Copper vs. Aluminium Conductors

Copper conductors

Electrical devices often contain copper conductors because of their multiple beneficial properties, including their high electrical conductivity, tensile strength, ductility, corrosion resistance, thermal conductivity, resistance to electrical overloads, compatibility with electrical insulators and ease of installation.

Despite competition from other materials, copper remains the preferred electrical conductor in nearly all categories of electrical wiring. For example, copper is used to conduct electricity in high, medium and low voltage power networks, including power generation, power transmission, power distribution, telecommunications, electronics circuitry, transformers and countless other types of electrical equipment

Aluminium conductors

Aluminium wire was common in South African residential wiring from the late 1960s to mid 1970s due to the rising cost of copper.  Because of its greater resistivity, aluminium wiring requires larger conductors than copper.  For instance, instead of a 50mm copper wire for most underground LV extensions, aluminium wiring would be 95mm on a typical 170 ampere circuit.

Aluminium conductors were originally indiscriminately used with wiring devices intended for copper conductors. This practice was found to cause defective connections unless the aluminium was one of a special alloy for breakers, switches, receptacles and splice connectors, were specially designed for the purpose.  These special designs address problems with junctions between dissimilar metals, oxidation on metal surfaces, and mechanical effects that occur as different metals expand at different rates with increases in temperature.

Unlike copper, aluminium has a tendency to creep (deformation)  under pressure, so screw clamped connections may get loose over time.  This can be mitigated by using spring-loaded connectors that apply constant pressure, applying high pressure cold joints in splices and termination fittings.

Also unlike copper, aluminium forms an insulating oxide layer on the surface.  This is sometimes addressed by coating aluminium wires with an antioxidant paste at joints, or by applying a mechanical termination designed to break through the oxide layer during installation.

Because of improper design and installation, some junctions to wiring devices would overheat under heavy current load, and cause fires.  Revised standards for wiring devices (such as the ”’CO/ALR”’ “copper-aluminium-revised” designation) were developed to reduce these problems.  Nonetheless, aluminium wiring for residential use has acquired a poor reputation and has fallen out of favour.

Aluminium conductors are still used for bulk power distribution and large feeder circuits, because they cost less than copper wiring, and weigh less, especially in the large sizes needed for heavy current loads. Aluminium conductors are most commonly installed in rural, agricultural areas and industrial sectors, where one of the biggest advantages is minimum theft compared to copper conductors. Office Park, Fourways, Gauteng+27 11 465 6947