Can You Hook Up an Aluminum Wired Light Fixture to Copper Wiring?

Aluminum Wiring

• A copper shortage in the 1960s led wiring suppliers to begin manufacturing residential electrical wiring from aluminum, but the practice was soon discontinued as it became evident that aluminum wiring poses a fire risk. The risk is most pronounced at junctions to fixture boxes and outlets where the overheated wire can melt and even ignite plastic components. Aluminum wire alloys, introduced around 1972, are less prone to overheating but are still considered unsafe for residential branch circuits. The code currently allows the use of aluminum wiring only for some single-purpose high-amperage applications, including the wiring for the main service panel.

The Risk

• Aluminum has a higher coefficient of expansion than copper, which means that it expands more when it heats up and contracts more when it cools down, even permanently shrinking after repeated cycles. Consequently, the wire can eventually work itself loose from its connections. Therefore, even if the high heat generated by the electrical resistance of aluminum wire isn't enough to damage fixtures, arcing from loose connections may do it instead. The U.S. Consumer Product Safety Commission (CPSC) found that homes built with aluminum wiring before 1972 were 55 percent more likely to have fire hazards at the fixtures that other homes.

Connecting Copper and Aluminum Wiring

• Short of replacing all aluminum wiring with copper, the CPSC considers only one wiring method safe when you must connect aluminum and copper wires, and that is to use COPALUM connectors. Trained electricians use special tools to crimp these connectors onto the aluminum wire, breaking through the oxidation layer to prevent corrosion and making a permanent connection. Although it doesn't recommend them, the CPSC considers AlumiConn connectors as the best alternative. They use a setscrew type connector and do not have to be installed by a licensed professional, but the CPSC does not consider them 100 percent safe.

Warning

• Conventional wiring methods are not suitable for splicing aluminum wire to copper. Twist-on wire connectors intended for copper wiring are vulnerable to overheating and should be avoided. The same is true for conventional crimp connectors. Because of the difficulty of joining copper and aluminum wiring, it may be worth your time to examine the lamp to see if you can replace the aluminum connection wires with copper ones. If so, do it only if you are sure that the interior wiring of the fixture isn't aluminum. If it is, your fixture may overheat without warning and start a fire.