NFPA 70: National Electrical Code (NEC), 2017


NFPA 70-2017 - National Electrical Code NEC


Most standards are subject to periodic revision, having to undergo changes every certain number of years. For national codes, a strict revision process is unquestionably essential, since the changes adopted to retain the standards’ relevancy and reliability generally become part of the official practice used nationwide. For this reason, the National Electrical Code (NIC) is revised every three years, with the latest edition being released as NFPA 70-2017 - NFPA 70 National Electrical Code, 2017 edition.

NFPA 70-2017, like its predecessors, is the National Electrical Code (NEC) of the United States, striving for the ultimate goal of facilitating the safe installation of electrical wiring and equipment. The NEC is purposed with the practical safeguarding of persons and property from hazards arising from the installation of electrical components, and it is not intended as a design specification or an instruction manual on the practices that can coexist with those hazards. It should only be used by trained individuals.

The National Electrical Code covers the installation and removal of electrical conductors, equipment, and raceways, signaling and communications conductors, equipment, and raceways, and optical fiber cables and raceways for public and private premises, yards, lots, parking lots, carnivals, and industrial substations, installations of conductors and equipment that connect to the supply of electricity, and installations used by the electric utility.

Since the code covers practically all conceivable electrical installation processes, it is divided into several broad chapters, which are then broken down into articles composed of different smaller parts. The chapters of the document are the following:


  • Chapter 1 – General
  • Chapter 2 – Wiring and Production
  • Chapter 3 – Wiring Methods and Materials
  • Chapter 4 – Equipment for General Use
  • Chapter 5 – Special Occupancies
  • Chapter 6 – Special Equipment
  • Chapter 7 – Special Conditions
  • Chapter 8 – Communications Systems
  • Chapter 9 – Tables
  • Informative Annex A through Informative Annex J


Chapters 1 through 4 apply generally to all electrical installations, 5 through 7 are intended to supplement other chapters, 8 is subject to requirements of the earlier chapters where specifically referenced, the tables in Chapter 9 are to be used when needed, and the ten annexes are informatory only and should not be treated as mandatory for compliance.

As for the changes to NFPA 70-2017, they are abundant, since the document almost numbers 900 pages, and there is an alteration present on almost every single one of them. Whether large, such as a major addition of guidelines, or small, such the addition of a single word, every change made to NFPA 70-2017 from the 2014 version is shaded gray on the document.

An example of a minor change is the definition for cable routing assembly from the Article 100: Definitions section of Chapter 1, which appears as:


NFPA 70-2017 - National Electrical Code NEC1


Alternatively, a more substantial change to the NEC is the arc-flash hazard warning marking, for which the revision calls for additional information to be provided. It appears in NFPA 70-2017 as:


NFPA 70-2017 - National Electrical Code NEC
NFPA 70-2017 - National Electrical Code NEC2


As shown above, the 110.16 section contains a new subclause (B), which states that a permanent label should be applied to service equipment rated 1200 amps or more with the following information: nominal system voltage, available fault current at the service overcurrent protective devices, the clearing time of service overcurrent protective devices based on the available fault current at the service equipment, and the date the label was applied. All of this information should be easily obtainable at the time of installation.

Some adjustments made to NFPA 70-2017 are reflective of rising technologies, and they are necessary to keep the document current. For example, Article 690 of the code is devoted to solar photovoltaic (PV) systems, and the section is heavily encompassed by gray shading indicating additions and changes in content. For example, Part V for grounding and bonding appears as:


NFPA 70-2017 - National Electrical Code NEC3


All changes to the code can be found in the NFPA 70-2017 document.

NFPA 70-2017 - NFPA 70 National Electrical Code, 2017 edition is now available on the ANSI Webstore.


1. National Fire Protection Association (NFPA), NFPA 70-2017: NFPA 70 National Electrical Code, 2017 edition (Quincy: NFPA, 2016), 34.
2. National Fire Protection Association (NFPA), NFPA 70-2017: NFPA 70 National Electrical Code, 2017 edition (Quincy: NFPA, 2016), 45-6.
3. National Fire Protection Association (NFPA), NFPA 70-2017: NFPA 70 National Electrical Code, 2017 edition (Quincy: NFPA, 2016), 566.
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