The NEC, or National Electric Code, is the national safety standard for electrical design, inspection and installation in the United States. The code, also know as the NPFA 70, covers the installation of electrical equipment, conductors, raceways and installations using electrical wiring in commercial, residential and industrial areas.
The first version of the NEC was published in 1897, and the code is updated every three-year period. As of 2014, the latest applicable version of the NEC is the 2014 version. Adoption in individual states varies somewhat, but a majority of states complete transition from version to version within a two-year period.