# Aluminum service conductors



## jeepman (Jan 2, 2013)

We use aluminum in my area from the service to the main in the panel on resi. Only of course


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## Hotlegs (Oct 9, 2011)

jeepman said:


> We use aluminum in my area from the service to the main in the panel on resi. Only of course


Will they allow this on commercial in your area? I did an all aluminum 600 amp service in Arlington , TX that was allowed.


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## electricmanscott (Feb 11, 2010)

jeepman said:


> We use aluminum in my area from the service to the main in the panel *on resi. Only of course*


Is there different electricity in resi vs commercial? :confused1:

I haven't used cu conductors for a service in ages. This has been argued to death but it's no biggie either way.


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## jeepman (Jan 2, 2013)

Hotlegs said:


> Will they allow this on commercial in your area? I did an all aluminum 600 amp service in Arlington , TX that was allowed.


No only resi


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## jeepman (Jan 2, 2013)

When I get to my lap top tonight I will post some pics


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## Bulldog (Jan 28, 2009)

It depends on your area. Some areas require the service to be designed by a PE. If the PE requires Cu conductors, than you could ask if could be changed to Al conductors. The change has to be in writing.


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## B4T (Feb 10, 2009)

Some use AL on the line side of meter pan since they are being connected to AL service drop from PoCo....

Also using CU. on the load side of MP into panel means the HI won't write down AL wire on his inspection report when taking panel cover off...

AL wire is a red flag here on Long Island... LOTS of high profile house fires from it and people don't forget those kind of things.. :no::no:


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## Cletis (Aug 20, 2010)

B4T said:


> Some use AL on the line side of meter pan since they are being connected to AL service drop from PoCo....
> 
> Also using CU. on the load side of MP into panel means the HI won't write down AL wire on his inspection report when taking panel cover off...
> 
> AL wire is a red flag here on Long Island... LOTS of high profile house fires from it and people don't forget those kind of things.. :no::no:


The fire was from the installers NOT the aluminum wire !


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## B4T (Feb 10, 2009)

Cletis said:


> The fire was from the installers NOT the aluminum wire !


You are wrong.. it was a combination of both...

There were installers speed wiring the AL or not doing a very good job of using the screws...

This goes back to the houses wired in late 60's and 70's when CU was scarce because of the Vietnam War..


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## aftershockews (Dec 22, 2012)

We are allowed to use Al on services here, although my boss does not like to do it. And unless local AHJ has changed, we are/were allowed to use AL on heavy circuits such as dryer, stove, heating, ect.
We have alot of copper theft on commercial buildings. If the conduit will allow for fill, I will use AL to replace. Once had a job where the thieves cut the lock on the transformer and stole the coper from it to the trough where the service equipment is. I replaced in AL.


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## Cletis (Aug 20, 2010)

Can someone Pleazzzzz forward this to the Long Island Building Dept ?? 

http://www.iaei.org/magazine/2006/01/aluminum-building-wire-installation-and-terminations/

They have 40 yrs to catch up on


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## Cletis (Aug 20, 2010)

Cliff Notes by IAEI

Aluminum building wire today is *at least as safe and reliable as copper* building wire. Listed connectors are evaluated and manufactured specifically for aluminum connections. *AA-8000 conductors now have over 30 years of field installation examples* proving their reliability and have been *recognized* in the *NEC for nearly 20 years*.

AA-8000 series aluminum alloy conductors provide a safe and reliable method of designing and installing electrical systems. They are available as single conductors, in cable assemblies such as MC cable and SE cable, and a variety of other configurations to meet the needs of different installations.


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## electricmanscott (Feb 11, 2010)

Cletis said:


> The fire was from the installers NOT the aluminum wire !





B4T said:


> You are wrong.. it was a combination of both...
> 
> *There were installers speed wiring the AL or not doing a very good job of using the screws...
> *
> This goes back to the houses wired in late 60's and 70's when CU was scarce because of the Vietnam War..


So how was he wrong??


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## nrp3 (Jan 24, 2009)

Aluminum all day long, in the mast, SE up the side of the house, in the ground. Utility gives us the socket and then they show up and put up the SE from the socket up.


