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"

C(UL) Certifications

UL/NEC-Approved cables may also be C(UL)/CEC-Approved as communications cables meeting the requirements of the Bi-National Standard CSA C22.2 No. 214/ UL 444 and Section 60 of the Canadian Electrical Code, Part I (CEC). The C(UL) cable designation (and its meaning) would be one of the following:

  1. CMP — Cable meeting CSA FT6 or UL 910
  2. CMR — Cable meeting UL 1666
  3. CMG — Cable meeting CSA FT4
  4. CM — Cable meeting UL 1581, Sec. 1160 (Vertical-Tray)
  5. CMX — meeting UL 1581, Sec. 1080 (VW-1)
  6. CMH — Cable meeting CSA FT1

The CSA flame tests are defined in CSA 22.2 No. 0.3 as follows:

FT1 Vertical Flame Test -- per C.S.A. 22.2 No. 0.3-92 Para 4.11.1

A finished cable shall not propagate a flame or continue to burn for more than one (1) minute after five (5) fifteen (15) second applications of the test flame. There are an interval of fifteen (15) seconds between flame applications. The flame test shall be performed in accordance with Para 4.11.1 of Canadian Standards Association (CSA) Standard C22.2 No. 0.3. In addition, if more than 25% of the indicator flag is burned, the test cable fails.

FT4 Vertical Flame Test -- Cables in cable trays per C.S.A. C22.2 No. 0.3-92 Para 4.11.1

The FT4 Vertical Flame Test — Cables in Cable Trays is similar to the UL-1581 Vertical Tray Flame Test, but is more severe. The FT4 test has its burner mounted at 20° from the horizontal with the burner ports facing up. The UL-1581 Vertical Tray has its burner at 0° from the horizontal. The FT4 samples must be larger than 13mm (.512″) in diameter.

If not, then the cable samples are grouped in units of at least three (3) to obtain a grouped overall diameter of 13mm. The UL-1581 Vertical Tray does not distinguish on cable size. The FT4 has a maximum char height of 1.5 m (59″) measured from the lower edge of the burner face. The UL-1581 has a flame height allowable up to approximately 78″ measured from the burner.

FT6 Horizontal Flame and Smoke Test -- per C.S.A. 22.2 No. 0.3-92 Appendix B

Products passing the FT6 Horizontal Flame and Smoke Test are designated FT6 in the column where the trade number appears. This test is for cables that must pass a Horizontal Flame and Smoke Test in accordance with ANSI/NFPA Standard 262-1985 (UL-910). The maximum flame spread shall be 1.50 meters (4.92 ft.). The smoke density shall be 0.5 at peak optical density and 0.15 at maximum average optical density.

NEC Cable Substitution

Types: BMR, BM, BLP, BLX
Network - Powered Broadband Communications Cable
Community Antenna Television and Radio Distribution Cables
Types: CL3P, CL3R, CL3, CL3X, CL2P, CL2R, CL2, CL2X
Class 2 and Class 3 Remote-Control, Signaling and Power Limited Cables
Communication Cables
Power Limited Fire Alarm Cables
Conductive Optical Fiber Cables
Nonconductive Optical Fiber Cables
Types: PLTC
Power Limited Tray Cables