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

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Fulthrotl

~Autocorrect is My Worst Enema.~
I meant unfounded as in excessive concern. I can definitely see where they would be worried esp w/ terminations or anything exposed in that type of environment- apparently for cost sake, the bean counters realized there are effective ways of accommodating this less expensive conductor- specs are everything until somebody makes an informed decision and decides they won't pay for them.

As for swaged vs. sc, I think a lot of it has to do w/ the initial installation- a huge problem w/ al is improper torquing as Peter d mentioned above- often the connection is doomed from day one and will eventually fail b/c someone decided to "flatten" instead of merely terminate.

that's the thing about swaged terminations. it's as close to a manufactured device as
you can get in the field. you're using a die made for that specific application, and
applying 12 tons of pressure to form it into one piece. you can also exclude moisture
with heat shrink, so it won't oxidize and corrode.

of course set screw lugs are listed AL9CU, and will work fine, yada.... however, i've
never seen a hypressed lug fail in the lug to cable join, and i can't say that for
setscrew connections.

to answer the other question, the reason i use pin terminations, is that my inspector
had issues with changing out the factory lugs on the panel. so, i used pins, and torqued
them with a torque wrench.
 

iwire

Moderator
Staff member
Location
Massachusetts
I was just reading up on some terminations and they all show tell you to wire brush or rough sand the wire end before crimping or terminating or putting no lox on it.

The directions on every can of anti ox paste tell you to do that.

I doubt many are.
 

Tony S

Senior Member
that's the thing about swaged terminations. it's as close to a manufactured device as
you can get in the field. you're using a die made for that specific application, and
applying 12 tons of pressure to form it into one piece. you can also exclude moisture
with heat shrink, so it won't oxidize and corrode.

As an apprentice I cut a 185mm² (somewhere between 3/0-4/0) aluminum compression termination in half, polished it and applied a crack detector solution. Under the microscope only the centre 15% showed any voids. Correct dies, pressure and terminations does as you say, “form it into one piece”. Heat shrink is the icing on the cake.
 

iwire

Moderator
Staff member
Location
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Right. But then again, the wire nec and wire manufacturers don't require us to use deox in the first place.

:thumbsup:

No argument from me and while I have some deox in the truck I rarely use it as most of my AL work is for temp stuff so all it does is add mess to the work.
 

Fulthrotl

~Autocorrect is My Worst Enema.~
Right. But then again, the wire nec and wire manufacturers don't require us to use deox in the first place.

well, common sense says if i cut the end of the wire, and skin it, that conductor
has been exposed to the air for 5 minutes, so it's probably not oxidized all that
much. then, the lug has noalox pre squirted into the lug, and when you squeeze
it, it comes out and makes a nice mess. do i wire brush the cable before crimping?
no.

now, bare aluminum transmission line would be another thing altogether.
normally, you tape back behind the crimp area with friction tape, and put
a wire brush in a battery drill, and go at it a bit, especially if the stuff has
been sitting on a spool in a utility yard for five years......
 
I recall reading about the oxidation issue (it was a reputable source, don't remember who though) and they stated that the oxidation layer is quite thin and fragile and gets all broken up when tightening the lug so removing it is not necessary. Now, like FT said, if I did have a piece that had been laying around exposed for a long time and had those whitish spots all over, I would wire brush it.
 

RobertKLR

Member
Location
Texas
And not all electricians are knowledgeable about how to install al.:)

As said above the smaller solid sizes of the poorly terminated old stuff is what primarily gave/gives you issues. A lot of the stuff about al is overblown - it's not unusual to see an old al range ct thats trouble free. Even most bare transmission lines contain a high aluminum content and they plug along decade after decade.

True. I have almost zero experience with aluminum wiring. I can count the jobs using aluminum on one finger. This thread has been very educational for me on the topic.
 

iwire

Moderator
Staff member
Location
Massachusetts
Considering the material and extra labor to install larger conduit and AL wire to reach the same ampacity, is the delta really 4 times plus?

This white paper mentions up to six times per amp.

https://w3.siemens.com/powerdistrib...Center-Whitepaper-Aluminium-versus-Copper.pdf

From page 3
The advantages of Aluminum over Copper for these
applications are obvious:
·
Significantly lower material costs (up to 6 times
lower than Copper per Ampere),
·
About half the weight of Copper per Ampere.

As far as larger conduits, not very often, we tend to run bigger than needed anyway.
 

dionysius

Senior Member
Location
WA
Is there a bottom line??????

Is there a bottom line??????

Based on what I read in this thread so far the verdict is clear. The product being used today is not just Al. It is a much more perfected and engineered alloy as are the alloys that make up the connectors. The "creep" issue has been neutralized.