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## Elephante (Nov 16, 2011)

Good job cletis. He agreed without even knowing it.


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## B4T (Feb 10, 2009)

Cletis said:


> The fire was from the installers NOT the aluminum wire !


How can you say that.. :blink::blink:

Both CU and AL conductors were installed on receptacles using the exact same wiring methods....

The Al installation caught fire and the CU installation performed without fire... flame or smoke...

So it doesn't take a rocket scientist to see the problem was the AL conductor itself..


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## Chris1971 (Dec 27, 2010)

B4T said:


> How can you say that.. :blink::blink:
> 
> Both CU and AL conductors were installed on receptacles using the exact same wiring methods....
> 
> ...


It all comes down to improper installation.


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## HARRY304E (Sep 15, 2010)

Chris1971 said:


> It all comes down to improper installation.


Yes ,but more like careless installation..


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## BBQ (Nov 16, 2010)

B4T said:


> You are wrong.. it was a combination of both...
> 
> There were installers speed wiring the AL or not doing a very good job of using the screws...
> 
> This goes back to the houses wired in late 60's and 70's when CU was scarce because of the Vietnam War..


So why aren't the hundreds of thousands of homes away from LI with aluminum service conductors burning down?

There is no real reason not to use AL other than ignorance and fear.


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## HARRY304E (Sep 15, 2010)

BBQ said:


> So why aren't the hundreds of thousands of homes away from LI with aluminum service conductors burning down?
> 
> There is no real reason not to use AL other than ignorance and fear.


Money changes minds.


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## Peewee0413 (Oct 18, 2012)

BBQ said:


> So why aren't the hundreds of thousands of homes away from LI with aluminum service conductors burning down?
> 
> There is no real reason not to use AL other than ignorance and fear.


Aluminum is not always safe. If not installed properly(loose connections), aluminum oxide is not conductive. Which will cause the fires ..aluminum can be safe. Just not as safe as copper.


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## nrp3 (Jan 24, 2009)

Loose copper connections aren't exactly great either.


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## Bulldog (Jan 28, 2009)

B4T said:


> How can you say that.. :blink::blink:
> 
> Both CU and AL conductors were installed on receptacles using the exact same wiring methods....
> 
> ...


It was the poor design and allowing the use of Al wire on brass terminals. Both have a different coefficient expansion factor. Which causes the device to start arcing. Brass screws will expand faster than Al wire. Even if you connected the wire on the brass terminal and used a inch pound screwdiver at the correct setting the wire would after time come loose to to unequal expansion. Al terminal on devices should have been required from the beginning.


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## B4T (Feb 10, 2009)

BBQ said:


> So why aren't the hundreds of thousands of homes away from LI with aluminum service conductors burning down?
> 
> There is no real reason not to use AL other than ignorance and fear.


Because when they had high profile fires and people died the press was all over it...

Many houses were pigtailed.. but using standard wire nuts... they didn't know any better..


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## Chris1971 (Dec 27, 2010)

B4T said:


> Because when they had high profile fires and people died the press was all over it...
> 
> Many houses were pigtailed.. but using standard wire nuts... they didn't know any better..


It all boils down to improper installation.


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## Dennis Alwon (May 9, 2009)

When aluminum wire first came to the NEC was there instructions to use noalox or was that an after thought when the realized the problems with aluminum. I realize that is not an issue now but it may not be totally an install error if those facts were not known.


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## Cletis (Aug 20, 2010)

I thought this thread was about service entrance cable. Now that I know old aluminum branch cir. that's a different thing. Obviously, someone didn't research the brittleness of old single strand aluminum nm...ooopss

Since you can't run aluminum "Generally" to branch circuits and they corrected brittleness problem what's the problem with the new aluminum ?? Superstition? Mis-information? Lack of Knowledge? or all the above and more ? 

Did they put the alum on brass screws where the fire happened? dummies


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## Dennis Alwon (May 9, 2009)

The new aluminum has a different alloy then the old so the expansion and contraction issues of the old wire is not present with the new stuff.


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## BBQ (Nov 16, 2010)

B4T said:


> Because when they had high profile fires and people died the press was all over it...
> 
> Many houses were pigtailed.. but using standard wire nuts... they didn't know any better..


