Al vs Cu.......are they equal?????? Which do you prefer and why?????

Besoeker

Senior Member
Location
UK
Perhaps a different perspective from across the pond.......
For LV installations Al is rarely used. I won't say never but, in about 50 years in the field, I haven't seen one using Al.
Of course we have different installation methods. Conduit isn't used very much. Industrially, a short run from trunking to a light switch is the most I have seen in the last couple of decades. And that was white PVC 15mm. It was more common when I started and that was usually the black stuff - those that were used to it were calle black puding benders.

Mostly, we use steel wire armoured with copper conductors. Why not Al? I don't know.

The only installations I've seen in recent years has been on the output of high current rectifiers - tens of kA.
We designed and manufactured the rectifiers. All of that was copper. Even the heatsinks.

The installation was done by others. Cost and weight were possibly factors in the choice of material given that the runs were overhead...........
 

Sahib

Senior Member
Location
India
The reliability/safety of Al wiring depends on its correct installation. But take into account Murphy's law: If anything can, it will. So if you are not very confident about Al wiring, use Cu wiring.
 

Besoeker

Senior Member
Location
UK
The reliability/safety of Al wiring depends on its correct installation. But take into account Murphy's law: If anything can, it will. So if you are not very confident about Al wiring, use Cu wiring.
How often have you used one compared to the other?
 

Sahib

Senior Member
Location
India
How often have you used one compared to the other?
In the nineties when I joined, both staff quarters and telephones exchanges were wired with Al wiring. Later the ban on using Cu wiring was lifted and we began to use exclusively Cu wiring for small diameter wires and Al wiring for others.
 

iwire

Moderator
Staff member
Location
Massachusetts
Just a small point, this thread has been about larger conductors

Aluminum is not available here in sizes smaller than 8 AWG
 

Besoeker

Senior Member
Location
UK
In the nineties when I joined, both staff quarters and telephones exchanges were wired with Al wiring. Later the ban on using Cu wiring was lifted and we began to use exclusively Cu wiring for small diameter wires and Al wiring for others.
Which did you prefer?
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
I suppose there's a reason for that?
I would suspect that aluminum has a lower ductile strength than copper, so pulling smaller wires through dies causes more breakage in aluminum than in copper. But that is speculation on my part.

I use copper for short runs and/or small gauge wiring where the cost differential is not that much, but for long runs of large gauge wiring, I spec aluminum whenever I can.
 

user 100

Senior Member
Location
texas
I suppose there's a reason for that?
Yep- In residential at least, smaller gauge aluminum (esp solid) was pretty much mothballed in the states after the al (old pre 8000 series alloy) res fire reports in the '70s.

Considering the cost of copper, there have been discussions about possibility of a new improved silver nm hitting the market at some point, but barring something incredibly drastic, I don't see it happening anytime soon, if ever, because of the stigma surrounding the old al nm.

As for the money saving aspect, al obviously looks more attractive when used in larger sizes, not so much in smaller sizes.
 
Last edited:

iwire

Moderator
Staff member
Location
Massachusetts
I suppose there's a reason for that?
In the mid sixties early 70s a lot of homes where wired with 12 and 10 AWG solid aluminum branch circuits. This was a disaster, the alloy was not right, the devices where not designed for aluminum. It was so well publicized that no one wants it and the manufactures who had been sued don't seem interested in making it. It is still code compliant.

However 8 AWG and larger is stranded, the alloy is different and the devices are now designed to work with it.

Millions of homes use 6 AWG AL for their electric range / stove. Millions of home services are installed using AL. I have not heard that these and larger sizes where ever problematic.
 

dfmischler

Senior Member
Location
Western NY
I would suspect that aluminum has a lower ductile strength than copper, so pulling smaller wires through dies causes more breakage in aluminum than in copper.
I just want to point out that there is a lot of copper-clad aluminum network wiring coming in from China (and being purchased by people who believe the lie that it complies with the appropriate standards). Somebody is able to manufacture small gauge aluminum wire on a large scale, although maybe not with great quality.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
The reliability/safety of Al wiring depends on its correct installation. But take into account Murphy's law: If anything can, it will. So if you are not very confident about Al wiring, use Cu wiring.
the safety of all wiring depends on it being installed correctly.
 

JFletcher

Senior Member
Location
Williamsburg, VA
In the mid sixties early 70s a lot of homes where wired with 12 and 10 AWG solid aluminum branch circuits. This was a disaster, the alloy was not right, the devices where not designed for aluminum. It was so well publicized that no one wants it and the manufactures who had been sued don't seem interested in making it. It is still code compliant.

However 8 AWG and larger is stranded, the alloy is different and the devices are now designed to work with it.

