Tricks Of The Trade: The Differences Between Aluminum And Copper

By James C. Elledge, IFMA Fellow, CFM, FMA, RPA, RIAQM
Published in the November 2011 issue of Today’s Facility Manager

Q Are there performance or safety differences for aluminum versus copper when used in primary or secondary power electrical panels?

Michael Wahl
Associate Director Capital Planning, Design & Construction
California State University
San Bernardino
San Bernardino, CA

A Yes, there are performance differences for aluminum versus copper wiring. There can also be a safety issue if the wiring is not installed and terminated properly.

The National Electric Code (NEC) provides specifications for aluminum wiring (AA-8000 series electrical grade aluminum alloy) and the minimum conductor size. Usually, aluminum wiring is larger when compared to copper wiring size. A copper wire may be listed as 14 AWG, while the aluminum would be 12 AWG. This is covered in Article 310 of the NEC.

Aluminum wiring has been used in electrical wiring since 1901, just four years after the first edition of the NEC was published in 1897. Since 1982, the NEC has required aluminum alloy conductors for branch circuit wiring (12-8 AWG). AA-8000 series aluminum conductors, manufactured according to ASTM B-800, were first specifically required by the NEC in 1987.

And according to the International Aluminum Institute, aluminum is particularly suited to the following uses because of its high electrical conductivity, low weight, and good resistance to corrosion.

Transmission and distribution lines. Worldwide, most high voltage overhead transmission and distribution lines—as well as many underground lines–are made of aluminum.

Since 1945, aluminum has replaced copper in high voltage transmission lines and today is the most economical way to transmit electric power. Aluminum weights only one third of copper, and one kilogram of aluminum can carry twice as much electricity as one kilogram of copper. Aluminum power lines are therefore lighter and require fewer and lighter support structures.

Electric lights, motors, appliances, and power systems. Almost all electric lights, motors, appliances, and power systems depend on a vast grid of aluminum wire. For example, the power systems of the world’s largest buildings are made of aluminum.

Switchyards and substations. Aluminum is also widely used in switchyards or substations where electricity is stepped down to lower voltages for local distribution.

Light bulb bases. Since the 1950s, aluminum has practically replaced brass as the standard base for the electric light bulb. Every year in North America, more than four billion light bulbs, fluorescent tubes, and other electric lamps are manufactured, and 95% of them have aluminum bases.

All questions have been submitted via the “Ask The Expert” portion of the magazine’s web site. To pose a question, visit this link.