There is a huge difference between aluminum branch circuit conductors and service conductors. 

Yes for sure there was and remains a problem with a lot of the AL used as branch circuit conductors in the early 70s. 

I do not believe they every had such issues with feeder sized or service sized AL.


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## Dennis Alwon (May 9, 2009)

BBQ said:


> I do not believe they every had such issues with feeder sized or service sized AL.


How can that be if they were made of the same alloy. I always thought it was an issue with larger wires as well.


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## Cletis (Aug 20, 2010)

Dennis Alwon said:


> How can that be if they were made of the same alloy. I always thought it was an issue with larger wires as well.


I'm trying to find out now if SEU from 60/70's was exactly same stands as single strand branch ...stay tuned...for now here is some good reading on subject with ref's


Failure Mechanisms of Aluminum Wiring

M. Braunovic, "Fretting Corrosion Between Aluminum and Different Contact Materials," Electrical Contacts - 1977, Proceedings of the 23rd Annual Meeting of the Holm Conference on Electrical Contacts, Chicago, 1977.
M. Braunovic, "Effect of Fretting on the Contact Resistance of Copper, Aluminum, and Nickel-Coated Aluminum Wire Connections," Wear, V. 112, 1986.
N.T. Bond, D.L. Robinson, and M. Mohajery, "Fundamental Considerations of Aluminum Electrical Contact Interfaces," Elecrical Contacts - 1977, Proceedings of the 23rd Annual Meeting of the Holm Conference on Electrical Contacts, Chicago, 1977.
J. Aronstein, "Electromigration Failure of Aluminum Contact Junctions," Elecrical Contacts - 1995, Proceedings of the 41st Annual Meeting of the Holm Conference on Electrical Contacts, Montreal, 1995.
J. Aronstein, "Conduction in Failing Aluminum Connections," Electrical Contacts - 1990, Proceedings of the 36th IEEE Holm Conference on Electrical
Contacts meeting jointly with the 15th International Conference on Electrical Contacts," Montreal, 1990.
M. Leger, "Metallurgical Analysis of Failed CO/ALR Devices," Ontario Hydro, #78-54-K, Ontario, Canada, February, 1978.
J. Aronstein, "Failure of Aluminum Connections in Residential Applications," Elecrical Contacts - 1991, Proceedings of the 37th Annual Meeting of the Holm Conference on Electrical Contacts, Chicago, 1991.
J. Aronstein, "AC and DC Electromigration in Aluminum Contact Junctions," Electrical Contacts - 1996, Proceedings of the 42nd IEEE Holm Conference on
Electrical Contacts meeting jointly with the 18th International Conference on Electrical Contacts," Chicago, September 1996
Nickel Plated Aluminum Wire

H.O. Hansson, "Sinipal: Swedish-bred Aluminum Substitute for Copper Wire," Wire and Wire Products, September, 1970.
J. Aronstein and T.K. Hare, "Evaluation and Analytical Electron Microscopy Investigation of a Plated Aluminum Wire for Branch Circuit Applications," IEEE Transactions on Components, Hybrids, and Manufacturing Technology, V. 11, No.2, June 1988, p. 218-226
Copper-Clad Aluminum Wire

J.C. Fan, "An Examination of Copper Clad Aluminum Conductor for Circuit Size Wiring," Texas Instruments Inc., Metallurgical Materials Div., Wire Products Dept., Attleboro, MA.
Alloy Aluminum Wire

J. Aronstein and W.E. Campbell, "Evaluation of an Aluminum Conductor Material for Branch Circuit Applications," IEEE Trans. Components, Hybrids, and Mfg. Tech., V. CHMT-8 No. 1, Mar. 1985


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## Shockdoc (Mar 4, 2010)

Cletis said:


> I thought this thread was about service entrance cable. Now that I know old aluminum branch cir. that's a different thing. Obviously, someone didn't research the brittleness of old single strand aluminum nm...ooopss
> 
> Since you can't run aluminum "Generally" to branch circuits and they corrected brittleness problem what's the problem with the new aluminum ?? Superstition? Mis-information? Lack of Knowledge? or all the above and more ?
> 
> Did they put the alum on brass screws where the fire happened? dummies


Screws.....I came across homes where they used backstab only receptacles with the aluminum. Many did not care.


