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National Electrical Code Articles and Information

NEC Quiz: Article 320 Answers

by Mark Lamendola

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  1. Armored Cable (Type AC).

  2. There are five: for feeders and branch circuits in concealed or exposed installations, in cable trays, in dry locations, embedded in plaster or brick or other masonry but not in wet or damp locations, in the air voids of masonry where dry [320.10].

  3. There are five: where subject to physical damage, in damp or wet locations, in voids subject to moisture, where exposed to corrosive conditions, embedded in plaster or brick or other masonry if in wet or damp locations [320.12].

  4. It can't be less than five times the diameter of the cable [320.24]. However, this doesn't mean the "final" bending radius. It means that you do not exceed this at any time during the installation process. Once this radius is exceeded, the AC Cable is irreparably damaged.

  5. Support is a huge issue. Support requirements are not reduced by dint of using Type AC Cable. Subsection 320.30, which provides the support requirements for Type AC Cable, is the largest subsection in Article 320. Type AC cable isn't indestructible. It may help to think of is as a flexible version of wire that's been run in EMT or rigid. The walls of the raceway (the metal jacket is really an integrated raceway, making the wire and jacket a wiring system) are thinner, in this case. So the need for support and damage protection are, if anything, greater than for tubing or conduit.



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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