Aluminum Wiring is Dangerous
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Aluminum Wiring is Dangerous

Aluminum wire was used to wire new homes from the late 1960s through the early 1970s. This was a time when the cost of Copper was at an all time high and home builders, electricians, and home buyers were looking for a way to save money on electrical. Besides being less expensive, aluminum had other appealing characteristics. For one thing it had a much higher conductivity to weight ratio than copper wire did. Conductivity, for those of you who may have forgotten what you learned in high school physics class, is a measure of how easily a material conducts electricity. Because of the higher conductivity to weight ratio, the utility company were already using aluminum wire in their power grids, electricians saw no reason not to use it in wiring homes. Since that period of time, numerous house fires have been traced to aluminum wiring and most local Authorities Having Jurisdiction (AHJ), the local Building Permits and Inspections Departments, no longer permit it to be used in new home construction.

A Franklin Research Institute conducted a nationwide survey for the United States Product Safety Commission (CPSC) of homes built before 1972 that had branch circuits wired with aluminum electrical wire. The results were shocking, if you will forgive my play on words. Homes built prior to 1972 and wired with aluminum wire were fifty-five times more likely to develop “Fire Hazard Conditions” in one or more locations where those conductor terminated on a device, such as an electrical receptacle, light switch, circuit breaker, light fixture, etc. Why was that? What was the problem with using aluminum wiring in homes that led to these potential fire hazards? Why was it OK for use in the utility company's power grids but OK for residential wiring?

Cold Creep” sets in.

The number one cause of all these problem was a phenomenon known as “Cold Creep.” Aluminum, like copper or any other metal, expands and contracts cyclically as it heats up and cools down. However, unlike copper and most other metals, aluminum starts to loose its tightness after a few thermal cycles. This causes wires terminated on switches and receptacles to come loose at their terminal screws.

Oxidation sets in.

As you may recall from your high schools physics and chemistry classes, a chemical reactions takes place when two dissimilar metals come into close contact with one another, such as when the aluminum wire comes into contact with the brass terminal screws. This chemical reaction causes oxidation to form on the wire. The oxidation causes a high resistance connection and a voltage drop takes place between the wire and terminal. This causes heat to develop which further exacerbates that being developed by the already loose connections. When enough heat develops, the surrounding structural material ignites.

Switches, receptacles, and other devices were not designed for use with aluminum wire.

Today's quality devices are rated for use with both aluminum and copper wire and stamped with “AL/CU,” or with “CO/ALR.” The “CO/ALR” rating supersedes the “AL/CU” rating, but both are safe for use with aluminum wiring. Back in those early days, electrical devices were not constructed of material compatible with both aluminum and copper wire.

What to do if you suspect that your home is wired with aluminum wire.

The first thing to not do is panic. Aluminum wiring that was properly installed is perfectly safe. The operative words here are “properly installed.” What you need to do, if you are really comfortable working with electricity, is to perform a thorough inspection of your home's electrical system. If you are not totally comfortable working with electricity, then hire a qualified electrician or an electrical inspector to perform the inspection for you.

How to identify aluminum wiring.

Almost all aluminum wiring was installed as nonmetallic sheathed cable, Type NM cable, also known in the trade as “Romex”. That is the same plastic sheathed cable that we use today except the conductors were made of aluminum instead of copper. If the Romex cable contains aluminum conductors there will be an “AL Conductors” embossed on the plastic jacket along with other information about the cable. If your home is wired with aluminum wire, you will need to make a closer inspection of all the places where the wire terminates on some device.

What to look for.

CAUTION: Turn off the circuit breaker controlling the branch circuit that you are inspecting.

  • Drop ceiling mounted light fixtures and ceiling fans and check to see if they are stamped with “AL/CU” or “CO/ALR”. If they are not so stamped they were not designed to be used with aluminum wire. If the light fixtures or ceiling fans that you have are not rated for use with aluminum wire, you have two choices, you can replace the fan or light fixture with one rated for use with aluminum wire or you can use a COPALUM Pigtail splice between the fixture wires and the aluminum circuit wires. Using a COPALUM Pigtail splice takes special tools and is beyond the scope of this article.

  • At receptacles and switches, check to see if they are stamped with the “AL/CU” or “CO/ALR” markings. If not replace them with ones that are designed for use with aluminum wiring. Replacing the switches and receptacles will be quicker and cheaper than using the COPALUM Pigtail splices. Check to make sure the wires are looped at least ¾ of the way around the terminal screws and make sure that the screws are tight. Never, ever use the back-wiring push-in terminals with aluminum wire.

  • Check to make sure that there are no signs of over heating—charred or burned insulation, melted insulation, discolored devices or device cover plates. Switches and receptacles that are warm to the touch is a definite indication that you have a problem that requires immediate attention.

  • Do not forget to check the wiring inside the service panel.

I will cover working aluminum wiring in future article.


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Comments (4)

Yikes good info, scary picture too!

I believe, pretty much anything made up of aluminium is dangerous. I always thought they discontinued the use of it especially in cooking utensils.

Learned shocking precaution here, thanks Jerry.

Wow, this is truly alarming. We have some aluminum wires here in my locality. Good sharing.