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## Big John (May 23, 2010)

Dennis Alwon said:


> How can that be if they were made of the same alloy. I always thought it was an issue with larger wires as well.


 Good point. I never really considered that. 

Maybe when it's stranded in larger conductors it removes some of the expansion problems single conductors experienced...?


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## bobelectric (Feb 24, 2007)

Suckered in to another pointless debate that would be a N.E.C. code change.


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## Celtic (Nov 19, 2007)

Dennis Alwon said:


> How can that be if they were made of the same alloy. I always thought it was an issue with larger wires as well.



Weren't the lugs also made of AL?


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## Big John (May 23, 2010)

Celtic said:


> Weren't the lugs also made of AL?


 Yeah, but weren't the device terminals as well? Maybe it goes back to poor installation in each case, and that the small conductors are just much less forgiving?


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## B4T (Feb 10, 2009)

BBQ said:


> I do not believe they every had such issues with feeder sized or service sized AL.


Anytime I see a PoCo guy at 7-11... I ask him about AL service conductors...

I always get a smile along with "job security or overtime"... from making repairs...

Granted... there is no way of knowing how old the AL conductors are... but if a customer is willing to pay for CU... so be it.. 

You also have plenty of manufactures saying .. "CU WIRE ONLY" on their equiptment... adding fuel to the fire..


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## Celtic (Nov 19, 2007)

Big John said:


> Yeah, but weren't the device terminals as well? Maybe it goes back to poor installation in each case, and that the small conductors are just much less forgiving?


I thought the device terminals were brass?


Bulldog said:


> It was the poor design and allowing the use of Al wire on brass terminals.


I do agree with careless installation and smaller conductors being less forgiving.


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## Cletis (Aug 20, 2010)

Tidbit 

Swedish Aluminum experiments

An experimental aluminum wire alloy containing *Mg* was among many tested in the *early 1970's* in research directed toward the solution of aluminum wire connection problems. Unlike other alloys tested at that time, its *performance in heat-cycle tests of splices* made with twist-on connectors was *equivalent to copper wire*. Enrichment of Mg at the wire surface appeared to account for the improved connectability of this alloy.


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## Dennis Alwon (May 9, 2009)

I probably have seen more aluminum service cables and feeders fail then I have aluminum branch circuit . Granted there is more load on the feeders and hence more problems, IMO. The branch circuit was another issue but I never installed aluminum wire for circuits under 40 amps.


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## Cletis (Aug 20, 2010)

Here are some nice cliffnotes pre-highlighted by moi for your viewing enjoyment from my good friends at Southwire. 

During this same time, and again due to materials shortages, the *brass screws in electrical devices were replaced with steel screws*. Once more due to the urgent nature and time constraints, driven by the need, this change also happened with a *lack of appropriate testing and listings*.

*No one thought* that a *compatibility issue *between *steel screws and aluminum wire existed*. However, the next decade would prove that a simple substitution of a screw without the appropriate testing can have consequences. The characteristics of each of the materials was such that under the heating and cooling experienced during operation, the device terminations could loosen resulting in high resistance connections and heating. Ultimately these connections resulted in residential fires, and the rest is history.

DURING THE 60’S AND 70’S PROBLEMS INVOLVED 10 AWG AND 12 AWG BRANCH CIRCUIT CONNECTIONS

The *most likely and often identified reasons for aluminum branch circuit failures were:*

*Workmanship*

Poor workmanship is generally recognized as the primary source of failed connections. Results of poor workmanship included incorrectly tightened connections, wires wrapped the wrong way around binding screws, and aluminum conductors used in push-in connections or with devices meant only for copper. If a connection was loose due to improper tightening torque, the connection would tend to loosen over time.

*Thermal expansion differences*

The coefficients of thermal expansion for aluminum and brass are similar while the thermal expansion for aluminum and steel is not. Copper’s thermal expansion is similar to both steel and brass. This is why the change to steel screws did not cause copper connector failures. Steel and aluminum have significantly different rates of thermal expansion. Because of this difference, the two materials expand and contract at different rates under load cycling. This causes the connection to gradually develop a smaller contact area resulting in increased resistance. As the resistance increased, the temperature at the termination point would also increase.