Please do everyone a favor and challenge your prejudices and biases. Consider Al as well as Cu in all future jobs where appropriate and do not be afraid of setscrew lugs. Use of NoOx is optional in freshly stripped terminations. Do be diligent about torquing to specs.

Never forget that Cu also forms oxides readily.
 

user 100

Senior Member
Location
texas
Based on what I read in this thread so far the verdict is clear. The product being used today is not just Al. It is a much more perfected and engineered alloy as are the alloys that make up the connectors. The "creep" issue has been neutralized.

Please do everyone a favor and challenge your prejudices and biases. Consider Al as well as Cu in all future jobs where appropriate and do not be afraid of setscrew lugs. Use of NoOx is optional in freshly stripped terminations. Do be diligent about torquing to specs.
specyive
Never forget that Cu also forms oxides readily.

The way I understand it, copper oxide is still a pretty good conductor, and you will see ancient cu terminations with a coating of patina that are non problematic. Al oxide otoh is an awful conductor.

Glad too you got what you feel is some good perspective.:)
 

ron

Senior Member
As far as larger conduits, not very often, we tend to run bigger than needed anyway.
With AL needing to be at least 68% larger cross sectional area as compared to CU for similar ampacity, the bigger conduit would have to be even bigger.

I have had AL on projects (successfully), but I'm not sure if a good apples to apples comparison gets done each time from a total cost of ownership.
 

Fitzdrew516

Senior Member
Location
Cincinnati, OH
As someone who's specs are copper only I will tell you that some of you are making the right assumptions as to why it is spec'd. I cannot be on site and watch every connection being made. Since aluminum is installed slightly differently it is safer from a design perspective to spec the easier of the two products. Really what it comes back to is - If something goes wrong who is the owner going to blame? That is almost always the engineer regardless of who is really at fault. Even if the owner agrees that something wasn't your fault it's still hard to get repeat business if the screw up was big enough.

Another reason I can think of (not necessarily a good reason), but since most firms always spec copper then all of their internal infrastructure, calculators, charts, etc. is all based on copper. If you change to aluminum then they have to spend more time designing because they don't have the standard tools available to them. Again, not a good reason at all which is why whenever I create a new design tool I always make it for copper and aluminum.

I would happily spec aluminum if I knew it were going to be installed correctly, the reality is that I don't know that. I understand it's a slippery slope and honestly I would be okay with trying to spec aluminum more often, but often there is also the uneasiness that is still in company higher ups that makes the spec remain copper only.
If the contractor contacts me directly and they want to take the design for certain feeds into their hands I am often okay with them changing to Al once we go over and discuss that they will be installing everything how it should be done. I make it clear to the owner that anything changed with the design is the contractor's responsibility at that point. I have done that in the past and have no issue with it on a case by case basis.
 

dionysius

Senior Member
Location
WA
I would happily spec aluminum if I knew it were going to be installed correctly, the reality is that I don't know that. I understand it's a slippery slope and honestly I would be okay with trying to spec aluminum more often, but often there is also the uneasiness that is still in company higher ups that makes the spec remain copper only.

Again this is all about clinging to the perception of comfort. Cu is now as much as 10 times more expensive than Al. Any competent installer can install Al. Put in another way if he/she screws up an Al installation then with equal probability he/she will screw up a Cu installation. Re the company higher ups.....if they were aware of the money to be saved trust me they would be all over Al.
 

ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min from the winged horses.
Occupation
Licensed Electrician
I would happily spec aluminum if I knew it were going to be installed correctly, the reality is that I don't know that..
It's not any harder to install aluminium than copper. Again, almost 100% of our power grid is aluminium and that stuff is installed by linemen. Ever hung out with a bunch of linemen? Great guys, but they aren't a nuanced bunch.

....Any competent installer can install Al. Put in another way if he/she screws up an Al installation then with equal probability he/she will screw up a Cu installation....
Bingo. Yup. Right on.
 

Fulthrotl

~Autocorrect is My Worst Enema.~
With AL needing to be at least 68% larger cross sectional area as compared to CU for similar ampacity, the bigger conduit would have to be even bigger.

I have had AL on projects (successfully), but I'm not sure if a good apples to apples comparison gets done each time from a total cost of ownership.


500 mcm thwn-2 copper is 430 amps
750 mcm thwn-2 aluminum is 435 amps.

it's a 50% increase.

three 750 aluminum and 250 aluminum ground in 4" grc is 35.7% fill
three 500 copper and 250 copper ground in 4" is 19.6% fill

you can put the copper in 3", but i'm guessing if you had a 400' run,
you'd use 4".......

so, just for grins, let's assume both runs are 4"

copper = $12,316
aluminum = $3,644

29% of the cost... year before last, when i bought large aluminum, it was 22%.
assuming swaged lugs.... i can't see the justification for large copper feeders.

the delta on 4" versus 3" emt is about $1,000 for a 400' run.
 
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