Electrical wiring: Difference between revisions

The [[German Commission for Electrotechnical, Electronic, and Information Technologies of DIN and VDE]] (DKE) (Deutsche Kommission Elektrotechnik Elektronik Informationstechnik in [[DIN]] und [[Verband der Elektrotechnik, Elektronik und Informationstechnik|VDE]]) is the organisation responsible for the promulgation of electrical standards and safety specifications. DIN VDE 0100 is the German wiring regulations document harmonised with IEC 60364. In Germany, blue can also mean phase or switched phase.

The [[United Kingdom]] requires the use of wire covered with green/yellow striped insulation, for safety earthing (grounding) connections.<ref>{{cite book |title=NEC Q and A: Questions and Answers on the National Electrical Code |author=Noel Williams, Jeffrey S. Sargen |year=2007 |url=https://books.google.com/books?id=fBkUkF2ZRU4C&q=electrical+codes+require+green+with+yellow+stripe&pg=PA117 |page=117 |publisher=Jones & Bartlett Learning |isbn=9780763744731 |access-date=4 January 2016}}</ref> This growing international standard was adopted for its distinctive appearance, to reduce the likelihood of dangerous confusion of safety earthing (grounding) wires with other electrical functions, especially by persons affected by red–green [[colour blindness]].

In the United States, colour-coding of three-phase system conductors follows a de facto standard, wherein black, red, and blue are used for three-phase 120/208-volt systems, and brown, orange or violet, and yellow are used in 277/480-volt systems. (Violet avoids conflict with the NEC's high-leg delta rule.) In buildings with multiple voltage systems, the grounded conductors (neutrals) of both systems are required to be separately identified and made distinguishable to avoid cross-system connections. Most often, 120/208-volt systems use white insulation, while 277/480-volt systems use grey insulation, although this particular colour code is not currently an explicit requirement of the NEC.<ref>{{cite web |title=Color Coding Chart |url=https://www.conwire.com/about/technical-info/ |publisher=Conwire |access-date=4 January 2016}}</ref> Some local jurisdictions do specify required colorcolour coding in their local building codes, however.

|+ Standard{{efn|The colors in this table represent the most common and preferred standard colors for wiring; however others may be in use, especially in older installations.}} wire insulation colorscolours for alternating current

| [[File:Color wire brown.svg|80px|Brown]] [[File:Color wire black.svg|80px|Black]] [[File:Color wire grey.svg|Grey|80px]]<ref>Switzerland before 2005 also red and white for phases.</ref>'''Prohibited:''' [[File:Color wire green yellow prohibited.svg|80px|Green/Yellow]]

[[File:Color wire blue.svg|80px|Dark Blue]]<ref>Switzerland blue or light&nbsp;blue for neutral conductors</ref>

<br>[[File:Color wire white.svg|80px|White]] ''usually'' used for "Switched Line" <ref>{{cite book |date=2007 |title=AS/NZS 3000 "Wiring Rules", Table 3.4, CONDUCTOR COLOURS FOR INSTALLATION WIRING, "Function: Active: Any colour other than green, yellow, green/yellow, black or light blue."|no-pp=y}}</ref>

[[File:Color wire light blue.svg|80px|Light Blue]]{{efn|name=nzblack|ExceptUse thatof inlight blue for Neutral may cause confusion with dark blue for L3. In New Zealand domestic installations, the only permitted color for Neutral is Blackblack.}}

| '''Prohibited:''' [[File:Color wire green yellow.svg|80px|Yellow]] [[File:Color wire green.svg|80px|Green]] [[File:Color wire black.svg|80px|Black]]<br>To designate any phase, the abovebelow colorscolours are '''prohibited'''.:

In North American practice, for residential and light commercial buildings fed with a single-phase [[Split-phase electric power|split 120/240 service]], an overhead cable from a transformer on a [[Utility pole|power pole]] is run to the service entrance point. The cable is a three conductor twisted "triplex" cable with a bare neutral and two insulated conductors, with no overall cable jacket. <ref>{{cite web |url=https://science.howstuffworks.com/environmental/energy/power7.htm |title=Generating Power to Your House - How Power Grids Work - HowStuffWorks |work=HowStuffWorks |date=April 2000 |access-date=21 February 2016}}</ref> The neutral conductor is often a supporting "messenger" steel wire, which is used to support the insulated line conductors.

Solid aluminium conductors were originally made in the 1960s from a utility-grade aluminium alloy that had undesirable properties for a building wire, and were used with wiring devices intended for copper conductors.<ref name=NEMA>{{cite web |url=http://www.stabiloy.com/NR/rdonlyres/2AFAE0AC-850A-44C9-A3C2-C54128AE1415/0/NEMAWhitepaperEvolutionofAluminiumConductors.pdf |title=The Evolution of Aluminum Conductors Used for Building Wire and Cable |work=NEMA |date=2012 |access-date=12 October 2016 |archive-date=10 October 2016 |archive-url=https://web.archive.org/web/20161010044452/http://www.stabiloy.com/NR/rdonlyres/2AFAE0AC-850A-44C9-A3C2-C54128AE1415/0/NEMAWhitepaperEvolutionofAluminiumConductors.pdf |url-status=dead }}</ref><ref name=IAEI-Article>{{cite web |url=http://www.aluminum.org/sites/default/files/Aluminum%20Building%20Wire%20Installation%20%26%20Terminations.pdf |title=Aluminum Building Wire Installation & Terminations |work=IAEI News (January/February 2006) |access-date=12 October 2016 |archive-date=27 January 2021 |archive-url=https://web.archive.org/web/20210127230846/https://www.aluminum.org/sites/default/files/Aluminum%20Building%20Wire%20Installation%20%26%20Terminations.pdf |url-status=dead }}</ref> These practices were found to cause defective connections and fire hazards. In the early 1970s new aluminium wire made from one of several special alloys was introduced, and all devices – breakers, switches, receptacles, [[splice connector]]s, [[wire nut]]s, etc. — were specially designed for the purpose. These newer aluminium wires and 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.{{citation needed|date=January 2017}}

For very high currents in electrical apparatus, and for high currents distributed through a building, bus bars can be used. (The term "bus" is a contraction of the Latin ''omnibus'' – meaning "for all".) Each live ("hot") conductor of such a system is a rigid piece of copper or aluminium, usually in flat bars (but sometimes as tubing or other shapes). Open bus bars are never used in publicly accessible areas, although they are used in manufacturing plants and power company switch yards to gain the benefit of air cooling. A variation is to use heavy cables, especially where it is desirable to transpose or "roll" phases.

* [http://www.nfpa.org/aboutthecodes/list_of_codes_and_standards.asp National Electrical Code] {{Webarchive|url=https://web.archive.org/web/20110728013724/http://www.nfpa.org/aboutthecodes/list_of_codes_and_standards.asp |date=28 July 2011 }} — Basis of most US electrical codes. Choose NFPA 70 (general purpose) or NFPA 70A (one and two family dwellings). Free registration required.