Purchasers or owners of homes built from the mid 1960’s until the late 1970’s with aluminum wiring are finding that many insurers will not provide or renew
insurance coverage on such properties unless the wiring is inspected and repaired or replaced as necessary and this work is inspected by ESA and a copy of the certificate of inspection is provided to the insurer. In some cases the insurer may require replacement of the aluminum wiring with copper wiring.
Check with your insurance company for their requirements.
In the mid-1960s when the price of copper spiked, aluminum wire was manufactured in sizes small enough to be used in homes. Aluminum wire requires a larger wire gauge than copper to carry the same current.
When first used in branch circuit wiring, aluminum wire was not installed any differently from copper. Typical connections from electrical wire to electrical devices, also called terminals, are usually made by wrapping the wire around screw terminals and tightening the screw. Over time, many of these terminations to aluminum wire began to fail due to improper connection techniques and dissimilar metals having different resistances and different coefficients of thermal expansion. These connection failures generated heat under electrical load and resulted in overheated connections.
In the late 1960s, a device specification known as CU/AL was created that specified standards for devices intended for use with aluminum wire. Because of more rigorous testing, larger undercut screw terminals were designed to hold the wire more suitably. 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 screw terminals that have even deeper undercuts and are designed to act as a similar metal to aluminum and to expand at a similar rate. CO/ALR applies only to standard light switches and receptacles; CU/AL is the standard marking for circuit breakers and larger equipment.
Joining aluminum and copper wires
Another issue is the joining of aluminum wire to copper wire. As aluminum and copper are dissimilar metals, galvanic corrosion can occur in the presence of an electrolyte and these connections can become unstable over time.
Special twist-on connectors have been designed for the purpose of joining aluminum to copper wires. These twist-on wire connectors use a special antioxidant paste to prevent corrosion of the connection.
"Pigtailing", which involves splicing a short length of copper wire (pigtail) to the original aluminum wire, and then attaching the copper wire to the existing electrical device. The splice of the copper pigtail to the existing aluminum wire can be done with special wire nuts, special crimp connectors, or special miniature lug-type connectors.
Please consult an electrician before preforming any of these applications.
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