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National Electrical Code Articles and Information

NEC Quiz: Article 334 Answers

by Mark Lamendola

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  1. It addresses cables that have a sheath made of something other than metal. Thus, "Nonmetallic-sheathed cable" or Types NM, NMC, and NMS. The C stands for "corrosion-resistant" and the S stands for "Signal."

  2. You can use all three types of cable in five different defined applications [334.10(10-(5)]. Additionally, you can use:
    Type NM cable in two different defined applications [334.10(A)].
    Type NMC cable in three different defined applications [334.10(B)].
    Type NMS cable in two different defined applications [334.10(C)].

  3. You can't use it any of these in any of the ten applications listed in 334.12(A). Those are any structure not specifically permitted, exposed in dropped or suspended ceilings (except residential), as service entrance cable, in classified garages having hazardous locations defined in 511.3, and six other applications listed in that subsection.

    Additionally, you can't use Types NMC or NMS in any of the four conditions identified in 334.12(B).

  4. Generally, you must support the cable every 6ft (or less) using staples, straps, hangers, or similar fittings [334.30(A)]. But you don't have to support this cable if it's fished between access points in concealed spaces of finished structures, or supporting is impractical [334.30(B)].

  5. You can use any terminations suitable for the conductors. The NEC says almost nothing on this aspect of installation. But it very clearly says you can use only one conductor per screw terminal [334.40(B)].



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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