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National Electrical Code Articles and Information

Based on the 2020 NEC

by Mark Lamendola

National Electrical Code Top Ten Tips: Article 552 -- Park Trailers

  1. Article 552 covers the electrical equipment and conductors (for park trailers) not already covered by Article 550 or 551 [550.1]

  2. A park trailer is not a permanent dwelling, nor is it intended for commercial use. It is intended for seasonal use [552.4].
  3. Splices must be made in a particular way; one aspect is they must be mechanically and electrically secure (as is not the case when soldering together two wires that are not first mechanically joined) [552.10(C)(2)].
  4. You must separate the power wiring from all other wiring [552.10(C)(3)].
  5. For low voltage overcurrent protection, rate your overcurrent devices per Table552.10(E)(1)].
  6. Locate the overcurrent protection devices in an accessible location within 18 inches of where the trailer power supply connects to its circuits [552.10(E)(4)].
  7. If you use a voltage converter to supply 120V, the wiring of the unit must comply with the requirements of Parts I and IV of Article 552 [552.20(B)].
  8. The rule above also applies if you connect to a nominal 120V/240V source, but in addition it must comply with Parts III and V of Article 552 [552.40].
  9. The distribution panelboard must have an equipment grounding (bonding) terminal [552.45(A)].
  10. The requirements for branch circuit determination are detailed, and should be reviewed prior to final approval of any wiring design. You'll find those in 552.46.

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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