National Electrical Code
It is typically adopted by states and municipalities in an effort to standardize their enforcement of safe electrical practices.
[2] In some cases, the NEC is amended, altered and may even be rejected in lieu of regional regulations as voted on by local governing bodies.
As with any "uniform" code, jurisdictions may regularly omit or modify some sections, or add their own requirements (sometimes based upon earlier versions of the NEC, or locally accepted practices).
[5] In the United States, anyone, including the city issuing building permits, may face a civil liability lawsuit for negligently creating a situation that results in loss of life or property.
That creates a system whereby a city can best avoid lawsuits by adopting a single standard set of building code laws.
[7] The NEC also contains information about the official definition of HAZLOC and the related standards given by the Occupational Safety and Health Administration and dealing with hazardous locations such as explosive atmospheres.
Once the coding model has been accepted as law, it loses copyright protection and may be freely obtained at no cost.
For example, 805.133(A)(1)(a)(1), would be read as "article 805, section 133, item (A) Separation from Other Conductors, specific (1) In Raceways, cable Trays, Boxes,... inclusion (a) Other Circuits, precise inclusion (1) Class 2 and Class 3...." and would be found in Chapter 8, Part IV Installation Methods Within Buildings.
These are examples of "national recognized testing laboratories" (NRTL) approved by the U.S. Department of Labor's Occupational Safety and Health Administration (OSHA) under the requirements of 29 CFR 1910.7.
Because of the reputation of these listing agencies, the "authority having jurisdiction" ( or "AHJ" – as they are commonly known) usually will quickly accept any device, appliance, or piece of equipment having such a label, provided that an end user or installer uses the product in accordance with manufacturer's instructions and the limitations of the listing standard.
However, an AHJ, under the National Electrical Code provisions, has the authority to deny approval for even listed and labeled products.
Likewise, an AHJ may make a written approval of an installation or product that does not meet either NEC or listing requirements, although this is normally done only after an appropriate review of the specific conditions of a particular case or location.
Today, a new aluminum wire (AA-8000) has been approved for branch circuits that does not cause corrosion where it contacts copper, but it is not readily available and is not manufactured below size #8 AWG.
A ground fault circuit interrupter (GFCI) is required for all receptacles in wet locations defined in the Code.
The NEC also has rules about how many circuits and receptacles should be placed in a given residential dwelling, and how far apart they can be in a given type of room, based upon the typical cord length of small appliances.
The 1999 Code required that new 120/240 volt receptacles, such as those for electric ranges and dryers, be grounded also, which necessitates a fourth slot in their faces.
Additional protection such as NM cable inside raceway is needed if the installation method is subjected to physical damage as determined by the authority having jurisdiction.
Derating is necessary because multiple conductors carrying full-load power generate heat that may exceed the normal insulation temperature rating.
This gives them a greater heat dissipation rating than standard three-wire NM-2 cable, which includes two tightly bundled load and return wires.
In 2016, the group PUBLIC.RESOURCE.ORG, INC published copies of the code online free of cost, arguing that as a standard adopted as law, it should be publicly available.
The case challenges the nature of funding sources for development of the standards, which are often adopted as law, but created without taxpayer dollars.
