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The National Electrical Code (NEC), or NFPA 70, is a regionally adoptable standard for the safe installation of electrical wiring and equipment in the United States. It is part of the National Fire Code series published by the National Fire Protection Association (NFPA), a private trade association . [ 1 ]
An electrical code is a term for a set of regulations for the design and installation of electrical wiring in a building. The intention of such regulations is to provide standards to ensure electrical wiring systems are safe for people and property, protecting them from electrical shock and fire hazards. They are usually based on a model code ...
BS 7671 only covers electrical systems with the following characteristics [5]: having a nominal voltage up to but not exceeding 1000V AC or 1500V DC for AC having a supply frequency of 50 , 60 or 400Hz , though the use of other frequencies for special purposes is not excluded.
A set of wiring diagrams may be required by the electrical inspection authority to approve connection of the residence to the public electrical supply system. Wiring diagrams will also include panel schedules for circuit breaker panelboards, and riser diagrams for special services such as fire alarm or closed-circuit television or other special ...
The most common three-phase system will have three hot legs, 208 V to each other and 120 V each to the neutral. An older, but still widely used, high-leg delta system uses three phases with 240 volts phase-to-phase for motor loads, and 120 volts for lighting loads by use of a center-tapped transformer; two of the phases are 120 volts to neutral ...
Homes typically have several kinds of home wiring, including electrical wiring for lighting and power distribution, permanently installed and portable appliances, telephone systems, heating or ventilation system control, and increasingly for home theatre and computer networks.
While the various OSHA, ASTM, IEEE and NEC standard provide guidelines for performance, NFPA 70E addresses practices and is widely considered as the de facto standard for Electrical Safety in the Workplace. Practices include: Staging a "safe work zone" with boundaries, barricades, signs and attendants.
The NEC Zone system was created to harmonize with IEC classification system, and therefore reduce the complexity of management. Canada has a similar system with CSA Group standard C22.1, the Canadian Electrical Code, which defines area classification and installation principles. Two possible classifications are described, in Section 18 (Zones ...