Why it shouldn’t play second fiddle to copper wiring

By Tom McDonough

In the 1960s, newspapers often carried headlines such as House Fire Caused by Faulty Aluminum Wiring. That’s because aluminum wiring, touted as a less costly alternative to copper wiring — which at the time was in short supply and carried a hefty price tag — was identified as the culprit in numerous residential fires across the nation. It got so bad that in 1974, the U.S. Consumer Product Safety Commission issued a warning on the hazards of aluminum-wire electrical systems and sued dozens of manufacturers.

“That was really a bad rap,” says Terry Blinkhorn, Purchasing Agent for Parsons Electric LLC. “Aluminum wiring got the blame, but it wasn’t necessarily the aluminum conductor. It was the connectors used for terminations that were causing the problems. When used and terminated correctly, aluminum wiring is safe and dependable and can save money.”

Jeff Starkman, President of ElectroTech Inc., Minneapolis, a company that markets electrical products throughout the Midwest, agrees. “Aluminum conductors have been used to carry electricity since the late 1800s, especially in utility applications,” he says. “All the conductors utility companies use outside in their power grids are aluminum because of the great lengths they must be strung. In the 1960s, when aluminum conductors were first being used in residential branch circuit applications, often times the set screw terminals were made of steel or brass. These metals have significantly different thermal characteristics, and therefore were not suitable for landing aluminum conductors.

Problem and solution

When aluminum conductors were connected to those steel and brass terminals, the conductor would heat under load and expand at a faster rate than the steel or brass terminals. Over time, the conductor could become deformed under the screw terminals, creating air gaps, which could lead to arcing within the connection. This could create a high-resistance junction that led to overheating, sparking, and possible fires.

According to Al Palmer, the local representative for Southwire Company, Carrollton, Georgia, who manufactures aluminum building wire and MC Cable, that problem is ancient history. “After organizations, such as Underwriters Laboratories and the Aluminum Association, investigated, changes were made and standards were changed. In 1968, Southwire was the first company to patent a new aluminum alloy, AA-8000, which provided increased flexibility and better thermal stability of the conductor. The AA-8000 alloy is now the standard for the industry and provides improved electrical and mechanical characteristics as well,” he explains.

Lighter weight and increased flexibility of aluminum wire translates into time and labor savings.

The new aluminum alloy proved so good that in 1987 the National Electrical Code — developed by the National Fire Protection Association and the world’s most widely adopted safety code — mandated that only 8000-series aluminum wiring be used in building wire applications.

Connector Manufacturers also redesigned the connectors that caused the problems in the troublesome 1960s, constructing the connectors from metals that expanded and contracted at rates similar to aluminum. These new connectors are rated for usage with either copper or aluminum conductors and have become the industry standard. These dual-rated connectors are designated as AL7CU (for 75o C) and AL9CU (for 90o C).

Adding value

Building owners and contractors can realize distinct benefits when installing aluminum wiring. Most important is the cost. Historically, aluminum wire is about half as expensive as copper.

“Right now, with copper prices high, some of our customers are experiencing as much as a 70 percent savings on aluminum wire over copper,” Starkman says.

For electrical companies such as Parsons, the additional benefits of lighter weight and increased flexibility of aluminum wire translates into time and labor savings. “With aluminum conductors, you can move the coils around more easily, and it requires less labor to build a system,” Blinkhorn says.

One of the hottest trends in the industry for installing commercial building electrical systems is the use of metal-clad, or MC, cables. An MC cable is three or four conductors twisted together inside an aluminum-armor sheath. By using MC cables, contractors can eliminate building conduit duct systems. “With MC cable, you simply pull it off the reel and secure it as you would a normal conduit system,” Starkman says. “You reduce all the time it takes to build a conduit system. In fact, the labor savings available by using the MC cable systems has been estimated to be in excess of 50 percent when compared to a traditional cable in conduit systems.

“Labor costs are high now, and contractors don’t win jobs or earn profits only on material costs,” Starkman says. “They earn profits by utilizing their labor better than the next guy, and MC cable can help them do that. Once a contractor gains experience working with MC cable, the labor hours needed to install an aluminum electrical feeder cable system are significantly less than with a copper-based system.”.

More misconceptions

	Historically, aluminum wire is about half as expensive as copper (shown here).

Contractors often mistakenly believe that when they build a conduit system for a project they need to increase its size to make room for the larger-diameter aluminum conductors. In order to maintain the same ampacities when converting copper conductor to aluminum, the conductor must be upsized. Manufacturers of aluminum conductors have compact stranded the conductor to afford very similar conduit fills as copper conductors. For example, while a 500 MCM aluminum conductor is required to replace a 350 MCM copper conductor, the allowable conduit fill between the materials is the same because manufacturers have reduced the diameters of the aluminum conductors by compact-stranding.

Aluminum building wire manufacturers use compact-stranding, which allows the contractor to run the same number of conductors in the same size conduit as copper the majority of the time.

“Once a contractor or engineer uses aluminum building wire, they soon realize the benefits of cost savings on both labor and material.” ~ Al Palmer, representative, Southwire Company

Another aluminum wiring fallacy is that it requires extra labor to terminate because of aluminum’s oxidation characteristics. All metals — with few exceptions, such as gold — oxidize freely when exposed to the air, including copper. With aluminum wire, aluminum oxide can act as an insulator, impeding the flow of electricity. It is easily removed by wire brushing as the aluminum oxide is very brittle. However, proper termination techniques are important no matter what material is employed. The practice of wire brushing and the use of anti-oxidant pastes are recommended for copper and aluminum conductors by conductor and connector manufacturers.

Whether an electrician or a contractor uses aluminum or copper wire, proper installation is the key. “Wire brushing the oxidation and using an anti-oxidation paste on the connections when landing the conductors can solve that concern,” Starkman says. “Moreover, torquing the connections to the manufacturer’s specification is critical. If you over-torque the connectors, you can damage the strands, and if you under-torque, you won’t get the full bite on the connector. Torque the connections properly whether it’s aluminum or copper wire, and you’ll never have a problem.”

A change of heart

Engineers and contractors are rediscovering the value of aluminum conductors and connectors as wire manufacturers continue to explore new cable construction and processes to add value and make their products more efficient. “There are numerous building applications for aluminum wire, and in 2006, we saw evidence of this with record demand for aluminum building wire conductors,” Palmer says. “We find that once a contractor or engineer uses aluminum building wire, they soon realize the benefits of cost savings on both labor and material.” Field personnel find it is easier to handle and install on the jobsite than copper conductor and also learn that aluminum conductor is just as dependable as copper, which leads to repeat use from the contractor.