Many homeowners and home buyers tend to overreact when I tell them I found aluminum branch wiring in their home during the home inspection. They have this preconceived notion that the electrical system is not safe and the home is therefore dangerous. So I thought I would spend some time to discuss the history, issues, and solutions with respect to aluminum branch wiring.
Aluminum branch wiring was commonly used in residential homes in the late 1960’s through the mid-1970’s. Aluminum was less expensive and more readily available than copper. However, over time, issues developed that largely discontinued its use as a branch circuit wire.
A lot of this has to do with aluminums physical properties relative to copper. Aluminum has a greater resistance to electrical current (lower conductivity) than copper and thus requires a larger diameter wire to provide the same amount of current. It has a greater incompatibility when placed in contact with dissimilar metals, is more vulnerable to mechanical damage, and has a greater sensitivity to temperature change causing expansion and contraction.
The contacts on the receptacles, switches, fixtures, and circuit breakers were made of copper and over time the combination of expansion and contraction and the tendency of aluminum to oxidize when in contact with dissimilar metals caused the connections to become loose, arc, and create a potential fire hazard. Manufactures quickly realized that changes needed to be made.
Currently, there are two methods that are approved to make aluminum branch wiring safe. One method uses modified receptacles, switches, fixtures, and circuit breakers that have connecting terminals that are specifically made for aluminum wiring. These devices must be clearly labeled as CO/ALR or CU/AL from the manufacturer and are thus compatible with aluminum wiring. The other method involves adapting the aluminum wire using COPALUM connectors and #65 connectors. The COPALUM connector system attaches a copper wire to the old aluminum wires and is then crimped together using a high-compression power tool that achieves a “cold weld” between the conductors. Solid copper wire “pigtails” spliced to the aluminum wire this way may be connected to receptacles, switches, circuit breakers, lamps, appliances, and all other terminations in the normal manner. The #65 Twister Connection is a less expensive method that achieves the same copper “pigtails” without using an expensive power tool. While this method is also UL-approved, it is less reliable due to poorly-installed twist-on connectors installed by amateurs. Only a licensed electrician should be entrusted to perform electrical work.
If you have reason to suspect aluminum wiring at fixtures and receptacles, I recommend that an electrician test the electrical system. Aluminum wiring does not necessarily need to be replaced, but does require maintenance from a licensed electrician to prevent loose connections when in direct contact with dissimilar metals. Aluminum wiring still meets present day industry standards and local codes in specific limited applications, because in those applications it is still considered safe and adequate. Today, it’s mainly used for electrical service lines from the pole to your main electrical panel.