Aluminum Wiring

Most electrical wiring in modern homes is copper, except for some high-amp circuits such as electrical ranges or air conditioners. But some houses built or remodelled between the early 1950s and late 1970s were wired with aluminium.  It’s easy to identify because the word ALUMINUM or the letters AL are stamped on the plastic covering or cable (but don’t confuse the name ALCAN with aluminium wiring because the company makes both aluminium and copper wiring for homes). 

Aluminium wiring is incompatible with fittings designed for copper only.  Improper connections may cause electrical resistance leading to overheating or fire.  Aluminium wiring must be “pigtailed” with copper wiring using proper connectors (Marrette, which are brown; or Ideal, which are purple).

Aluminium wiring is of concern because it has a tendency to oxidize and to expand, creeping off receptacle terminal screws.  It is also softer than copper and therefore easily nicked.

Unsafe Warning Signs

• Usually warm or warped outlets and switch cover plates
• Smoke or sparks coming from receptacles and switches
• Strange odours in the area of receptacles and switches
• Untraceable problems with plug in lights and appliances
• Periodic flicking of lights when appliances like refrigerators start up
  

* An excerpt from Pillar to Post Home Information Series. Contact your local home inspector for a full version.