Millions of homes use 6 AWG AL for their electric range / stove. Millions of home services are installed using AL. I have not heard that these and larger sizes where ever problematic.
Well said. The other main problem with the 10 and 12 is that it doesnt take well to being tightly packed into those older 12-16ci boxes, especially if box fill is on the high side, and tends to break if disturbed. Alumiconns seem to lay flatter and fit better in those boxes than the purple wire nuts.

Devices are still mostly made for Cu only; copper would probably have to hit a sustained $15/lb before we'd see all devices made for Al.

Ive seen plenty of hosed up 10/12 Al, but never with the 8 and 6 stranded for dryers, ovens, and ranges.
 

user 100

Senior Member
Location
texas
Well said. The other main problem with the 10 and 12 is that it doesnt take well to being tightly packed into those older 12-16ci boxes, especially if box fill is on the high side, and tends to break if disturbed. Alumiconns seem to lay flatter and fit better in those boxes than the purple wire nuts.

Devices are still mostly made for Cu only; copper would probably have to hit a sustained $15/lb before we'd see all devices made for Al.
CO/ALR devices will work- the trick is to terminate them correctly and if you ever happen to run across any device marked "CU/AL," junk it- I believe that those devices were never actually tested to perform w/ aluminum. Still the alumiconns w/copper tail to like device is, imo, the way to go. Of course alumiconns can be and have been screwed up too, by overtorquing.:)
 

dionysius

Senior Member
Location
WA
......the trick is to terminate them correctly...... :)
Any specific examples of poor terminations ??? It seems any reasonable electrician with IQ > 90 would have to try to not do the job properly. Strip without nicking (also applies to Cu), correct strip length (also applies to Cu); correct torque (also applies to Cu); DeOx is optional; what have I left out???????
 

JFletcher

Senior Member
Location
Williamsburg, VA
Any specific examples of poor terminations ??? It seems any reasonable electrician with IQ > 90 would have to try to not do the job properly. Strip without nicking (also applies to Cu), correct strip length (also applies to Cu); correct torque (also applies to Cu); DeOx is optional; what have I left out???????
Straightening out a 'candy cane' from around a screw, then rebending it for a new device; thats practically asking for broken 10/12ga Al wire. Mashing wires back in the box can do the same.

I often see strip length too short, resulting in wire wrapped 1/2 to 3/4ths around a screw, or insulation caught under the screw head, as well as wires with no twist under a wire nut. Imo wires should not spring apart or separate if a wire nut is removed, tho those problems arent unique to Al.
 

user 100

Senior Member
Location
texas
Any specific examples of poor terminations ??? It seems any reasonable electrician with IQ > 90 would have to try to not do the job properly. Strip without nicking (also applies to Cu), correct strip length (also applies to Cu); correct torque (also applies to Cu); DeOx is optional; what have I left out???????
The biggest one imo is torque. Have found a few of those co/alr devices terminated to old al nm that have failed b/c of overtorquing- with that old crap going too tight is just as bad as leaving it loose. The thing a long time ago was that since the old al creeped substantially undr the steel screws of standard and al/cu devices, that it was best to make everything "xtra" tight:happyno:, and that persistent mindset, along w/ the fact many are solely used to copper and it's tolerances leads to issues- you're trying to secure the wire, not flatten it and those terminations on co/alr don't need to be that friggin' tight!!!. This is one the main reasons I find the alumiconn pigtail appealing: if somebody else who is ignorant replaces the receptacle, at least it reduces the possibility of running into als sensitive torque issue, terminate wrong on a standard device and eventually start a fire.

Also the problem mentioned by jfletcher above with the old al when tucked into box- excess needs to be trimmed and whatver is left needs to be looped/laid in the back of box, not jammed in there w/ sharp bends.

As for lugs, same thing (screw crushing strands) along with bad seating (crooked and pinched) and/ not enough conductor strip, don't believe I have seen one fail b/c of lack of nolox- (not saying it isn't ever needed, just that it may not be needed as often as some think;)).
 
Last edited:

Fulthrotl

~~Please excuse the mess. Sig under construction~~
CO/ALR devices will work- the trick is to terminate them correctly and if you ever happen to run across any device marked "CU/AL," junk it- I believe that those devices were never actually tested to perform w/ aluminum. Still the alumiconns w/copper tail to like device is, imo, the way to go. Of course alumiconns can be and have been screwed up too, by overtorquing.:)
for residential aluminum installations, where AL rightly deserved it's black eye,
there are only a couple approved methods of fixing the problem. this one seems
to be the best, and least used:

http://www.te.com/usa-en/products/application-tooling/hand-tools/power-assist-tools/intersection/copalum.html
 
Top