Aluminum wiring was used in homes in the 1960s as a cheaper alternative to copper, but it can be dangerous if installed incorrectly. The main problem is “cold creep,” which causes the wiring to loosen over time. Aluminum also oxidizes, leading to corrosion at connection sites. While aluminum wiring can be safe if installed correctly, it has been phased out in favor of copper due to its potential danger. Homeowners insurance companies may charge higher premiums for homes wired with aluminum.
It is generally accepted that the best quality metal to use in home wiring is copper, although aluminum can also be used. Aluminum wiring is commonly used to transmit electricity across power grids. This is because it is lighter and usually cheaper than copper. For some time, starting in the 1960s, aluminum wiring was used in homes as a replacement for copper wire in new construction. This has led to some of the typical problems with aluminum wiring when installed incorrectly, such as overheating which can lead to fires.
The most significant problem with aluminum wiring is referred to as cold creep. As metal heats up, it expands and then contracts again when it cools. This can be dangerous in the time the electrical connections are made. If it undergoes sufficient heating and cooling cycles, caused by daily use, the aluminum wiring will gradually loosen at the connection point. To make matters worse, aluminum oxidizes over time, sometimes causing more heat to build up at the connection, which causes greater electrical resistance, which in turn produces more heat.
This is not to say that aluminum wiring is inherently dangerous. When installed correctly, aluminum wiring can be as safe and effective as copper. However, it also tends to be unforgiving of poor or careless workmanship. Some home fires have been caused by faulty connections with aluminum wires, including some where people have been killed. In nearly all cases, poorly connected wires were responsible for the fire, suggesting that even if the wiring had been done with copper, the fire could still have occurred.
Due to the potential danger posed by aluminum wire, it was phased out as a home wiring material in favor of copper. In addition to overheating, aluminum also has other minor problems. Oxidation is the primary one, which occurs when aluminum oxide builds up on the surface of the aluminum wiring. This is the equivalent of rust, but on aluminum rather than iron or steel, and is an electrical insulator, meaning it doesn’t conduct electricity. This problem is worse at the connection sites and the aluminum oxide may need to be cleaned from these connections if repairs need to be made.
Oxidation has little practical implications other than the corrosion that can occur at connection sites due to it. Another important point about aluminum is that, even under the best of circumstances, it doesn’t conduct electricity like copper. This results in larger diameter wires as well as a slightly higher risk of overheating away from the connections as well. For all of these reasons, aluminum wiring is no longer used in homes, and some homeowners insurance companies even charge customers higher premiums if their homes are wired with aluminum, due to the higher perceived risk.
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