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National Electrical Code Articles and Information

NEC Quiz: Article 330 Answers

by Mark Lamendola

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  1. It addresses Metal-Clad Cable Type MC. This type of cable is a factory assembly of insulated circuit conductors inside an armor of interlocking metal tape or inside a metal sheath (smooth or corrugated) [330.2]

  2. You can use Type MC cable in a dozen different defined general applications [330.10(A)]. One of those, wet locations, is permissible only if the particular Type MC being considered meets one of three conditions. Article 330 lists four specific uses for Type MC Cable [330.10(B)]: Cable tray, direct buried, service entrance cable, and outdoor aerial cable.

  3. You can't use it where it's subject to physical damage or where exposed to corrosive factors it's not designed to handle [330.12]. Regarding the physical damage, Type MC Cable, while inherently very strong, is not as strong as a solid conduit such as RMC or IMC. But it is lighter and usually easier to install and has other benefits that make it suitable for many applications in place of RMC or IMC. It fills a niche between these stiff-walled conduits and lighter duty flexible conduits.

  4. Before answering that question, it's worth noting that the support issue is moot if you damage the cable during installation by exceeding its bend radius [330.24]. Generally, you must support the cable every 6ft (or less) using approved support methods that don't damage the cable [330.30(A), (B), (C)]. But you don't have to support this cable if it's fished between access points in concealed spaces of finished structures, supporting is impractical, or it's running to a luminaire (or other equipment) and is less than 6ft from the last support [330.30(D)].

  5. You can use any terminations suitable for the conductors. You must use fittings listed and identified for use with Type MC Cable [330.40].



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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