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National Electrical Code Top Ten Tips: Article 426 -- De-icing and Snow-melting equipment

by Mark Lamendola

Based on the 2011 NEC

Please note, we do quote from copyrighted material. While the NFPA does allow such quotes, it does so only for the purposes of education regarding the National Electrical Code. This article is not a substitute for the NEC.

These are the 10 NEC Article 426 items we deem most important, based on the pervasiveness of confusion and the potential costs of same.

  1. It doesn't matter if these systems are embedded or exposed. If it's an electrically energized heating system used for melting snow or ice, it must comply with Article 426.
     
  2. Article 426 recognizes three kinds of heating systems: Impedance, resistance, and skin-effect.
     
  3. If you use any cord-and-plug equipment, it must also comply with Article 422.
     
  4. Don't apply load diversity or similar factors to equipment covered by Article 426. You must consider all such equipment to be a continuous load.
     
  5. Keep protection as a foremost thought. Protect the equipment from damage, and protect people from thermal burns and electric shock by using the proper installation techniques.
     
  6. General requirements are in Part I.
     
  7. General installation requirements are in Part II.
     
  8. You'll find the specific requirements for Resistance, Impedance, and Skin-effect type elements in Parts III, IV, and V, respectively. While these have similarities, don't apply the wrong Part to the system in question.
     
  9. Part VI, titled, "Control and Protection," is chiefly concerned with the disconnecting means.
     
  10. Ensure your controllers conform to 426.51 and your provide overcurrent protection in conformance with 426.52.

 

 

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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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