I occasionally run into homes wired with solid core aluminum wire. This of course scares many people who have heard about the dangers associated with this type of wiring. Like many of these kinds of issues the rhetoric often exceeds the value of the argument. However, I found an interesting article from a home inspection site that I have added here in its entirety. It's a good read if you have concerns about this type of wiring.
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Dispelling the Myths
We hear regularly that aluminum wiring has been recalled and that it is no longer approved or permitted in homes—neither of these is true. Aluminum wiring is permitted with the appropriate installation methods and materials.
Electrical wiring in homes has traditionally been copper since the introduction of electricity in homes in the late 19th century. Aluminum wiring was introduced to homes in North America in the mid-1960s. The price of copper was very high, and aluminum was a cost-effective alternative.
Not as Good as Copper
Was aluminum as good as copper? Not quite. It was recognized from the beginning that copper is a better conductor of electricity. The manufacturers and the authorities adjusted for that by using slightly larger aluminum wire to perform the same work as copper. Most branch circuit wiring in homes is 14 gauge copper. The equivalent aluminum wire is 12 gauge. Remember, though: 12 gauge is larger than 14!
The installation methods were exactly the same for aluminum as for copper.
Shortly after aluminum wiring became popular, 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 aluminum.
Softness: Aluminum 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 aluminum 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. Aluminum 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 aluminum 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 aluminum 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 aluminum 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.
In Part Two of this post, we explore a few more additional considerations, as well as questions about insurance, and what to do if you have aluminum wiring in your home.
In Part One, we took a look at the difference between copper and aluminum wiring, the initial issues with aluminum wiring, and how inspectors can benefit from home inspector training to fully understand issues like this to better serve their clients. In this part, we will continue by looking at the requirements for aluminum wiring, a little bit of its history, insurance information, and what to do if you have aluminum wiring in your home.
First, let’s take a look at a few of the requirements put in place for aluminum wiring.
Push-In Not Allowed
The authorities found that aluminum performs better with screw type connections, where the wire was looped around a screw and held in place by the head of the screw, rather than with the “push-in” type terminations on some devices, sometimes referred to as ‘quick wire’, ‘dagger’, or ‘bayonet’ terminations. Push-in type terminations are not permitted with aluminum wiring.
Joint Compound/Anti-Oxidant Grease
Stranded aluminum wires need a special joint compound that is electrically conductive and prevents rust. The stranded conductors are used on larger cables (8 gauge and up), typically used for large appliances like stoves and ovens. It is agreed that joint compound is a good practice on all aluminum wiring, but the compound is generally not required on solid conductors.
A Better Alloy
In the early 1970s, the alloy used for aluminum wiring was changed to a superior quality wire much better suited to use for electrical work.
The Irony of Improvement
These changes improved the performance of aluminum wiring significantly. However, by the time the aluminum wiring issues were identified and improved, aluminum had received enough bad publicity that it became unmarketable. By the late 1970s, it was no longer used by most builders, although it is still approved and less expensive than copper. Most manufacturers have stopped making solid strand aluminum conductors, although multi-strand conductors for larger appliances and service entrances are still widely used.
The Insurance Question
The home insurance world became aware of the issues around aluminum wiring, and some insurance companies refuse to insure homes with aluminum. Others require a certificate from a licensed electrician or the electrical authority. Some say these decisions were made on conservative underwriting criteria rather than actual loss experience.
Is a Retrofit or Replacement Required?
There were a lot of homes built with aluminum wiring, and a lot of older homes that were updated with aluminum during the 1960s and 70s. What about all these homes that still have aluminum wiring? The electrical authority in Ontario, Canada says, “Aluminum wiring itself is safe and if proper connections and terminations are made without damaging the wire and using approved materials installed in accordance with the Ontario Electrical Safety Code and the manufacturer’s instructions, there should be no problems with the aluminum wiring installation.”
Home inspectors who identify aluminum wiring in homes should look for evidence of problems including flickering lights, warm cover plates, discolouration, and melted insulation. Inspectors should recommend an electrical audit of all the connections in the home performed by specialists. The authority in our area does not require that devices be replaced with aluminum-approved devices if no problems are identified.
Homeowners who have aluminum wiring should have an electrical audit performed to ensure their home is safe.
Aluminum wiring in homes has had problems, and significant improvements have been made. Neither authorities nor electrical specialists recommend rewiring a house with aluminum. All connections should be inspected and replaced or improved as necessary—there is no evidence that suggests this has to be done on a regular basis.