For electrical installations in buildings, copper is the material of choice because of its compactness and connectivity. Think of an installation with its switchboard, switches, sockets and lighting points, which require hundreds of connections made with a simple twist of a driver, yet remain in place for decades without problems.
Copper's compactness allows 1.5 or 2.5 mm2 wires for 15 or 20 A circuits, whereas aluminium would require bulkier 2.5 or 4 mm2 wiring. Such aluminium wire would be bigger, stiffer, and more difficult to bend or terminate, leading to larger switchboards, sockets, switches and lighting points. Moreover, aluminium reacts more readily to heat and forms an aluminium oxide layer, a ceramic insulator. To reduce this problem, tight contacts must be made, but aluminium easily flows under pressure. Therefore, special connectors need to be used, which makes installation components even bulkier.
Copper, on the other hand, has a conductive oxide and exhibits less creep. As a result, for final distribution circuits in buildings, only copper is currently used. Past US and Eastern European practices of using aluminium wiring have led to problems and have been abandoned. From 1965 to 1973, about 2 million homes in the US were wired with aluminium, leading to problems such as flickering lights, sockets not powered, overheated sockets, static on radios, sparks or arcing from outlets or switches, i.e. all symptoms of bad contacts. In Eastern Europe, aluminium wiring has lasted much longer due to shortages of copper in the Soviet economies.
Legacy use of aluminium wiring has remained a concern ever since. Meanwhile, aluminium wiring is no longer used in new buildings or renovations. For final distribution circuits below 10 mm2, IEC standards specify only copper wiring.
Besides copper's preventive function to ensure safety for building installations, copper also plays a role in fire safety services: copper's high melting point enables circuits to remain functional during a fire, e.g. to power emergency lighting or sprinkler pumps.
References
White Paper - Electrical Conductors: https://help.leonardo-energy.org/hc/en-us/articles/360025292593
Basec, July 2020: Aluminium cable conductors - the MUST know considerations you should be aware of
IEC 60228 - Conductors of insulated cables
Copper performs in electrical connections: https://help.leonardo-energy.org/hc/en-us/articles/207901015
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Last update: February 22, 2024
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