A homeowner can improve the safety of aluminum wiring in his house by retrofitting a dielectric wire nut on all the copper/aluminum connections in the house's light fixtures. These wire nuts, which have a special grease that prevents corrosion, must be approved for use with aluminum wire. The homeowner should also make sure that any replacement receptacles and switches are compatible with aluminum.
Between the early 1960s and the mid-1970s, aluminum was the preferred electrical wire in houses because it was less expensive than copper. However, aluminum wiring began to be implicated in a slew of house fires. Some experts believe that this was due more to bad wiring techniques than the aluminum itself, but aluminum does have intrinsic properties that make it a bit more challenging than copper.
Because aluminum wire has a greater resistance to electrical current than copper wire, it has to be larger to carry the same current. If a homeowner installs aluminum wire that's the same size as copper wire to carry the same current, this leads to overheating. Aluminum also contracts and expands more readily than copper, which can loosen the wire.
There's also the danger of the chemical reaction that occurs when one type of metal comes into contact with another, and aluminum wire was sometimes attached to steel connectors in some homes. Aluminum also oxidizes when it is exposed to the air, which causes the wires to corrode.