What Is a Copper Clad Receptacle?

Aluminum Wiring

• A 1960s shortage in the supply of copper led manufacturers to use alternate materials to make wire. The use of aluminum wire, particularly where spurs to appliances and receptacles were spliced from heavier circuits, was common from the mid-1960s to the mid-1970s. The material was used both for general-purpose 15- and 20-amp receptacles and for heavy demand appliances, such as clothes dryers and ovens.

  Unfortunately, visual identification is difficult. Most aluminum wiring was sheathed in the same “Romex”-type plastic as its copper counterpart. Using a flashlight set at a parallel angle to the sheathing should reveal embossed “AL” markings on the plastic. Most sheathing featured printing that read “AL” or “Aluminum,” but the printing has a tendency to fade entirely away after several decades.

Copper-Clad Aluminum Wiring

• Because aluminum wiring does not conduct as well as copper, it generates more heat and therefore expands more during use. This exaggerated expansion and contraction was particularly problematic at the connections behind receptacles, where tightened-down screw heads are used to trap the wire in receivers. Aluminum wires had a tendency both to work loose and to fracture under the screws, both of which effects caused sparks. The connections made at those screw connections were prone to oxidization, also. The oxidization issue was addressed by applying copper cladding, a microscopic sheath of copper around the single-strand core of aluminum.

  Copper-clad aluminum can be identified by inspecting the stub ends at cut-offs. If the end of the wire appears silver, instead of a uniform copper color, it is copper-clad aluminum. The sheathing on such wire should be printed or embossed “CU Clad AL” or similar.

Dangers of Aluminum Wiring

• A national study into aluminum wiring, conducted for the U.S. Consumer Product Safety Commission by Franklin Research Institute, arrived at some startling conclusions. Their research found that “homes built before 1972, and wired with aluminum, are 55 times more likely to have one or more wire connections at outlets reach Fire Hazard Conditions than homes wired with copper.”

  The fire hazards were identified as occurring at connections to the wiring system, such as appliances, switches, junction boxes and receptacles. These issues were caused by deterioration in the aluminum wire at the connections as described above. The deterioration increased resistance at the connection, the resistance exacerbated the deterioration and the vicious cycle became incremental. As well as the sparking, the increase in resistance resulted directly in overheating at the connections when the appliance or receptacle was in use, and the overheating caused fires. According to the study, the mounting screws in receptacles could reach temperatures of 300 degrees F in normal use.

Copper-Clad Receptacles

• Copper-clad aluminum wiring was designed to mitigate the dangers of aluminum wiring by radically reducing the oxidization issues. Special receptacles were designed and produced that had larger receivers and larger screws to accommodate the expansion. These are identified by the marking “AL/Cu,” usually embossed on the reverse of the receptacle. The screws of such receptacles were made of a brass alloy intended to both further mitigate the oxidization issues and to expand and contract at the same rate as aluminum. An antioxidant compound was recommended for use with the dedicated receptacles.

Warnings of Failure Specific to Receptacles

• Warning signs are minimal before catastrophic failure. Typically the only indication that a receptacle-aluminum wiring interface is problematic is a heating of the receptacle faceplate during normal operation. A burning smell may be present before burning is noticed, and the appliance plugged into the receptacle may intermittently fail; this is most noticeable with flickering lights.