[Bad Electrician]

In researching a paper I am putting together for revamping maintenance practices I came across the following worth the read.

http://www.aluminum.org/sites/default/files/Aluminum%20Building%20Wire%20Installation%20%26%20Terminations.pdf

http://www.aluminum.org/resources/electrical-faqs-and-handbooks/electrical

In Particular

FAQs and Answers For Aluminum Alloy Building Wire
Q1) What are the relative conductivities of aluminum and copper?

Aluminum has 61% the conductivity of copper on a volume basis and 200% the conductivity of copper on a weight basis.
- See more at: http://www.aluminum.org/resources/electrical-faqs-and-handbooks/electrical#sthash.rbQYkAju.dpuf

Q3) Why is copper used more often for smaller wire sizes?

Copper, having been available to mankind for thousands of years, was readily available at the beginning of the electrical industry in 1882. At that time, aluminum was only available in very small quantities, so it was a precious metal more valuable than gold or silver. Ninety-five percent of all the aluminum ever produced was made after WWII; and by then, the electrical industry had developed using copper. Over the past few decades, aluminum has increasingly replaced copper for electrical applications. The transformation started on the utility grid thru transmission, distribution, and has continued down to service drop, service entrance and building wire feeders.

In the United States today, copper is typically the only choice available for branch circuit wiring. Receptacles and switches are usually rated only for copper, and are less expensive than CO/ALR devices. - See more at: http://www.aluminum.org/resources/electrical-faqs-and-handbooks/electrical#sthash.rbQYkAju.dpuf

Q4) Is there a certain kind of aluminum that must be used for building wire?

Yes. In most cases, you must use an AA-8000 series aluminum alloy building wire as required in NEC 310.14. There are some exceptions, notably underground service entrance conductors that terminate outside a building. - See more at: http://www.aluminum.org/resources/electrical-faqs-and-handbooks/electrical#sthash.rbQYkAju.dpuf

Q9) Is joint compound required to be used on aluminum to prevent corrosion?

Only if the connector manufacturer or local codes specifically require it. The NEC does not require oxide inhibitor for either aluminum or copper, but it does require that you follow manufacturers’ installation instructions for listed products.

However, even if oxide inhibitor is not specifically required, it is recommended for both aluminum and copper conductors to prevent ingress of moisture and the possibility of subsequent corrosion. Both copper and aluminum conductors will corrode if installed in corrosive environments. Proper installation and choice of connector help to prevent corrosion at connections.

Oxide inhibitors are also tested for specific uses. Be sure to follow manufacturers recommendations and use only inhibitors specifically listed for the conductor type and voltage class you are installing.

Q10) Do aluminum connections need to be periodically tightened to maintain a good electrical connection?

No. Connections on either aluminum or copper should not be retightened after installation following manufacturers’ installation instructions. Connector test performance requirements are based upon no retightening. NFPA 70B, Recommended Practice for Electrical Equipment Maintenance, does not call for retightening aluminum conductors. Connections should only be tightened if there is evidence of a loose connection. Both over-tightening and under-tightening can cause failure of aluminum or copper connections. Unwarranted re-tightening of screw-type connectors can lead to failure of the connection with either aluminum or copper conductors - See more at: http://www.aluminum.org/resources/electrical-faqs-and-handbooks/electrical#sthash.rbQYkAju.dpuf

 

[Big John]

Interesting trivia, apparently the reason that aluminum doesn't rust is actually because it oxides so incredibly fast. When raw aluminum is exposed to air it very quickly forms a thin, hard coating of aluminum-oxide, and this actually protects the metal underneath helping prevent noticeable rusting.

 

[JRaef]

Conspicuously left out of that discussion is the fact that aluminum conductors expand and contracts with temperature change at a much much higher rate than copper. This leads, over time and thermal loading cycles, to aluminum conductors having a known issue with developing bad connections. The closest they get to addressing it is in the comment about whether or not one must re-tighten connections. They respond by basically saying it is the connector mfr's responsibility to make a connector that does not need tightening. This is technically true, but ignores the reality of how the world works.

 

[Big John]

...They respond by basically saying it is the connector mfr's responsibility to make a connector that does not need tightening. This is technically true, but ignores the reality of how the world works.

I'm very much of the opinion that an aluminum conductor torqued to the proper termination specs will never need re-tightening. What's the point of using a rated listed termination if it can't accommodate the normal thermal expansion of the conductor?

 

[Bad Electrician]

In my experience based on our IR Scanning we see no more issues with aluminum than we do with copper.

And realize 95-99% of this copper has been over torqued, the old Allen Wrench with 24" 1" EMT.

 

[Shockdoc]

Aluminum is my friend.
I wish 12/2 cu clad would make a comeback.

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[Meadow]

Aluminum is your friend in the right places. Perhaps Id skip out on mission critical supply's, but every day work you bet its cheaper.

