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National Electrical Code Top Ten Tips: Article 400 -- Flexible Cords and Cables

Based on the 2023 NEC

by Mark Lamendola

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 400 items we deem most important, based on the pervasiveness of confusion and the potential costs of same.

  1. Donít dismiss flexible cords and fixture wires as not deserving your attention. There's a reason why the NEC covers them in two separate articles. Flexible cord requirements are in Article 400 and fixture wire requirements are in Article 402.
  2. The NEC does not consider flexible cords to be "a wiring method." That is why they are in Chapter 4 instead of Chapter 3. See the Table of Contents for Chapter 3 and you get an overview of the wiring methods acceptable to this Code. This has implications, such as the fact you don't affix flexible cords and fixture wires to building members.

  3. Article 400 applies to the cords and cables in Table 400.4, but it does not apply to the cables in Chapter 3 (e.g., NM, AC, or MC cable). That's because the Chapter 3 cables are wiring methods and the Article 400 cables are not.

  4. You must use the right cord (and fittings) for the application. This means you don't use a dry-rated cord in a wet location. The jacket material meets certain insulation properties and other characteristics only in the environment for which it is designed and approved.

  5. Table 400.4 is the heart of Article 400. Notice, this is much more than "a list of extension cords." Look over the entries in this table, and you will see its importance immediately.

  6. Chapter 3 deals heavily with ampacities for permanently installed wiring. Article 400 provides ampacities for flexible cords in  Tables 400.5(A)(1) and 400.5(A)(2). Don't forget to apply the adjustment factors from Table 400.5(A)(3), if applicable.

  7. The requirements for protecting cords not smaller than 18AWG from overcurrent are in 240.5.

  8. Look in [400.10], and youíll see 11 permitted uses for flexible cords. Rather than try to memorize this list, take a few minutes to go through it and examine the logic behind the uses. A key factor is the need for movement at the device.

    Note that this reference used to be 400.07 (until the 2020 revision), but there has been a concerted effort to standardize the layout of the Articles. Thus, you should see "Uses Permitted" under Subsection 10 in any NEC article that lists them. There may be some odd ones that have not yet been updated, thus "should" instead of "will" in the preceding sentence.
  9. Look in [400.12], and youíll see 7 uses not permitted for flexible cords. This is up from 6 in the 2017 revision (the change was made with the 2020 revision). Again, apply the logic. Do not try to use flexible cords in place of Chapter 3 wiring methods.

    Note that in earlier revisions, this reference wase 400.08, but there has been a concerted effort to standardize the layout of the Articles. Thus, you should see "Uses Not Permitted" under Subsection 12 in any NEC article that lists them. There may be some odd ones that have not yet been updated, thus "should" instead of "will" in the preceding sentence.

  10. Provide adequate protection for flexible cords when running them through holes in covers, boxes, etc. [400.17]. Bushings, grommets, and fittings are all possible solutions, but make sure you use the solution that is appropriate for that specific application. A grommet might be fine in one case, and inadequate in another.


Don't take your electrical exam twice

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.

Try your NEC moxy:

  • Do you know the difference between bonding and grounding? Hint: Look in the NEC, Article 100.
  • Does the NEC refer to grounding incorrectly in any of its articles? Yes! So be careful to apply the Article 100 definitions. Don't ground where you should bond.
  • When doing motor load calculations, which Article covers hermetic motors? Answer: While Article 440 covers the application of hermetic motors, it does so only by amending Article 430 because hermetic motors are a special case of motors. For motor load calculations, refer to Article 430.
  • Does the NEC provide a voltage drop requirement? Yes! It does so in a special case, which is Article 648 Sensitive Electronic Equipment. But for general applications, it does not provide a requirement; it merely provides a recommendation in a couple of FPNs.
  • Take our Code Quizzes.

Remember other applicable codes, rules, standards, and references:

  • OSHA's electrical worker safety rules.
  • IEEE standards.
  • NETA standards.
  • NFPA standards.
  • International Codes (if applicable to the installation).
  • State Codes (if the state has them).
  • Local ordinances and permit requirements.
  • Local fire codes.
  • Manufacturer requirements or guidelines.
  • Customer security requirements.
  • Industry standards.
  • Your company's own internal standards, practices, and procedures.
  • Engineering drawing notes.