Aluminum wiring was commonly used in residential buildings during the 1960s and 1970s as a cost-effective alternative to copper wiring. However, it was soon discovered that aluminum wiring poses several problems that can affect the safety and functionality of the electrical system when used in the home’s branch circuits. The National Electric Code defines a general-purpose branch circuit as one that supplies two or more receptacles or outlets for lighting and appliances.
Some of the problems with branch aluminum wiring in residential buildings include:
1. Higher electrical resistance: Aluminum has a higher resistance to electricity than copper, which means it can generate more heat and potentially cause fires.
2. Oxidation: Aluminum is more susceptible to oxidation than copper, which can cause corrosion and further increase electrical resistance. Oxidation can occur more easily in areas with high humidity, such as bathrooms and basements.
3. Loosening of connections: Aluminum expands and contracts more than copper when it heats up and cools down. This can cause the connections to become loose over time, which can lead to arcing and potentially cause a fire.
4. Incompatibility with some devices: Aluminum wiring is not compatible with some types of devices, such as switches and outlets, which can lead to poor connections and further increase the risk of fires. This is especially true if aluminum and copper wires are connected together.
5. Difficulty in repair: Aluminum wiring is more difficult to repair than copper wiring, and may require special connectors and techniques to ensure proper installation.
For these reasons, many electrical experts recommend that homeowners with older aluminum wiring, in branch circuits, consider upgrading to copper wiring or installing special connectors designed for use with aluminum wiring.
There are some exceptions to this issue that the homeowner should be aware of.
1. Some wires may appear to be aluminum, but are, in fact, tinned copper. This wire can be identified by a cloth outer covering. Other than its age, there are no concerns with these wires.
2. Stranded, aluminum wires, are commonly used to feed the receptacle of a single appliance. Since there is no connection between aluminum and copper in these situations the opportunity for a galvanic reaction is avoided.
3. In recent years there has been the advent of solid (8000 series) aluminum wiring that is being used for appliance feeders.
For these and other reasons, it is important to have your home’s electrical system inspected evaluate, identify, and address any potential issues. Richard Katz and Katz Family Home Inspection can help you with this and all of your home inspection needs.