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National Electrical Code Top Ten Tips: Article 408, Switchboards and Panelboards

Please note, we do quote from copyrighted material. While the NFPA does allow such quotes, it does so only for the purposes of education regarding the National Electrical Code. This article is not a substitute for the NEC.

These are the 10 NEC Article 408 items we deem most important, based on the pervasiveness of confusion and the potential costs of same.

  1. Respect the "modular integrity" philosophy of switchboard and panelboard installation. Don’t use any vertical section as a wireway between other vertical sections [408.3]. Keep all wiring in its own section, and don't mix wiring between sections.
  2. Bond all sections together, using a bonding jumper sized per Table 250.122 or Table 250.66 [408.3].
  3. You must arrange the phases in a particular order. That order is A, B, C--from front to back and from top to bottom (or left to right), when viewing the cabinet from the front [408.3].
  4. On Delta systems, you must designate the phase with the highest voltage to ground as the B phase [408.3].
  5. Fill out the circuit directory, and do so legibly with sufficient detail [408.4].
  6. Close any unused openings [408.7].
  7. If locating in wet locations or near combustible materials, follow the rules in 408.16 and 408.17.
  8. Classify your panelboard as either a power panelboard or a lighting panelboard (per 408.30), and then follow the appropriate instructions in Article 408, Part II.
  9. Provide protection on the supply side to each lighting and appliance panelboard. You can use one or two overcurrent protection devices, but not more [408.36].
  10. Observe the minimum spacing requirements provided in Table 408.56.

 

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How the NEC is arranged

  1. The first four Chapters of the NEC apply to all installations.
  2. Article 90 precedes Chapter One, and establishes the authority of the NEC.
  3. Article 80 follows the body of the NEC; it exists as Annex H. It provides the requirements for administration.
  4. Chapters 5, 6, and 7 are the "special" chapters, covering special: occupancies, equipment, and conditions (in that order).
  5. Chapter 8 provides the requirements for communications systems.
  6. Chapter 9 provides tables.
  7. The appendices provide mostly reference information.
  8. Appendix D contains examples that every NEC user should study.

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