*Creep of a conductor*

Creep is a property of all metals, and each metal has a unique rate of creep. Creep is the measurement of the rate of change of a material’s dimensions over a period of time when exposed to a force at a particular temperature. The* old aluminum conductors used EC grade aluminum (AA-1350)* for building wire which has a *higher creep rate* than copper building wire. 

The difference in creep between aluminum and steel resulted in connector failures.

A NEW ALUMINUM…

In 1968 Southwire Company led the way in aluminum building wire technology with the advent of triple e® aluminum alloy, resulting in the very first AA-8000 series aluminum alloy. This change resulted in the higher aluminum standards that are still observed today. Starting with a clean slate, metallurgists developed an aluminum alloy that possessed the characteristics desirable in an aluminum building wire. In 1972, and for the first time, aluminum building wire was manufactured with its own metal, not a poor fitting hand-me-down from electrical utility applications. One alloy does not fit all!

This new aluminum alloy, developed and patented by Southwire, *bridged the gap in key metal characteristics between copper and aluminum. In AA-8000 series aluminum alloy characteristics such as elongation, thermal stability, compressive creep and flexibility were much closer to that of copper.* In addition to a new aluminum alloy, aluminum building wire and devices were being tested and listed for compatibility. The use of compatible materials, proper testing and listing resulted in a reliable aluminum electrical wiring method. In 1981, the NEC® began requiring aluminum alloy conductors for 12, 10 and 8 gauge conductors. In 1987 NEC® began requiring AA-8000 series aluminum conductors. This has remained unchanged and can be found in the 2008 NEC® Section 310.14. AA-8000 series aluminum alloy conductors have properties that are significantly different from the old AA-1350 aluminum conductors. To confirm your cable has these conductors, look for the designation “AA-8176” on Southwire’s cable print legend. For other aluminum building wire products, make sure there is an “AA-8…” followed by three other digits.

In addition, copper/aluminum compatible (CO/ALR) devices were required for aluminum wire branch circuits and listed by UL. These devices were developed to be compatible with 10 and 12 AWG aluminum conductors. Due to the cost of these connectors and devices, it is no longer economical to use these sizes in aluminum.

Today, aluminum AA-8000 alloy is fully recognized by industry standards and is required in all aluminum building wire installed per the NEC.® This new aluminum is generally compact stranded according to ASTM B-801. Compact stranding reduces the diameter of the conductor by 9-10%. Equal ampacity AA-8000 aluminum and copper conductors can usually be installed in the same size conduit because of the compact stranding. Annex C in the 2008 NEC® includes tables for determining conduit fill when using compact stranded conductors. These tables can be used for both compact stranded aluminum and copper conductors.

*FIRST IMPRESSIONS ARE HARD TO CHANGE*

Even though aluminum was poised for the comeback it deserved, market conditions and lack of understanding prevented it from reaching it’s full potential. Copper prices at the time were relatively low so little motivation existed to try something new. First impressions are hard to change and although some considered it as a new alternative, others still perceived it as the same wire used in the 50’s and 60’s.

Aluminum building wire is something few people in the residential and commercial electrical industry don’t have a passionate opinion about. More often than not, you will find this opinion is based on *40-year-old facts, and a misunderstanding of those facts*. Aluminum building wire, through the efforts of manufacturers like Southwire, and organizations such and the NEC® and UL,® is a proven safe and reliable system.

And don’t forget about the advantages of aluminum building wire over copper, particularly in the larger sizes (6AWG- 900kcmil). It is much lighter and more economical. This means *easier installations, fewer injuries, and pound-for-pound more conductivity*. Those that have embraced feeder sized aluminum building wire, are reaping the benefits, and may very well be hoping you walk away from this information clinging tight to your old misconceptions since they could be bidding their next job against you.

