National Electrical Code ExplanationsBased on the 2014 NEC
National Electrical Code Tips: Article 750, Energy Management Systems
At about 1.5 pages long, this is one of the shortest NEC Articles. It's also new with the 2014 NEC (as is the even shorter Article 728, which precedes it in Code order).
- Typically, a Code Article will expound on the installation requirements for whatever it covers. For example, Article 430 really goes into depth about motors. This Article does not go into depth about energy management systems. It merely provides a few restrictions on their installation and application.
- The expectation is that you, as the designer or installer, are a qualified person using the relevant industry standards. Other codes may provide more restrictions or prescriptions than Article 750 [Informational Note, 750.1]. That is, Article 750 doesn't replace other codes or standards. It simply adds the voice of the NEC to them.
- The systems covered by this Article are those that monitor/and or control loads or power sources [750.2].
- Both "control" and "monitor" are specifically defined in this Article. What's key in both definitions is the involvement of electric power.
- An energy management system cannot override any control necesssary to ensrue the continuity of alternate power sources for fire pumps, health care facilities, emergency systems, legally required systems, or critical operations power systems [750.20].
- The system can monitor the loads just described [750.30], and it can control these to a limited extent [750.30(A)].
- The system cannot disconnect the power to elevators (or escalators, moving walks, or stairway lift chairs), positive mechanical ventilation for hazardous locations, ventilation used to exhaust hazardous gas or reclassify an area, emergency lighting, or essential systems in health care facilities [750.30(B)].
- Be careful in how the energy management system adds loads. It isn't permitted to overload a branch circuit, feeder, or service [750.20(C)]. This could happen in any number of ways. Also, don't make the mistake of adding too many loads to these circuits and then relying on the energy management system to keep things sorted out. Do the sorting out in your design. Use the energy management system to reduce total energy consumption, not to add phantom capacity to branch circuits, feeders, and services.
- Protect those first responders. On the enclosure of the controller, disconnect, or branch-circuit OCPD, post a directory showing which devices and circuits the system controls [750.50].
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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