 

[Meadow]

I think the first article hits the nail on the head. 10 and 12 guage aluminum branch circuits in the 70s were made from "utility grade aluminum". It was this mistake that gave aluminum a black eye creating the whole a fiasco. Utility grade aluminum (designed to be ultra cheap for overhead lines) is very, very different from standard aluminum wire used today for 600 volt and under home runs. IMO late 60s and 70s solid aluminum wire for 15 and 20 amp circuits should be ripped out, but the other stuff is ok. And its this that creates confusion.

 

[Shockdoc]

Aluminum is outlawed in residential past the service equipment in my jurisdiction. I would love to see that changed.

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[BababooeyHTJ]

Conspicuously left out of that discussion is the fact that aluminum conductors expand and contracts with temperature change at a much much higher rate than copper. This leads, over time and thermal loading cycles, to aluminum conductors having a known issue with developing bad connections. The closest they get to addressing it is in the comment about whether or not one must re-tighten connections. They respond by basically saying it is the connector mfr's responsibility to make a connector that does not need tightening. This is technically true, but ignores the reality of how the world works.

Yup, copper is also a far better conductor of heat. So it'll help wick heat away from something like a loose connection.

 

[stuiec]

Yup, copper is also a far better conductor of heat. So it'll help wick heat away from something like a loose connection.

to where?

 

[BababooeyHTJ]

Further down the wire. Instead of pretty much sitting just at the fault. More surface area means more heat dissipation. Could make a difference in how long there is an issue. Probably more of a difference with smaller gauge wire.

Just a theory.

 

[magitrician]

Interesting read. Banned in my jurisdiction for residential. Over time with heat connections get loose. If you've ever tightened lugs after 30 years you'll know why!

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[mayanees]

Critical power aluminum

Aluminum is your friend in the right places. Perhaps Id skip out on mission critical supply's, but every day work you bet its cheaper.

I've actually used aluminum at Data Centers for a well-known internet retailer on 480 Volt, 3000-amp transformer secondary's, at their insistence. Their rationale was that it's a dual-service feeder that's isolatable, and with provisions for IR scans at the termination points, inspections could identify any hot spots that could be easily addressed. The cost savings was significant, and I've not seen any problems in the 5 years since it was installed.

 

[don_resqcapt19]

I think the first article hits the nail on the head. 10 and 12 guage aluminum branch circuits in the 70s were made from "utility grade aluminum". It was this mistake that gave aluminum a black eye creating the whole a fiasco. Utility grade aluminum (designed to be ultra cheap for overhead lines) is very, very different from standard aluminum wire used today for 600 volt and under home runs. IMO late 60s and 70s solid aluminum wire for 15 and 20 amp circuits should be ripped out, but the other stuff is ok. And its this that creates confusion.

Actually the aluminum that causes the problems was prior to 1973 or 74. In late 73 or 74, they started using the new alloy for #10 and #12 aluminum conductors. When the new alloy was used with CO/ALR devices there were no more problems than you would have with a copper wiring system.

These sizes were only on the market for a couple of years because, based on the number of failures of the older aluminum conductors, no one wanted to take the risk using the new conductors and devices.

I kind of thought as the price of copper kept going up that one of the aluminum manufacturers would put the 15 and 20 amp aluminum conductors back on the market, but that did not happen.

 

[Bad Electrician]

Further down the wire. Instead of pretty much sitting just at the fault. More surface area means more heat dissipation. Could make a difference in how long there is an issue. Probably more of a difference with smaller gauge wire.

Just a theory.

Aluminum for the same size feeder has a larger surface area.

 

[Bad Electrician]

Aluminum is your friend in the right places. Perhaps Id skip out on mission critical supply's, but every day work you bet its cheaper.

More than likely the main service lateral is aluminum.

 

[BababooeyHTJ]

Aluminum for the same size feeder has a larger surface area.

True but its not sized to the difference in thermal conductivity but electrical conductivity. Copper transfers heat almost twice as well as aluminum.

Again probably more of an issue with smaller wire like the old aluminum romex.

 

[Bad Electrician]

True but its not sized to the difference in thermal conductivity but electrical conductivity. Copper transfers heat almost twice as well as aluminum.

Again probably more of an issue with smaller wire like the old aluminum romex.

Actually from my stand point there is no reason for a bad connection, you hire my firm we do a IR/Thermographic Scan, and we repair*1. NO BAD CONNECTIONS.

I did a google search for thermal properties of copper and aluminum and this discussion is in car forums, computer forums (heat sinks) and another forum that the topic I did not catch. Oh and electrical forums.

*1- And repair does not mean just a tightening of the hardware.

 

[FrunkSlammer]

I have yet to figure out why electricians, who make their money installing, maintaining, fixing and replacing electrical equipment, are so insistent on installing something that will last much longer than their careers and never require maintaining, fixing or replacement.