So why tell this story? With the rise in copper prices over the past few years renewed interest in aluminum building wire is gathering. Many contractors and owners find themselves looking for an alternative to provide relief from rising copper prices. Unfortunately, they are still being misinformed that the very solution they hope for does not exist. Well it does and it has for over 35 years. It’s called AA-8000 series aluminum alloy. And Southwire Company developed it in 1968. So now when you hear someone say “aluminum causes fires” you can reply with the facts about today’s aluminum building wire:

*A problem that happened 40 years ago*, *failure of utility grade aluminum* and a *simple steel screw*, is simply not relevant to the aluminum building wire installed today. With the development of an improved aluminum alloy, AA-8000, increased NEC® and UL® requirements, and a proven track record of over 30 years, aluminum building wire is just as safe and just as reliable as copper.

DID YOU KNOW?

• Material shortages after WWII and a housing boom in the 1960’s caused the switch from copper to aluminum in building wire.

• Pre-1972 aluminum wire is referred to as either AA-1350 aluminum, EC aluminum or utility grade aluminum because it was the same construction used in utility wire.

• The National Electrical Code® has permitted the use of aluminum wire since 1901.

• Southwire developed and patented the first AA-8000 Series aluminum alloy in 1968 setting a standard for the manufacturing of aluminum building wire that exists today.

• In the 80’s, UL® and NEC® required new connectors and devices assuring reliability of aluminum building wires performance.

• It takes only one pound of aluminum to equal the current-carrying capacity of two pounds of copper.


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## Bulldog (Jan 28, 2009)

I agree that brass screws were replaced with steel screws. The problem would have still existed if it was not changed. 
Aluminum and brass have different coefficients of expansion.

Al has a linear coefficient of expansion of 23x10^(-6)/degree C

Brass has a linear coefficient of expansion of 20x10^(-6)/degree C

The Al will respond more (change more in size) than the Brass with temperature. If you cool the assembly, the Al nut will shrink more than the Brass bolt, and thus get stuck tighter. However if you heat the assembly, the Al nut will expand more than the brass bolt, and cause a separation of the two so that removal will be easier.

With a brass nut on an aluminum bolt, again, the Al changes more in size with temperature. So in this case, if you cool the assembly, the Al bolt will shrink more than the brass nut, and will cause a separation between the two and make the nut easier to remove. if you try to heat it, the Al bolt will expand more than the Brass nut, and will get stuck even greater.

This brings now to Al service conductors. It is very important to make sure connections are torqued to proper specfication. If not there is a better chance that the connection will loosen up over time.


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## electricmanscott (Feb 11, 2010)

B4T said:


> Anytime I see a PoCo guy at 7-11... I ask him about AL service conductors...
> 
> I always get a smile along with "job security or overtime"... from making repairs....


How many times did this fantasy occur? :laughing:


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## electricmanscott (Feb 11, 2010)

Peewee0413 said:


> *Aluminum is not always safe. If not installed properly(loose connections),* aluminum oxide is not conductive. Which will cause the fires ..aluminum can be safe. Just not as safe as copper.


Should have stopped right there.


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## BBQ (Nov 16, 2010)

B4T said:


> Anytime I see a PoCo guy at 7-11... I ask him about AL service conductors...
> 
> I always get a smile along with "job security or overtime"... from making repairs...


They live in a very small corner of a large country. Most of the US distribution system is AL and trouble free.

We do have some ocean side towns that the power company uses copper due to the salt in the air.





> if a customer is willing to pay for CU... so be it..


No doubt, we install a lot of copper by request but having it agaist the rules for large areas is dumb.



> You also have plenty of manufactures saying .. "CU WIRE ONLY" on their equiptment... adding fuel to the fire..


That is to save money from having to pay for additional tests for the listing.


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## RePhase277 (Feb 5, 2008)

Ah, the old aluminum vs. copper debate. This ranks between Kirk vs. Picard and Santa vs. The Martians on my list of insanely fu**ing stupid arguments about absolutely nothing.


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## Shockdoc (Mar 4, 2010)

I prefer copper clad steel conductors.


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## BBQ (Nov 16, 2010)

InPhase277 said:


> Ah, the old aluminum vs. copper debate. This ranks between Kirk vs. Picard and Santa vs. The Martians on my list of insanely fu**ing stupid arguments about absolutely nothing.


