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 www.inspect-ny.com/aluminum.htm
Thanks for the input,
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
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
Thanks for the info on the meggar.
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.
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
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
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
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.
Biggest problem was probably the switches and receptacles (although
backstabing them would be a real bad idea). After problems developed, UL
removed listing on wire and devices in 7-1971. In 9-1971 they started
listing devices which are marked CO/ALR. I havn't heard of problems with
these devices. If I was using them, I would probably use some anti-oxide
paste on the aluminum wire.
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
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...
Thank you for the reply. I like your point about the fact that a lot
of the published articles are probably done by fire departments, etc.
But taking the example of the Ideal wire nut ... who do I believe. The
information presented here:
Or individuals like yourself and others who've never had issues with
these connectors in their own homes? Hence my dilema ...
Also, as a side point ... what do you consider "properly terminated"?
Using AL approved outlets and switches, pigtailing, etc.?
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
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
No offense intended.
Sanding a bare new conductor went out 20 years ago along with tape built up
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
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.
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.
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
http://en.wikipedia.org/wiki/Thermite). 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
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.
Chris Lewis, Una confibula non set est
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