TFM Columnist Jim Elledge puts forth the case for copper vs. aluminum wire connected to main electrical switch gears.
By James C. Elledge, IFMA Fellow, CFM, FMA, RPA, RIAQM
Published in the January 2008 issue of Today’s Facility Manager
Q: I have a question about aluminum vs. copper electrical wiring—particularly when connected to large, main electrical switch gears. I have been told that “in the old days,” large aluminum main feeders (connected to switch gears) would expand and contract over time, and their lug connections would become loose. This would create a huge problem (and fire risk) for any building. According to an electrical contractor involved in one our projects, the new aluminum conductors are designed much better and don’t have this problem anymore.
My company’s standard practice for 20 years has been to use copper conductors, but with the price of copper going through the roof, we’d save a huge amount of money by using aluminum.
My chief engineer had some problems with aluminum in an older building and wants to stick with copper. But since code allows either, I wanted to investigate all of my options. What’s your opinion?
Name withheld upon request
A: Here are a few excerpts from a 1995 white paper from Copper.org that make the case for copper:
“Copper is recognized as the quality product, while aluminum is mainly used because it is cheaper. It [aluminum] has been successful mainly in office buildings and shopping centers where cost pressures are greatest, and where quality materials are sometimes squeezed out in the bidding process.
“Copper’s unquestioned superiority over aluminum building wire is at the point of connection. Although improved aluminum building wire materials have been developed to alleviate the tendency for connections to loosen as the metal ‘cold creeps,’ no amount of alloying will change the inherent nature of aluminum to immediately form, upon exposure of a fresh surface to air, a tightly adherent, high resistance oxide film.
“A survey of U.S. electrical contractors on their preference of building wire materials showed that they preferred copper 20 to 1 over aluminum. The only reasons for using aluminum were for lower first cost and light weight. Copper was considered superior in all other respects.”
Now for the other side of the argument, from Christel Hunter, a senior field applications engineer with Alcan Cable:
“Aluminum wiring was evaluated and listed by Underwriter’s Laboratories for interior wiring applications in 1946; however, it was not used heavily until 1965. At that time, copper shortages and high prices made the installation of aluminum branch circuit conductors an attractive alternative.
“As aluminum wire was installed more frequently, the industry discovered that changes were needed to improve the means of connecting and terminating smaller aluminum wire. The use of steel screws with utility grade aluminum wire resulted in a connection point that was more sensitive than copper or aluminum wire terminated with the previously used brass screws. Almost all reported problems involved 10 AWG and 12 AWG branch circuit connections.
Several factors led to the reported failures of aluminum conductors with steel screws. One of the most often cited reports on aluminum wiring, “The Report of the Commission of Inquiry on Aluminum Building Wire,” evaluated information published between 1941 and 1978 and identified 19 different factors that might have affected the contact resistance of aluminum wiring. The most likely and often identified culprits were: workmanship, thermal expansion differences, and creep.
“However, newer AA-8000 aluminum alloys have creep rates very similar to copper building wire. This means that AA-8000 conductors perform very much like copper conductors at terminations.
“Corrosion is often cited as a contributing cause of failure at aluminum connections. Nowadays, a thin, protective layer of oxide on aluminum conductors contributes to the excellent corrosion resistance of aluminum. When terminations are made correctly, the oxide layer is broken during the termination process, allowing the necessary contact to be made between conducting surfaces.
“Furthermore, AA-8000 series aluminum alloy building wires are manufactured according to ASTM B-800. In the U.S., they are generally compact stranded according to ASTM B-801. Equal ampacity AA-8000 aluminum and copper conductors can usually be installed in the same size conduit.”
The early installers of aluminum tended to use the wrong product to save money. That’s an easy enough problem to solve, but when someone has a bad experience with aluminum, it is very difficult to get that person to use it again. Maybe this is what happened to your chief engineer.
So what have we learned? I think we’ve busted the myth that aluminum wiring is unsafe and should never be used for commercial purposes. If you use the right product for the job and follow proper installation practices, aluminum wiring may be up to the test. With copper demand so strong worldwide, it might not be such a bad idea to consider aluminum as a viable option for large wiring projects.
Elledge, facility/office services manager for Dallas, TX-based Summit Alliance Companies, is the recipient of the Distinguished Author Award from the International Facility Management Association (IFMA), is an IFMA Fellow, and is a member of TFM’s Editorial Advisory Board. All questions have been submitted via the “Ask The Expert” portion of the magazine’s Web site. To pose a question, visit this link.