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National Electrical Code Articles and Information

NEC Quiz: Article 370 Answers

by Mark Lamendola

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  1. In the prelude to the questions, we gave away the fact this is cablebus. We even give away is its defining characteristics. But the NEC mentions more [370.1]. A key characteristic is cablebus is designed to carry fault current and to withstand the magnetic forces of such current. That's one reason cablebus is so popular for feeder applications.

  2. First of all, the type of circuit does not matter. You can use it for branch, feeder, or service [370.10]. You can also use it for any voltage or current for which its spaced conductors are rated and where installed only for exposed work. You can also use it for non-exposed work where permitted in 370.18. The last permitted condition listed in 370.10 actually belongs in 370.12; see our next answer for why.

  3. That appears to be a trick question, since there are only two prohibited uses listed in 370.12. But if you read 370.10, it says the cablebus can be used outdoors o rin corrosive, wet, or damp locations where identfied for the use. So if it's not identified for the use, you can't use it there. That's prohibited use number one. Another is that you can't use cablebus in hoistways. Nor can you use it in hazardous locations, unless it is specifically approved for the use (doesn't that remind you of the first prohibition we identified?).

  4. You have to use the blocks or other identified mounting means [370.30(B)] to support the conductors.

  5. You have to use approved fittings for these three conditions: Changes in direction of the run, dead ends, and terminations [370.42].

    This subsection also requires you to use approved fittings to provide additional protection where required. An example given is guards where subject to severe physical damage. This requirement, however, might not be satisfied just with fittings.

    Technically, this protection requirement does not even belong here. It's yet another of the many reiterations of the requirement in 300.4. The NEC is littered with this reiteration, making it seem as if protecting conductors, raceways, and cables from damage is a special case thing that nobody would otherwise think to do. Perhaps someday, the Code-Making Panels will clean up this mess by removing all of these special mentions that just waste space in an already large NEC and replace all of them with a single requirement stated in Article 110 where it belongs. The current text violates the organizational rules of the NEC and it simply isn't necessary to repeat the same thing over and over.



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.



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