page_title: Aluminum building wiring
section_title: Electrical device ratings
hierarchical_section_title: Aluminum building wiring / Problems / Electrical device ratings
caption_attribution_description: COALR Rated Devices
context_page_description: Aluminum building wiring is a type of electrical wiring for residential construction or houses that uses aluminum electrical conductors. Aluminum provides a better conductivity to weight ratio than copper, and therefore is also used for wiring power grids, including overhead power transmission lines and local power distribution lines, as well as for power wiring of some airplanes. Utility companies have used aluminum wire for electrical transmission in power grids since around the late 1800s to the early 1900s. It has cost and weight advantages over copper wires. Aluminum wire in power transmission and distribution applications is still the preferred material today.
  In North American residential construction, aluminum wire was used for wiring entire houses for a short time from the 1960s to the mid-1970s during a period of high copper prices. Electrical devices at the time were not designed with the particular properties of the aluminum wire being used in mind, and there were some issues related to the properties of the wire itself, making the installations with aluminum wire much more susceptible to problems.
context_section_description: Many electrical devices used in the 1960s had smaller plain steel terminal screws, which made the attachment of the aluminum wires being used at that time to these devices much more vulnerable to problems. In the late 1960s, a device specification known as CU/AL (meaning copper-aluminum) was created that specified standards for devices intended for use with aluminum wire.  Some of these devices used larger undercut screw terminals to more securely hold the wire.
  Unfortunately, CU/AL switches and receptacles failed to work well enough with aluminum wire, and a new specification called CO/ALR (meaning copper-aluminum, revised) was created.  These devices employ brass screw terminals that are designed to act as a similar metal to aluminum and to expand at a similar rate, and the screws have even deeper undercuts.  The CO/ALR rating is only available for standard light switches and receptacles; CU/AL is the standard connection marking for circuit breakers and larger equipment.
caption: Special CO/ALR rated wall outlet and wall switch
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