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National Electrical Code Articles and Information

NEC Quiz: Article 424, Part 9 Answers

by Mark Lamendola

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  1. It applies to what the title says [424.90], but if you don't know what a radiant heating panel is that doesn't help much. And the definitions provided in 424.91 are vague. So let's explain that. The heater is radiant (heats by emitting heat energy from an element to warm people and objects), as opposed to convection heat (heats the air). And it's a panel, as opposed to being a floor system. It could be a wall panel or a ceiling panel, for example. And it's ready for connection to a branch circuit [424.91].

  2. This is not a Code question, but understanding this can help with the installation. These kinds of heaters are typically used to supplement other forms of heat. For example, a house may be heated by a central air system but the master bathroom might have a wall panel heater. Note also that each unit must be identified as suitable for the installation [424.92(B)].

  3. They must be at least two inches away [424.93(A)(3)].

  4. Yes, but only if you follow the requirements of 424.98. For example, you can't install them across expansion joints unless you make provision for expansions and contractions [424.98(B)].
  5. It must have GFCI protection 424.99(B)(5). This "could" be acheived with a GFCI receptacle ahead of that portion of the circuit supplying the heater(s). But this is a poor design for multiple reasons. A better way to do it is to use a GFCI breaker for that circuit. Though not NEC-required, using a combo AFCI/GFCI breaker would be the best way to go. This way, you protect individuals from electric shock and also protect the circuit from arc fault.



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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