Some older homes built in 1965 to 1973 had aluminum wire installed due to the high cost of copper at the time. After more than a decade of use defects in aluminum wiring were discovered and eventually aluminum was no longer used in residential branch wiring. Aluminum was found to have inherent weaknesses that could possibily lead to overheating or fire.
Aluminum wiring is much softer than standard copper wiring. This means that it is susceptable to being broken, cut, and damaged which can leave live electrical wires exposed. Another problem is that when aluminum corrodes, it is not as conductive as copper. Copper that corrodes can remain conductive and continue its flow of power. However with aluminum wiring, corrosion in wiring will impede the flow of electricity and can cause a number of other issues. Aluminum also expands and contracts when it becomes hot.
Aluminum has a high resistance to electrical current flow, which means that given the same amperage, aluminum conductors will have to be a larger diameter than would be required by copper conductors. Your typical residential branch circuit in copper is 14-2 wire, aluminum branch circuit is required to be 12-2 one wire size higher.
Exposure to oxygen in the air causes deterioration to the outer surface of the wire. Aluminum wire is more easily oxidized than copper wire, and the compound formed by this process – aluminum oxide – is less conductive than copper oxide. Most electricians will use an anti-oxidizing paste on any aluminum wiring they install.
Is Aluminum Wiring Dangerous?
When connections between aluminum wires and their unprotected connections to outlets and switches deteriorate, they become a fire hazard. As electrical resistance builds up inside the wire, the wire gets hotter and hotter at points of resistance. The point of connection can eventually become so dangerously hot that it can ignite the material around it. In some cases, electricity in the wire may even arc as it attempts to contact the connected device.
The Canadian Standards Association says that aluminum wiring in houses manufactured prior to 1972 are 55 times more likely to have a connection reach fire hazard conditions, compared to copper. So not only are you at higher risk of fire but, due to the increased fire risk, you may have a hard time finding an insurance company to provide you with home insurance. The main danger with this wiring is in the connections. When electricity passes through electrical cables and connectors, the wires expand and heat up. One of the issues with this type of wiring is that it expands three times more than copper does.
FIXING THE PROBLEM
Aluminum wiring can be replaced or repaired to effectively and permanently reduce the possibility of fire and injury due to failing (overheating) wire connections and splices. It is highly recommended that you hire a qualified electrician to perform this remediation.
Three Accepted Methods of Repair
1) Complete Replacement of Copper Cable
AlumiConn is a lug style connector with three separate ports to eliminate intermixing of conductors. It coats aluminum wires with a thin layer of silicone sealant to provide resistance from oxidation, and uses set screws to break up surface oxides and provide a secure mechanical connection.
3) Acceptable Alternative Repair Method/AlumiConn Connector
If you have aluminum wiring in your home it is recommended that you have it inspected by a Licensed ESA Electrician. Many Insurance companies will not insure a home with aluminum wiring. Only when the complete electrical system has been inspected can you know if your home is safe. In order for your home to be truly safe every aluminum connection has to be inspected and repaired using approved methods.
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