ALUMINUM WIRE

By Christopher Crowe

According to the US Consumer Product Safety Commission (CPSC), homes wired with aluminum wire are fifty-five times more likely to have one or more connections reach fire hazard conditions than homes wired with copper

Aluminum wire was used for branch circuits starting in the late 1950s and used through the mid-1970s. Copper-tinned wire and aluminum wire are both silver colored. Copper-tinned wire has a core of copper and a thin tin outer shell. Aluminum wire was encased with a plastic jacket, while copper-tinned wire was encased with a cloth-braided jacket.

For a given ampacity a larger aluminum wire than copper is required. Usually, an aluminum wire one size larger is required compared to copper. Mechanical problems and points of failure usually occur where the older aluminum-alloy wire connects to the outlet or switch.

All electrical connections rely on pressure. Loose connections at devices can cause arcing and overheating. Older aluminum wire is soft and has a greater tendency for thermal expansion than copper wire. The aluminum wire expands and the dimension changes as current heats it. When the current stops and the wire cools it can contract and leave gaps between the conductor and the terminal. This process, referred to as "cold flow," is typically the cause of arcing and overheating. Aluminum oxide, which acts as an insulator, is also a result of loose connections. It is always a good idea to have anti-oxidant paste on all aluminum wire terminations.

Changing the outlets and switches to devices that are rated for direct contact to aluminum wire can be effective if done by a qualified electrician. The devices must be labeled "CO/ALR." Devices that are labeled "CU Only," "Cu/Al," or devices that are not labeled at all, are not acceptable and should be replaced with devices that have the "CO/ALR" label. This can cost from $600 to $2,000 depending on the number of devices being replaced.

Connecting a copper wire "pigtail," which terminates at the device to the aluminum wire is another option. The Copalum system from Amp Industries connects the copper to the aluminum with a special crimping die tool. The die acts as a conductor so the copper and the aluminum do not have contact with each other. The connection is then insulated with heat-shrink tubing.

Even though this method is approved by the Underwriters Laboratories and endorsed by the CSPC, it is not without its detractors. The repeated bending of the wire during the retrofit can damage the wire, especially wire that was manufactured before 1972. Only contractors trained by Amp Industries and those who lease Amp equipment may install the system. The average cost is about $45 per device. Depending on the number of devices in a home, a retrofit can cost anywhere from $2,500 to $7,000.

Connecting the copper "pigtail" to the aluminum wire with a wire nut is another method that contractors use. The purple "Ideal 65" wire nut is listed for copper-to-aluminum contact but not aluminum-to-aluminum connections. No other wire nuts are listed for this application. One problem with using wire nuts for "pigtailing" is that in most cases the box will be overfilled and not in compliance with the National Electrical Code (NEC). The Ideal 65s also have their detractors, as documented on the website at The Home Inspection & Construction Information Website.

All of these methods have been used with varying degrees of success and failure. Who does the work is just as important as what method is used. Even copper wire systems fail if not installed correctly by qualified personnel.

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