These photos are of an electrical system found in a house that my company, Magpie Property Inspections, conducted during a home inspection in Aurora Colorado. The home was built in the late 1960’s and initially had aluminum wiring installed in place of copper wiring. As the photos indicate, some renovations were conducted later which included mixing copper and aluminum wiring in the service panel and branch wiring.
Between 1965 and 1973, aluminum wiring was sometimes substituted for copper wiring in residential electrical systems. Connections in outlets, switches, and light fixtures with aluminum wiring may become increasingly dangerous as time passes. Poor connections cause wiring to spark and overheat, creating a potential fire hazard. If you have aluminum wiring in your home, it should be inspected by a qualified electrician experienced in evaluating and correcting aluminum wiring problems. Not all electrical contractors qualify. Aluminum wiring connections are subject to greater deterioration than is copper due to thermal expansion and contraction, vibration (caused when electric currents pass through wiring), oxidation (caused by exposure to oxygen in the air), and galvanic corrosion (caused when two different metals are connected together), all of which can cause poor connections. When wires are poorly connected they overheat, which creates a potential fire hazard.
There are safe remedies to correcting hazards from aluminum wiring. We recommend consulting with a qualified electrical contractor if your home was built during this time frame and you are concerned with having aluminum wiring in your electrical system.