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National Electrical Code Articles and Information

NEC Quiz: Article 353 Answers

by Mark Lamendola

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  1. In the prelude to the questions, we gave away the fact this is a nonmetallic conduit. What we didn't give away is the particular type. This is High Density Polyethylene Conduit (HDPE) [353.1, 353.2].

    Polyethylene is a type of plastic made from petroleum. It's inexpensive (if you discount the costs of the oil wars, environmental damage, etc.) and is widely used. It is also highly toxic, both in normal condition (you can smell its toxic fumes wafting off of products made from it) and egregiously so when burned. Try to avoid using it anywhere that humans are likely to spend much time.

  2. Article 353 lists six permitted uses [353.10]. Even though these are permitted, you should avoid using HDPE when another (nonplastic) type of material is suitable for the conditions and application.

  3. Article 353 lists five prohibited uses [353.12]. One of those is in hazardous locations; that's because plastic and static electricity tend to be ready playmates. Two of the other prohibited uses are for the protection of the conduit itself (where subject to temperatures above 122 DegrF and where exposed). But the other one, within a building, is a small consolation to the fact this highly toxic material is, well, highly toxic.

    On the Wireville site, Frank Bisbee has covered the fact that the European Union far more widely limits the use of highly toxic materials in electrical installations. And not just in conduit but also as an electrical conductor insulating material. The Europeans have really objected to the use of Teflon, another outrageously toxic material that you should avoid using unless you have absolutely no other choice. And it's likely you will always have another choice.

  4. Though Article 353 doesn't explicitly say so, you have to install HDPE as a complete system, using the appropriate listed hangers, clamps, fittings, and so forth. Pay close attention to the MDS and product labels. Article 353 does give explicit commentary regarding bend radii and number of bends [353.24].

  5. Use only bushings, couplings, connectors, brackets, etc., listed for use with HDPE (not stated in subsection 353.42 because there isn't one; see 353.28, 353.30, and 353.48.

    Really, you should not be installing this wiring method until you have had specific training in the installation methods and safety features. If you are the project engineer, factor that training into your budget so your project doesn't incur rework costs and health liability baggage.



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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