Aluminium Wire

Do you have Aluminium wire in your house?

This is a good question and one that comes up fairly often with home buyers and owners.  Aluminium wire was used in homes between the late 1960’s and 1978 (roughly).  There were almost 150 000 homes built in that time in Ottawa (according to the 2016 Census).  This is the most prolific home building period in Ottawa with nothing even coming close before or since.  Chances are if your home was built in that almost 20 year period, it was wired with Aluminium.

Why did builders stop using Aluminium wire?

These wires have a higher co-efficient of thermal expansion than copper.  This is to say that Aluminium heats up (as all wire does when electricity runs through it) and expands more than copper and that leads to the wire trying to move out from where it is attached.  The phenomenon is called “creep” and can lead to poor connections and subsequent overheating.  This can happen in the electrical panel, switches and outlets.  The second problem with aluminium is that it is softer then copper and electricians may have nicked the wiring inadvertently.  Nicking the wire reduces the diameter and its ability to carry electricity safely.  Thirdly, the oxide of aluminium that forms on the wire is a very poor conductor.  The greenish oxide that forms on copper wiring does not result in a problem but oxide that forms on aluminium corrodes.  This can lead to higher resistance and temperatures.

What can be done about Aluminium wiring?

Because of the above difficulties with Aluminium, special components were produced.  They are designated Cu-Al and include wire connectors (or wire nuts), electrical receptacles, circuit breakers and stove blocks.  Electrical outlets should be replaced with those designated CO/ALR.

As long as proper connectors are used and the connections are made without damaging the wire, aluminium wiring is considered safe.

Is Aluminium wiring a “deal breaker” when you are buying a house?

While not “ideal”, Aluminium wiring should not disqualify a home if that home is otherwise what you are looking for.  The provision of the special connectors is not an expensive undertaking and is worthwhile.  Where there is only a small amount of Aluminium wiring, it is often easier to replace it with copper wire especially if the service panel would have to be replaced.

How do I inspect your home for Aluminium wiring?

This is part of a standard inspection.  There are a number of steps in detecting Aluminium wires.

  1. When was your home built?  If it was between 1960 and 1980, chances are you have Aluminium.
  2. Look at the distribution panel.  I check the wires leading to the wire nuts.
  3. If there is Aluminium, I look to see that the panel and wire nuts are properly rated as well as check to see that anti-oxidant gel is used.
  4. I will inspect a representative number of outlets and switches, checking the outlets and switches are rated for Aluminium.

Posted by Jeremy Scratch

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