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At first glance, the National Electrical Code (NEC) is an intimidating-looking book. Coming in at over seven hundred pages, it’s difficult to know where to begin. Thus, a basic overview of the layout and numbering of the NEC can be tremendously helpful in getting started.

To begin with, the NEC is divided as follows:

  • History – Gives a brief snippet about the current version of the NEC, followed by its origin and development.
  • Table of Contents – Lists each portion of the Code broken down by Chapter and Article.
  • List of Code Panels – Describes the contributors and representatives who oversaw each particular chapter.
  • Introduction (Article 90) – Explains the scope and use of the NEC.
  • Chapters 1-4 – Apply generally to all electrical installations.
    • Chapter 1: General (basic requirements applying to all equipment and installations)
    • Chapter 2: Wiring and Protection (types of circuits and methods of protection)
    • Chapter 3: Wiring Methods and Materials (types of equipment used to distribute electricity)
    • Chapter 4: Equipment for General Use (types of electrical devices commonly found in installations, i.e., lights, motors, and receptacles)
  • Chapters 5-7 – Supplement or modify Chapters 1-4.
    • Chapter 5: Special Occupancies (i.e. hazardous locations, places of public assembly, carnivals, etc.)
    • Chapter 6: Special Equipment (i.e. IT rooms, fire pumps, wind turbines, etc)
    • Chapter 7: Special Conditions (i.e. emergency power systems, low-voltage conditions, limited-energy conditions)
  • Chapter 8 – Not subject to Chapters 1-7 except when specifically mentioned.
    • Chapter 8: Communication Systems (information technology equipment, including television, radio, and telephone)
  • Chapter 9 – Applies where referenced.
    • Chapter 9: Tables (mandatory reference information as cited by other chapters)
  • Annexes – Information-only purposes (not a mandatory part of the code)

Each Chapter contains several Articles which are numbered based on the Chapter (i.e. “Article 100: Definitions” is found in Chapter 1, “Article 430: Motors, Motor Circuits, and Controllers” is found in Chapter 4, “Article 690: Solar Photovoltaic Systems” is found in Chapter 6, etc.). Finally, each Article contains several Sections, which are numbers in decimal format following the Article number (i.e. Article 250 contains several sections such as 250.10, 250.12, 250.20, etc).

Thus, Sections of the NEC are referenced as follows: (Chapter Number)(Article Number).Section. For example, Article 250: Grounding and Bonding is one of the most commonly referenced part of the NEC. So if you see a reference to “NEC 250.10” in a specification or other technical document, you immediately know it is located in Chapter 2 of the NEC, and it is in Article 250 (Grounding and Bonding). Section 10 of this Article happens to be entitled “Protection of Ground Clamps and Fittings.”

Knowledge of the NEC’s format is half the battle when it comes to quality electrical installations. The other half is implementation!