National Electrical Code Articles and Information
National Electrical Code Top Ten Tips: Article 409 -- Industrial Control Panels
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 409 items we deem most important, based
on the pervasiveness of confusion and the potential costs of same.
- Any control panel operating at 1000V or less must comply with Article 409 [409.1].
- An industrial control panel can have control circuits, power circuits,
- Quite a few other Articles apply to these panels, in addition to the
specific requirements of Article 409. See Table 409.3.
- Base the ampacity of the supply conductor on the sum of three items [409.20]:
A. 125% of the full-load current rating of all resistance heating loads
B. 125% of the full-load current rating of the highest rated motor.
C. Sum of the full-load current rating of all the other motors (and
apparatus) that may be operating at the same time.
- Provide overcurrent protection per Article 240, Parts I, II, and
- You can put overcurrent protection ahead of the panel or inside it [409.21(B)].
- You do not ground an industrial control panel. You bond it
- Don't use industrial control panels as junction boxes or as any kind of
feed-through system. Circuits that are not part of the panel must be routed
around it, not through it.
- Wire bending and spacing requirements do exist. Those nice 90 degree
bends for 5V systems do not belong inside a typical industrial control
panel. And if wiring is voluminous, simply dumping it in a gutter or routing
it inside plastic wrap isn't the solution. See 409.104 for requirements.
- Spacing requirements are critical. See Table 430.97(D) [409.106].
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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