This article is about building wiring. Wiring is subject to safety standards for design and installation. Associated circuit protection, control and distribution devices within a building’s wiring system are subject to voltage, current and house wiring pdf download specification.
Wiring safety codes vary by locality, country or region. NZS 3000 standard, commonly known as the “wiring rules”, specifies requirements for the selection and installation of electrical equipment, and the design and testing of such installations. Hence national standards follow an identical system of sections and chapters. However, this standard is not written in such language that it can readily be adopted as a national wiring code. Neither is it designed for field use by electrical tradesmen and inspectors for testing compliance with national wiring standards.
By contrast, national codes, such as the NEC or CSA C22. 1, generally exemplify the common objectives of IEC 60364, but provide specific rules in a form that allows for guidance of those installing and inspecting electrical systems. DIN VDE 0100 is the German wiring regulations document harmonised with IEC 60364. 1881 to regulate installations of electric lighting.
States, counties or cities often include the NEC in their local building codes by reference along with local differences. The NEC is modified every three years. It is a consensus code considering suggestions from interested parties. The Canadian code reprints Chapter 13 of IEC 60364, but there are no numerical criteria listed in that chapter to assess the adequacy of any electrical installation.
Although the US and Canadian national standards deal with the same physical phenomena and broadly similar objectives, they differ occasionally in technical detail. US and Canadian standards are slowly converging toward each other, in a process known as harmonisation. The first edition was published in 1882. Many local rules and exceptions exist per country, state or region. Older installations vary in colour codes, and colours may fade with insulation exposure to heat, light and ageing.
The introduction of the NEC clearly states that it is not intended to be a design manual, and therefore, creating a color code for ungrounded or “hot” conductors falls outside the scope and purpose of the NEC. However, it is a common misconception that “hot” conductor color-coding is required by the Code. 480-volt systems use gray insulation, although this particular color code is not currently an explicit requirement of the NEC. In the UK, phases could be identified as being live by using coloured indicator lights: red, yellow and blue. The new cable colours of brown, black and grey do not lend themselves to coloured indicators.
For this reason, three-phase control panels will often use indicator lights of the old colours. Needed only if 120 V also is required. Cables may have an uninsulated PE which is sleeved with the appropriate identifying colours at both ends, especially in the UK. Australian and New Zealand wiring standards allow both Australian and European colour codes. However, TPS “Building Wire” to European colour codes is not generallay available in Australia and New Zealand. Care must be taken when determining the system used in any existing wiring. The protective earth conductor is now separately insulated throughout all cables.