At our afternoon inspection today, we came across a pretty rare find – solid aluminum branch circuit wiring. The term “branch circuit wiring” refers to the wiring that runs from breakers in the electrical panel to electrical devices throughout the home, such as outlets, switches, fixtures, etc. Solid aluminum branch circuit wiring has a known history of posing a potential fire hazard in homes, and we’ll review the primary issues here in case your home is a rare house that was wired with it.
Solid aluminum wiring was installed in a number of homes over the course of about a decade from the mid-1960s to the mid 70s. Some builders and electricians opted for aluminum over copper during this time period because of its lower cost, and the issues that are now known with solid aluminum were obviously not so well known then. But what, exactly, are those issues?
Aluminum wiring expands and contracts at a much higher rate than copper, and that slight movement causes pushing and loosening forces at connection points that can lead to loose connections. Once a connection is loose between a wire and screw, arcing and excess heat can occur that could ultimately lead to an unexpected fire hazard. Furthermore, since copper branch circuit wiring is far more common than aluminum, someone could join the two dissimilar metals and cause a reaction that leads to increased electrical resistance. In short, solid aluminum branch circuit wiring has “possible fire hazard” written all over it.
The term possible here is key, though. A home with solid aluminum wiring is not guaranteed to have a fire or other electrical defect at all, and the wiring in the home we inspected today has been present for over 50 years with tight connections (of those we checked) and no signs of overheating or other prior damage. Prior condition is not a sure indication of future performance, however, and the wiring in the home we inspected today could cause a hazard at any point in the future.
If you aren’t sure what type of branch circuit wiring exists in your home and you aren’t comfortable removing your electrical panel’s cover to check the wire ends at breaker connections, you can look at the wire sheathing right outside your panel or quickly pull an outlet (with caution, of course). The wire sheathing should contain writing that indicates it is aluminum, and the aluminum wire ends at outlet screws are easily identified by their silver color.
Be sure to not confuse any silver colored wiring with older tin cladded copper wiring that is typical of knob and tube in old houses. Distinguishing between the two is fortunately pretty easy, as solid aluminum will contain rubber sheathing that looks newer, whereas knob and tube will have more brittle, cloth based sheathing that is obviously old. Aluminum wire sheathing will likely also be lighter in color, and tin cladded copper sheathing will be dark.
If you do discover solid aluminum branch circuit wiring in your home, consult a qualified electrician to have it thoroughly evaluated – especially at connections. For complete peace of mind, strongly consider having it replaced with modern and safer non-metallic (NM) sheathed copper.
*For more information, visit our main website at http://www.hillinspections.com