In April 1974, two people were killed in a house fire in Hampton Bays, New York. Fire officials determined that the fire was caused by a faulty aluminum wire connection at an outlet. According to the Consumer Product Safety Commission (CPSC), “Homes wired with aluminum wire manufactured before 1972 [‘old technology’ aluminum wire] are 55 times more likely to have one or more connections reach fire hazard conditions than is a home wired with copper.
Aluminum Wiring – Penney Electric/ C10 Lic # 1014853 (penneyelectricinc.com)
Many may remember the copper craze of the 1970s where the cost of copper became prohibitive in residential home building. The solution: they started using aluminum wires for residential home electrical wiring with horrific results. It took a few years but the rules were changed either by the Underwriters Laboratories or the NEC or maybe both. The author is unclear on the exact process that happened except that there were house fires as a result of using aluminum to wire residential homes.
What Was the Cause?
But what was the cause? What was it about aluminum in residential homes that caused fires and therefore loss of life? The answer may surprise you.
- Aluminum has less conductivity than copper but all that one does to counter that is use larger aluminum wires. That was not the issue.
- Aluminum has quite a bit less tensile strength than copper but once a string of wiring is installed, there is nothing to pull on it so that should not be an issue.
- Aluminum responds much more than copper to vibration. Given a vibration environment such as a motor vehicle, aluminum will develop micro-breaks which drives its resistance up over time and use. But even if a home is in an earthquake zone it only happens once every few years at most so scratch that problem.
- Oxides form almost instantly on aluminum making soldering or welding nearly impossible except under industrial conditions. But soldering is not used in residential house wiring. What else could go wrong?
- You can’t let aluminum touch another type of metal such as copper or iron. That would facilitate a galvanic cell and corrosion. But the same is true for copper so what gives?
The Problem
The problem was the homeowner and maintenance. For varied reasons, a homeowner would put in an additional receptacle or change an existing one or make some other change to a circuit. You need to use compatible connectors when changing things for aluminum circuits. The homeowners did not always follow this rule and their homes burned to the ground. When dissimilar metals are put in contact there is a galvanic discharge which becomes corrosion. Corrosion increases resistance. Increased resistance increases temperature with the flow of electricity and in some cases, there was spontaneous combustion. That was not cool.
What About My Car?
The automotive industry has been migrating to aluminum wiring. Does that sound dumb in view of what homeowners experienced in the 1980s? When you review the list above but with reference to a motor vehicle instead of a residential home, you might find yourself raising your eyebrow.
Alloyed Aluminum
There have been technical advances made in metallurgy and aluminum.
Conductivity has not improved but this can be countered by wire sizing.
Tensile strength is a very great problem. Copper has a tensile strength of about 220 MPa (mega-Pascals). Industrial-grade aluminum, however, has less than only 150 MPa. The list goes on.
Here is a paper published by Sumitomo Electric showing the results of their development for alloyed aluminum making it a suitable replacement for copper.
Aluminum wiring has been in use in the automotive industry for a couple of years in some vehicles. Most notably, the Tesla.
Why Bother
The advantages of aluminum for the automotive industry are too great to ignore. The Sumitomo alloyed aluminum saves over 50% on weight. That is HUGE. There is a cost savings as well. But also consider that copper is subject to scarcity of supply (such as at the time of this writing). But there are some unexpected beneficial aspects. Most notably, the wire bend radius is improved over copper.
Rest assured, aluminum is in your future car’s future.
