Shortly after aluminium wiring became popular(about 1960, due to the fact that the copper had become much more expensive than Al wires), some problems started to appear. These included flickering lights, warm cover plates on switches and receptacles, and burned insulation on wiring. There was an overheating issue, and overheating can mean fires. They looked into it and found there were three other differences between copper and aluminium.
- Softness: Aluminium is a much softer metal than copper. Electricians who had always worked with copper found that it was very easy to nick, cut, or crush the aluminium wiring when removing insulation or making connections. They had to be gentler. Damaged wire creates local hot spots and results in overheating.
- Creeping: When electricity flows through wire, the wire heats up. Aluminium wire expands more than copper when it heats up. The repeated expansion and contraction as the wire heated up and cooled down caused to the wire to creep out from under the terminal screws that held the wire in place. This wire creeping resulted in loose connections and overheating.
- Rusting: When metals rust, they form an oxide on the surface. Rust on steel is red, rust on copper is green, and rust on aluminium is white. It’s not a big problem when copper wiring rusts, since the copper oxide that forms is electrically conductive. It doesn’t interfere with the wire’s ability to do its job. When aluminium wiring rusts, the white oxide is not a very good electrical conductor. It does interfere with the flow of electricity, and again, can cause overheating.
The problem was at connections, such as receptacles, switches, light fixtures, appliance connections, and at the panel. The solution was special connectors.
Connectors that work well with both copper and aluminium were created. That included:
- Small receptacles marked CO/ALR or AL-CU
- Large receptacles (> 20 amps) marked AL-CU or CU-AL
- Switches marked CO/ALR
- Twist-on wire connectors (sometimes called wire nuts) marked AL-CU or CU-AL
Electrical panels and breakers marked AL-CU or CU-AL were also available.
There were other approved connection systems that have come and substantially gone.
House Depot offers solutions to make your home a safe environment with some cost effective choices. We will deal with everything including E.S.A inspection and documentation for your home insurance.