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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.