Yet you took the time to comment on it.

And by the way, Kirk and Santa obviously.


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## Tom45acp (Sep 6, 2011)

BBQ said:


> Yet you took the time to comment on it.
> 
> And by the way, Kirk and Santa obviously.


Ginger or Maryann?


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## backstay (Feb 3, 2011)

Tom45acp said:


> Ginger or Maryann?












Here's my vote.


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## BBQ (Nov 16, 2010)

Tom45acp said:


> Ginger or Maryann?


Mrs Howell.


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## RePhase277 (Feb 5, 2008)

BBQ said:


> Yet you took the time to comment on it.
> 
> And by the way, Kirk and Santa obviously.


You goddamn right I did. Twice. And will do it again on the next insanely stupid argument about absolutely nothing:thumbup:


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## hardworkingstiff (Jan 22, 2007)

InPhase277 said:


> You goddamn right I did. Twice. And will do it again on the next insanely stupid argument about absolutely nothing:thumbup:


So how do you feel about ground up or down? :laughing:


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## RePhase277 (Feb 5, 2008)

hardworkingstiff said:


> So how do you feel about ground up or down? :laughing:


I feel very good about it, thank you.


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## Chris1971 (Dec 27, 2010)

As of today, I'll bid it as a copper install but, we'll continue to install aluminum until the lineman at 7-11 tell me otherwise.:laughing::laughing:


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## 37523 (Dec 30, 2012)

> _Loose copper connections aren't exactly great either._

Contacts are a big problem in all electrical work. All the cheap metals have oxides that conduct poorly. Noble metals (gold) don't tarnish but tend to be soft. 

Copper vs. Aluminum: 

Copper oxide is a poor conductor, but not an insulator either, and is soft. A poor contact tends to either burn-through the oxide or oxide-up to an open circuit. In another life I have abused copper-oxide rectifiers, they break-down easy. Copper oxide problems tend to be manageable, in benign atmosphere, with good pressure. (But if you jiggle the loose contact under load, you can get a microscopic spot-weld which leads to a glowing contact, bad.) 

Aluminum Oxide is an excellent insulator and very hard (rubies, sapphires, corundum). If you brush-break the oxide, apply anti-oxide, and keep it well-clamped, you get a fine connection. Also if the aluminum is plated (copper, tin) or doped with other metals (8000 series alloys) the oxide issue is reduced. There are also now CO/ALR devices with extra "bite" to work through Al oxide and "give" with thermal cycling. 

Common-grade Aluminum "creeps". Like Lead, if you keep pressure on it, it smooshes. All metals do, but Copper much less than common Aluminum. Once this was seen as a problem, electrical Aluminum was alloyed for low creep. NEC requires special alloys for branch wiring from 1981. 

Intermetallic compounds (alloys of aluminum and steel) are also a problem. 

UL improved their Aluminum connector standard in 1978. 

There's differences between devices and services. Your helper does 200 device screws real fast. Any 15A device may have 21 Amp loading. OTOH you do the 3 or 9 service clamps with a bit more care. Large-gauge service clamps use large screws and plates. 200 Amp service rarely really has 60-100 Amp loading. 

Overall: because Copper *tends* to be more forgiving of lax connections, workmanship that was "OK" 1880 through the 1960s became marginally "not-OK" (and sometimes disastrous) when Aluminum came in, and it was not until the 1980s that wire and connectors for Aluminum became more slop-proof. 

> _use of Al wire on brass terminals. ...Brass screws will expand faster than Al wire._

Device screws are iron. The "brass" color is hardly skin-deep; the screw expands like iron. 

One reference implies steel screws became common in the 1960s. 
Also "Almost all reported {Aluminum} problems involved 10 AWG and 12 AWG branch-circuit connections..."
http://www.iaei.org/magazine/2006/01/aluminum-building-wire-installation-and-terminations/

Thermal expansion: 
Copper = 9.3 
Aluminum = 12.3 
Steel = 7.3 

Ratios: 
Copper under steel: 1.3:1
Alumin under steel: 1.7:1

> _they used backstab only receptacles with the aluminum. Many did not care._

Too true.


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