Your questions answered: Critical power: Backup, standby and emergency power in mission critical facilities

When designing backup, standby and emergency power systems for mission critical facilities, there are several considerations beyond NFPA 70: National Electrical Code, NFPA 110: Standard for Emergency and Standby Power Systems and other building code requirements that must be addressed. Electrical engineers must understand the owner’s project requirements for the building’s power systems. Mission critical facilities can include data centers, hospitals, laboratories, semiconductor manufacturing, pharmaceutical and other facilities where interruption of power would have a severe impact on operations and business.

Questions left unanswered during the Feb. 8, 2022, webcast are answered here by Zachary Carter, PE, LEED AP BD+C, Senior Electrical Engineer, IMEG Corp., St. Louis.

Is there a scenario where a design could need to adhere to Article 517 and Article 708 of NFPA 70: National Electrical Code?

Yes, perhaps if there is a community-based hospital where there are dedicated critical operations areas (DCOA, referenced in Article 708) within a health care facility.

What is Type 10 in regards to NFPA 110: Standard for Emergency and Standby Power Systems?

Type refers to the maximum time permitted before restoration of power: 10 seconds of power restoration time would be a Type 10 system.

Health care facilities: Considerations of system designs. Courtesy: Consulting-Specifying Engineer

Could ventilation, particularly smoke removal, be considered as “emergency system”?

Yes, it could fall under Article 700 and 701. In these situations, it’s in the designer’s best interest to contact the authority having jurisdiction.

Are elevators supposed to be on Article 700 or Article 701 and how is this determined?

The use of the elevator will classify the type of power to be connected to it. Also, the jurisdictional requirements may stipulate. Refer to 202 NEC 620. Part X 620.91 Informational Note No. 2 for more information. NEC Article 700 Emergency Systems and NEC Article 701 Legally Required Standby Systems are clarified when they are to be used.

If a UL 924 inverter is used for NFPA 101: Life Safety Code loads and is rated 90 minutes then doesn’t it qualify as the emergency power source and then the genset is not?

If an inverter (UL 924) is used for the Article 700 loads required for a building and meets requirements of Article 700 and the building is completely backed up with generator power, then the remaining components of the electrical system would be considered Article 702 (optional standby). This assumes there are no Article 701 or 708 loads in the building.

Which is the better choice of transfer switches between closed and open transition?

This depends on what functionality the transfer switch serves. Many times, hospitals and data centers are good candidates for closed transition transfer switches. The local utility company should be contacted before specifying closed transition transfer switches.

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