Ever since electricity was discovered and the first power grid installed, home’s have been wired for electricity.  In the early years, we had the infamous “knob-and-tube”, which consisted of single-stranded, unshielded and ungrounded wires.  Sometime around the 1950s, we were introduced to insulated ungrounded wires.  And not long after that, came what we generally use today in residential interior wiring, which is the grounded, insulated, “NM”-type cables.  These modern cables consist of a black insulated wire (hot), a white insulated wire (neutral) and a bare wire (ground), contained within an exterior protective sheathing.  Some wires also have an additional hot wire, which is red, used for double-pole (220V) circuits or split-circuits.  There are many more wire-types which I haven’t mentioned such as “AC” and “UF”, but we won’t go into these as they don’t pertain to this article.  Despite all these different types of wires, copper was always used as the conductor of choice, mainly due to its excellent conductivity, low resistance, and affordability/availability.  However, in the 1970s, this wasn’t quite the case.

In the early 1970s, copper prices were on the rise, and therefore the industry started switching to aluminum as the conductor of choice for residential electrical wiring.  Traditionally, copper had been more affordable than aluminum, however this was no longer the case.  Throughout the 70s, many homes were wired with aluminum wires, and all seemed fine.  However, problems started arising, which led the industry to switch back to copper in the mid-to-late 1970s.  “Hot-spots” were developing (outlets and switches were becoming warm to the touch), arcing/sparking was occurring, and other electrical problems were happening with the outlets, switches, and fixtures connected to aluminum wires.  The problem is related to a phenomenon known as galvanic corrosion.  See, when two different types of reactive metals come in contact, the metal with a higher electron affinity will “steal” electrons from the metal with a lower electron affinity.  This therefore leads to corrosion, similar in process to the oxidation of steel (rust).  So, because most fixtures, outlets and switches had copper contacts, the aluminum wires were corroding and therefore causing loose/poor connections.

Now, this may sound scary, and some people make it out to be worst than it is, but rest assured, it’s really not that bad.  However, insurance companies do not like it, and if you own or plan to purchase a home with aluminum wiring, you will probably have to have it modified in some way to qualify for insurance.  There are various options to modify your wiring, which range in complexity (and cost).  You can re-wire completely, however this is extreme to say the least, and definitely not necessary.  Another option is to change all your fixtures, outlets, and switches to ones designed strictly for aluminum wires (with aluminum contacts).  Although this is less extreme than a total re-wire, it can still be complex as aluminum fixtures can be hard to find.  By far the most common, and most recommended modification to aluminum wiring is something called “copper-tailing” or “pig-tailing”.

Copper-tailing (or pig-tailing) involves opening all the fixtures, outlets and switches, and adding a piece of copper wire to the ends of the aluminum wires.  These copper “tails” are attached to the aluminum wires with special wire nuts designed for aluminum to copper connections.  The other end of the copper tail is connected to the fixture.  Therefore, the wire that is physically connected to the fixture actually consists of copper, and not aluminum, and galvanic corrosion is therefore avoided.

Copper-tailing is a common, and relatively inexpensive process, which is acceptable by insurance companies.  So if your home has aluminum wiring, do not fret, as there is a simple solution.

Happy Home-owning!

Eric Parent