another cause for increased resistance and eventually heat.
With lamps turned on or something plugged into a receptacle, if you feel any warmth coming from behind the wall plate, you should do something about those immediately.
The AL metal its a superior conductor, and it is durable and easy to work and install.
I understand that oxidation of the Al metal surfaces at the connections are the main problem. AL oxide has a high dielectric strength, meaning that it is poor conductor of electricity. In a simple connection, and over the span of a few years, the AL oxide forms on the exposed surfaces. The AL to AL contact area gets smaller. The electrical resistance at the contact area is increased. Heating is a function of current and resistance. The contact area get hot, and if the resistance is high enough slight melting could occur. the contact area or the cross sectional area of the wires may get smaller, and the resistance, and hence the heating, increases. The connection melts down and fails.
CU oxide does not have as high a dielectric strength, and while the same process can occur the amount of heat produced may be less.
I read that a coating can be applied to the finished connection of AL-AL or AL-CU metals that prevents oxidation over a long period of time. That, I think, is used in marine or shore environments. What is that coating? Crimp type clamped wire connections may provide great enough contact surface area and no access to O2 that the contact keeps a very low resistance that is lower than the wire itself for the life of the connection.
AL wiring is low in cost, and is an efficient conductor. If oxidation is allowed to occur in either AL or CU connections, especially those that are not made with a sufficient surface contact area, and that are not tight, heating and sputtering can occur.
I had a window air conditioning unit that was connected to two
3-wire extension cables. The copper contacts of the power cable had green oxidation, and after the power went on the cable outer ends were warm. Later in the day the cable to cable connection exploded in a flash of light and smoke. The circuit breaker opened. I am highly suspicious of cheap power extension cables that have the wires and metal bits molded into a low melting temperature rubbery plastic cable end with no other wire separators or electrical insulation. Corrosion free connectors may save electricity.
AL is a poorer conductor. Simple physics. Look it up. That's why it has to be a guage larger than copper for the same ampacity.
It's reasonably durable, but not only is it stiffer (both because it is stiffer than copper to begin with, and because it has to be a gauge larger for the ampacity), it's more brittle. Hence, more difficult to work with than copper for the same ampacity, and more likely to get work-hardened and crack if not handled properly.
And finally, due to its dialectric and "cold creep" properties, under identical conditions, it will deteriorate faster than copper.
As such, aluminum is far more sensitive to sloppy workmanship, codes _require_ anti-oxidant grease (not necessary for copper), and most municipalities have banned the use of aluminum in residential wiring.
Certainly, for power distribution (60A and up), its price advantage is enormous, so you do what you need to to make it safe.
But in general residential wiring, these days its a very bad idea. And illegal in many places.
I've been working with wiring for a very long time. The only connections I've ever seen burn out (aside from ones physically damaged, exposed to water, or due to unbelievably bad workmanship) have been aluminum.
It all depends on the real estate market in your area. I know in my area, the wiring won't make much difference with the market we have right now ... even knob and tube wired houses sell. I'm willing to accept the fact that whatever money I spend on the wiring will never be recovered. I want to fix things for safety sake mainly.
Well I have seen outlets in older manufactured homes which stopped working or would spark inside if you turned on something plugged into the outlet.
Turns out there was aluminum wiring connected to the outlets which had oxidized.
If I had aluminum wiring, I would want to treat it like I do my car battery terminals - inspect each and every connection periodically and clean/apply goop up the connections if necessary.
I would sleep better at night if I replaced it all with copper though...
OK, what I don't understand then is why a testing agency is able to proof that for example a wirenut approved for aluminum can fail when installed properly and under normal conditions. If this wire nut is part of the "proper" methods involved in installing aluminum wiring, and when done properly is supposed to be completely safe, then why are they able to prove that it's unsafe?
I'm specifically refering to the information on the Ideal wire nuts presented here
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(about half way down the page).
Thanks, Harry
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Chris Lewis Aug 10, 9:54 am
According to zxcvbob :
If it was done _correctly_, Al wiring has always been safe. Cu/AL rated connectors/devices have been around as long as Al wire has. The problem mostly being craftsmen who didn't follow the rules, and Al being less forgiving of poor workmanship.
BTW: "CU-AL" designations are largely obsolete, electrical standards now primarily call for CO-ALR. Considered better than CU-AL, but CU-AL
is still okay
Canada has always accepted CO-ALR wirenuts alone (without anti-oxidant grease) for routine 15A circuits. But the wirenuts are becoming harder
and harder to find and are quite expensive (compared to ordinary ones).
[Larger Al connections require appropriatedly rated terminal connectors/ clamp devices, and anti-oxidant grease like in the US.]
US code appears to have been fluctuating rather a lot in regards to copper pigtailing. At one point at least, the ONLY legal way to pigtail Al to copper was with a very specialized crimp connector (~$5-10 _each_) and an expensive crimping tool (>$500). IIRC, the "system" was manufactured by "AMP", and they wouldn't sell you the stuff unless you took a course on how to use it.
-- Chris Lewis, Una confibula non set est It's not just anyone who gets a Starship Cruiser class named after them.
OK, I think Arnold summarized things pretty well so far:
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What you're going to find out is that everybody agrees that Al done improperly is a high risk. Then find that there is considerable disagreement over whether Al "done properly" represents enough _more_ of a risk over
copper to be concerned about. So you're not going to find exactly what you want in terms of "proof".
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So in other words, AL wiring can be made safer, but even done properly it's very possible that it will never be as safe as copper .... with the possible exception of using the COPALUM tool ... no one seems to have ever been able to show that a connection made with the COPALUM tool can fail under normal conditions ... which would coincide with what SQLit said about hydrolic pressed connections never failing, since the COPALUM is basically that, a hydrolic crimping tool.
I bought a house that someone had wired the basement with aluminum. Only one room was sheetrocked, so I left that part of the wiring in. The rest I removed and trashed.
A few years later, the overhead light stopped working in that room. It was necessary to cut through the drywall and rip out ALL of the aluminum wiring. The connections were corroded and probably very unsafe. We replaced it with copper. The lights work again. The lights have always worked in the rooms wired with copper.
I don't know if this is an aluminum thing or not, but many electric service connections are aluminum. These done properly are applied with aluminum wire goop and then the connections are torqued to main panel manufacturer's specifications.
Yet it is not uncommon for these connections to become loose and need to be re-torqued.
The question is: Does this occur more so with aluminum main service wiring than with copper main service wiring?
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