Although banned for the most part, it should be pointed out that there are a few situations where its use was still approved. This generally applies to circuits that are dedicated to a single purpose.
This could be service entrance wiring, electric range circuitry, and 240 V HVAC circuits, as a few common examples.
Why was it Allowed in the First Place?
The main reasons the substituted for copper is that it is less expensive than copper and because it had not been outlawed yet although the danger signs were certainly there. There are always some contractors willing to cut corners financially.
Anyone contemplating purchasing a house with this wiring needs to be aware of this issue. Why? Not only does it put occupants in danger, but some insurance companies will charge elevated homeowners insurance policy rates or even refuse coverage.
Aluminum Wiring Poses a Fire Hazard
This cheaper metal poses such a fire hazard because it will expand. Naturally, this compromises the insulating layer and can cause connection screws to loosen up over the course of time.
In fact, aluminum has a coefficient of expansion in inches per degree Fahrenheit of 0.0000123 – 0.0000129. Copper’s rating is much lower at just 0.0000093. A difference that large is certainly reason for concern.
A secondary issue is an inherent incompatibility between aluminum and the various metals used in connections, junction boxes, electric switches, etc. This will induce a situation known as micro-fretting.
What is this? A surface oxide forms which has been know to cause arcing and overheating. Inspectapedia.com tells us, “The connections can become hot enough to start a fire without ever tripping a circuit breaker.”
Furthermore, the U.S. Consumer Product Safety Commission (CPSC) has this take on it, “homes wired with aluminum wire manufactured before 1972 are 55 times more likely to have one or more connections that reach ’Fire Hazard Conditions’ than are homes wired with copper.”
Tips to Arouse Your Suspicions
Any repair or opening of electrical circuits should be done by a competent person, notably a licensed electrician when the local electrical building code requires it.
There are many indicators other than just knowing that your house was built in the mid-60s to the early 70s. The CPSC recommends checking for warm electrical switchs or receptacle face plates. Watch for lights that flicker when an incandescent bulb is still in a good condition. Another scary clue is when you can smell melting or burning plastic.
At times it is simple to identify just by seeing the word aluminum written on the insulation or sheathing. Also, look is in your circuit breaker box where the sheathing is stripped away to make the electrical connection.
You might also go around the house, remove face plates, and once again, examine the bare, stripped wiring where it makes a connection.
Finally, if all of your wiring is 12-gauge and you can’t find any 14-gauge, this is a strong indicator. Why? Because if aluminum is utilized, the old building code said that it must be one gauge larger than copper. This one is no guarantee but is a strong indication. The gauge should by embossed on the sheathing.
