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National Electrical Code Articles and Information

NEC Quiz: Article 392 Answers

by Mark Lamendola

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  1. This wiring method is cable tray. Article 392 covers cable tray systems, including ladder, ventilated trough, ventilated channel, solid bottom, etc. [392.1]. A cable tray system is a unit or assembly of units (or sections) and associated fittings. Its defining characteristic is it forms a tray. This is distinct from a gutter (gutters are taller and more cube-shaped). You lay cable in a tray, while you (normally) pull it through a raceway.

  2. You can use it as a support system for nearly any type of wiring system (service, feeder, and branch conductors but also communication, signaling, and control circuits) [392.10]. See the limitations in 392.10, which is rather long for subsection 10 compared to other Chapter 3 articles. Also, see Table 392.10(A) for a list of wiring methods and their associated Articles.

  3. You can't use cable tray in hoistways or where subject to severe physical damage [392.12]. This latter restriction is oddly stated. The "where subject to damage" clause is ubiquitous in subsection 12 throughout Chapter 3. Why Article 392 qualifies it with "severe" is not something this author understands. From an engineering perspective, you want to install wiring methods in a way that protects them from damage whether severe or not.

  4. You must install it as a system [392.18], using only components that go with the system.
  5. You must use only components that go with it. Follow the manufacturer's installation instructions. Now, this quiz has a certain format to fit Chapter 3 Articles. This can be misleading in this particular instance since Article 392 goes well beyond the typical Chapter 3 Article in terms of requirements. Be sure to read the entire Article if you're working with cable tray. We certainly did not cover it in this short quiz.



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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