Aluminum wiring was used in the 1970's for the wiring of receptacles and switches. Single-stranded branch aluminum wiring has been implicated with fires in houses. Aluminum does not conduct electricity as efficiently as copper and creates more resistance and heat. The wire expands and contracts more than copper. The problem was compounded by screw heads that were too small at the devices. This expanding and contracting are susceptible to working the connections loose at the receptacles and switches. This is where a short can occur as oxidation builds up between the aluminum wires, and poses a potential fire hazard. Updated devices with larger screws were created; however, these are not considered the best or only solution. Some people feel the aluminum should be removed and replaced with copper. There are some approved and accepted methods. Standard wire nuts are not approved for pig-tailing and, according to the Consumer Product Safety Commission, may be a greater fire hazard and should be repaired.

Approved methods according to the Consumer Product Safety Commission include:

• Copper pigtails crimped onto the aluminum at all receptacles and switches. A special tool is used for this application.
• UL-approved wire nut connectors, filled with anti-oxidant cream and designed specifically for aluminum-to-copper connections.
• Secure connections that are  on the approved Al/Cu devices.
• Use antioxidant on all aluminum wiring connections.

Monitor conditions such as flickering lights, voltage drop, or warm receptacles. In any case, an electrician familiar with aluminum wiring should be consulted to verify proper connections. Multi-stranded aluminum wiring is not part of this problem and of no concern. The majority of modern 220 amp rated houses are utilizing multi-stranded aluminum wiring.

COPPER CLAD ALUMINUM

Copper clad aluminum is easily mistaken for copper. It does not have the same problem with oxidation buildup as does aluminum. It is typically a #12 wire and still needs proper devices with the larger screw heads or approved pig-tailing methods. To identify copper clad aluminum, look for a silver color at the ends of the wires where they are connected to the grounding bar. Another location to identify copper clad aluminum is in the attic or crawlspace. In these areas, look for the identification on the wire sheathing such as CU Clad AL.

S. SHOWALTER, The Home Inspector's Guide to Training he Real Estate Professional, Aluminum (2d ed. 1998).