National Electrical Code (NEC)
The National Electrical Code (NEC), or NFPA 70, is a set of guidelines for the safe installation of electrical wiring and equipment in the United States that is regionally adoptable. Developed by the National Fire Protection Association, the NEC consists of twenty code-making panels and a technical correlating committee. The American National Standards Institute (ANSI) approves the NEC as an American national standard and is formally identified as ANSI/NFPA 70.
The NEC is updated and published every three years and was first published in 1897. Within a few years of publication, most states adopt the updated version of the NEC. Although it contains the term “national”, it is not a federal law and is typically adopted by states and municipalities in an effort to standardize their enforcement of safe electrical practices. Some sections are regularly omitted or modified by jurisdictions, and they may even add their own requirements based upon earlier versions of the NEC or other locally accepted practices.
Compose of four parts, the NEC includes an introduction, nine chapters, annexes A through J, and the index.
Introduction: gives all information that is general in nature including the purpose, scope, enforcement, and rules or information.
Chapters 1-4: definitions and rules for installations, circuits and circuit protection, methods and materials for wiring, and general-purpose equipment.
Chapters 5-7: deal with special occupancies, special equipment, and special conditions.
Chapter 8: specific to additional requirements for communications systems
Chapter 9: composed of tables regarding conductor, cable, and conduit properties.
Annexes A-J: relate to referenced standards, calculations, examples, additional tables for proper implementation of various code articles, and a model adoption ordinance
The introduction and first eight chapters of the NEC contain numbered articles, parts, sections (lists or tables), italicized sections, and informational notes and explanations that are not part of the rules. Articles are coded with numerals and letters, as ###.###(A)(#)(a).
Many NEC requirements refer to listed or labeled devices or appliances. These designations mean that the items have been designed, manufactured, tested or inspected, and marked in accordance with the requirements of the NEC. In order to be considered listed, devices must meet testing and other requirements set forth by a listing agency including Underwriters Laboratories (UL), SGS North America, Intertek, Canadian Standards Association (CSA), or FM Approvals (FM). Only a listed device can carry the listed brand or mark of the NEC. To be labeled as fit for a particular purpose, a device must be tested for that specific use by NEC, and then the appropriate label applied to the device.
Impact of the NEC
The National Electric Code affects nearly everyone involved with wire and cable. In particular, distributors, installers, OEM engineers, wire product engineers, and architects must incorporate NEC guidelines into their work.
Although NEC covers wire and cable installed in factories, office buildings, hotels, motels, apartment buildings, residences, and all cables that pass through any floor, wall, ceiling, or which travel in ducts, plenums, and other air-handling spaces, each individual municipality, city, county, or state can decide whether or not they wish to adopt the 1996 NEC as law.
Intended Uses of Appliance Wiring Materials (AWM)
In the past, AWM cable was incorrectly used to wire buildings—this was never its intended use. AWM cable is intended for internal wiring of factory-assembled, listed appliances such as computers, business machines, ranges, washers, dryers, radios, and televisions. In some cases, AWM cable may be used for external connection. In these situations, the user should be aware that AWM cable temperatures and voltage ratings may differ from NEC ratings.
|NEC Article - Type||Description||Plenum||Riser||Commercial||Residential|
|725 - CL2||Class 2 Cables||CL2P||CL2R||CL2||CL2X*|
|725 - CL3||Class 3 Cables||CL3P||CL3R||CL3||CL3X*|
|725 - PLTC||A stand-alone class. This is a power limited tray cable - a CL3-type cable that can be used outdoors. Is sunlight- and moisture-resistant and must pass the Vertical Tray flame test.||(none)||(none)||PLTC||(none)|
|760 - FPL||Power limited, fire protective, signaling circuit cable||FPLP||FPLR||FPL||(none)|
|770 - OFC||Fiber cable also containing metallic conductors||OFCP||OFCR||OFCG, OFC||(none)|
|770 - OFN||Fiber cable only containing optical fibers||OFNP||OFNR||OFNG, OFN||(none)|
|800 - CM||Communications||CMP||CMR||CMG, CM||CMX*|
|800 - MP||Multi-Purpose Cables||MPP||MPR||MPG, MP||(none)|
|820 - CATV||Community antenna television and radio distribution system||CATVP||CATVR||CATV||CATVX**|
|830 - BM||Network-powered broadband communications cable||BLP||BMR||BM||BLX|
|* Cable diameter must be less than 0.250"||** Cable diameter must be less than 0.375"|