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National Electrical Code Articles and Information

Based on the 2014 NEC

by Mark Lamendola

National Electrical Code Tips: Article 692 -- Fuel Cell Systems

Fuel cells rated for commercial and industrial use typically are purchased as engineered systems, skids, or units. But there's also typically quite a bit of design involved at the site. Not so much in accommodating the fuel cells (e.g., transfer switches and switchgear) but in figuring out the overall power strategy for the site.

A great example of this is the First National Bank of Omaha's facility that uses fuel cells as its primary power source and more fuel cells as its secondary source. This particular example has been a frequently cited case study for groups such as the 7x24 Exchange.

This is true in no small part because fuel cells are so initially expensive relative to other types of power sources plus have ongoing costs for maintenance and cell change. If you're going to add one, you need to make it worthwhile in terms of cash flow (unless the financials are not determining factors).

Typically, the NEC requirements are not limiting factors in the design and installation of a fuel cell system, because the typical owner commissions the project to increase uptime and reliability. This means the typical owner is asking, "What are the potential problems and how can I avoid them" rather than looking at the NEC and asking, "What can I get by with."

Still, not all owners are typical and the NEC would be remiss if it didn't provide some minimum requirements for these systems. Let's address some highlights of those.



  1. As with any non-utility power source, fuel cells must be listed on a plaque or directory (along with all other power sources) at each service equipment location [692.4(B)].
     
  2. Exactly who is going to install the fuel cell system? The NEC says only a qualified person can do this [692.4(C) but instead of specifying what that means it refers you to the general definition in Article 100. If you read that definition, you see several key concepts such as necessary skills and safety training to work on the equipment. Note that this doesn't mean you hire an installer with previous experience (experience doesn't mean you've had the required training or have the knowledge; lots of people "wing it" and then claim they have experience). Read this carefully, then think through the specifics. Whether you are the installer or are hiring one, consult with manufacturers to get their view on what's necessary.
     
  3. If it's a stand-alone system, that doesn't make it something isolated where the NEC doesn't apply. Whether the NEC applies or not is irrelevant to whether or not you have a utility connection. Regardless of the power source, the premises wiring must meet Code and that rule applies to premises supplied by fuel cells too [692.9].
     
  4. Normally, you size your service conductors based on your calculated load. But with a fuel cell system, their counterparts (conductors between the fuel cell system output and the building disconnect) must be sized based on the output rating of the fuel cells [692.10(B)]
     
  5. You must provide a disconnect that can disconnect all current-carrying conductors of a fuel cell system from all other conductors in a structure [692.13]. That is, you must be able to isolate the fuel cell from the structure, electrically. Among the reasons for doing this so that fire personnel can de-energize before entering the structure.
     
  6. You can use any Chapter 3 wiring method. Also, you can use any wiring method that is intended and designed for use with fuel cell systems (this applies to fittings also) [692.31].
     
  7. The grounding requirements depend upon whether the system is AC (apply 250.20, 250.30), DC (apply 250.160), or both (apply 250.66 for the AC and 250.166 for the DC) [692.41].
     
  8. You must install a separate equipment "grounding" (bonding) conductor [692.44] and it must be sized per 250.122 [692.45].
     
  9. You must provide signs and markings for the fuel cell power sources [692.53], manual fuel shut-off valve [692.54], and (if present) stored energy system (e.g., batteries) [692.55].
     
  10. If the system is interactive (e.g., premises wiring also connect with the utility), you must follow the requirements laid out in Part VII. These include using a transfer switch, using only fuel cell systems identified and marked for interactive use, and following some requirements specified in Article 705.

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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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