National Electrical Code Articles and Information
National Electrical Code Top Ten Tips: Article 424 -- Fixed Electric
Space Heating Equipment
by Mark Lamendola
Based on the 2017 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 424 items we deem most important, based
on the pervasiveness of confusion and the potential costs of same.
- Even though you use heat intermittently, any fixed heater must
be considered a continuous load for purposes of branch
circuit sizing [424.2(B)].
- If there's not enough space to allow for combustible materials,
you can't install the heater [424.13].
- You must provide a disconnecting means within sight of the
- Thermostatic controllers can also serve as the disconnecting
means, provided they comply with 424.20.
- All switches and breakers used as a disconnecting means must be
of the indicating type [414.21].
- Don't assume overcurrent protection automatically meets code.
Carefully examine 424.22 for each installation.
- If you install space heating cables, note that the NEC devotes
Part V of Article 424 to this equipment.
- If you install duct heaters, note that the NEC devotes Part VI
of Article 424 to this equipment.
- If you install resistance-type boilers, note that the NEC
devotes Part VII of Article 424 to this equipment.
- If you install electrode-type boilers, note that the NEC devotes
Part VIII of Article 424 to this equipment.
How the NEC is arranged
- The first four Chapters of the NEC apply to all installations.
- Article 90 precedes Chapter One, and establishes the authority of the NEC.
- Article 80 follows the body of the NEC; it exists as Annex H. It provides the requirements for administration.
- Chapters 5, 6, and 7 are the "special" chapters, covering special: occupancies, equipment, and conditions (in that order).
- Chapter 8 provides the requirements for communications systems.
- Chapter 9 provides tables.
- The appendices provide mostly reference information.
- 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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