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National Electrical Code Articles and Information

NEC Quiz: Article 366 Answers

by Mark Lamendola

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  1. In the prelude to the questions, we gave away the fact this is a gutter. But of course the name of Article 366 gives that away also. What we didn't give away is its defining characteristics (though we did mention some of them). An auxiliary gutter can be metallic or nonmetallic [366.2]. If the latter, it's flame-retardant. Either way, it's an enclosure with hinged or removable covers. It's designed such that you lay or set (as opposed to pull, as you would with conduit or tubing) the conductors in place (after the complete system is installed) and then close the covers.

  2. Unlike the conduit and tubing Articles, Article 366 doesn't present a list of permitted uses. Instead, it provides the requirements for using metallic ones indoors and outdoors, then does the same thing for nonmetallic ones [366.10]. Basically, you have to use gutters that are listed for the application.

  3. Article 366 does list two prohibited uses [366.12]. You can't enclose switches, overcurrent devices, appliances, or similar equipment [366.12(1)]. Nor can you extend more than 30 ft beyond the equipment it supplements [366.12(2)]. There is an exception to that distance limit, and it applies to elevators.

  4. Oddly enough, the NEC does not explicity say what type of hardware you can use. But since these gutters are sold and assembled as systems, common sense tells us that you use hardware that's consistent with what comes in the gutter kit and/or that is appropriate for it. It does say that you must secure each metallic gutter for its entire length at intervals of no less than 5 ft [366.30(A)]. It also provides a more stringent support requirement for nonmetallic gutters [366.30(B)].

  5. Joints between some lengths of gutter might need to be replaced with expansion fittings. In fact, you must install expansion fittings where temperature changes might cause a change in gutter length of more than 6 mm (quarter inch) [366.44].



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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