Kuegler Associates: Consulting Engineers - Designed Right = Built Right

For those who might not be familiar with it, or just need a quick refresher, NFPA 110 is the standard established by the National Fire Protection Association to cover performance requirements for emergency and standby power systems generators providing an alternate source of electrical power in buildings and facilities in the event that the normal electrical power source or electric utility fails. While this is certainly important for just about any retail, commercial, industrial, or governmental building, it is especially important for mission-critical facilities that can have an impact of public health, safety, and welfare. In this post, we’re going to look at the major issues that may be involved when it comes to complying with NFPA 110 in mission-critical facilities.

Safety, maintainability, code compliance, and even economics all play crucial roles in determining the topology of a backup system for a facility such as a hospital, emergency management center, water & sewer utilities or a datacenter. In large facilities where an electrical failure can result in significant economic loss, facilities owners will typically employ a backup power system that they can ideally use to support their emergency, legally-required standby loads and owner optional standby.  In this case, the design engineer must take into account the effects of combining emergency, legally-required, and optional standby systems  to meet the requirements of NFPA 110-2013: Standard for Emergency and Standby Power Systems and NFPA 70-2014: National Electrical Code (NEC). The engineer also needs to consider code compliance while keeping maintainability and economics in mind. Engineers may also have to balance onsite solar and their effects and control.

Some of the challenges design engineers can face with NFP-110 compliance include:

Properly defining system levels It’s important to carefully evaluate the loads being served and coordinate with the authority having jurisdiction (AHJ). According to Annex A.4.4.1, “Level 1 systems are intended to automatically supply illumination or power, or both, to critical areas and equipment … Essential electrical systems can provide power for the following essential functions: life safety illumination, fire detection and alarm systems, elevators, fire pumps, public safety communications systems, industrial processes where current interruption would produce serious life safety or health hazards, and essential ventilating and smoke removal systems.” This has been interpreted by some jurisdictions as meaning that any electrical system that includes these types of loads is a Level 1 system.

Fuel storage requirements According to Annex A.4.2, 96 hours of fuel may be required in certain seismic zones. In summary, “Where the seismic design category is C, D, E, or F, as determined in accordance with ASCE/SEI 7: Minimum Design Loads for Buildings and Other Structures, the EPS supplying a Level 1 EPSS should be capable of a minimum 96 hr of operation without refueling if it is determined that EPS operation is necessary for this period.” This is a change from the 2010 standard where the 96-hr fuel requirement was called out explicitly in the body of NFPA 110. Again, this can be open to interpretation – some jurisdictions consider this a requirement to provide 96 hours of fuel whenever a Level 1 system is in a high seismic zone.

Accommodating small code-required loads Certain mission-critical facilities such as data centers actually have relatively small code-required loads even though a power failure can result in millions of dollars in losses. That’s why some facilities owners prefer electrical distribution systems that are just as robust, and in some cases more robust, as those needed for Level 1 EPSS life safety loads. “Mission critical” and “loss” can have different meanings for different people.

“Emergency” is also a misused term. Per the National Electric Code NFPA70, emergency is usually only the “emergency lighting” or as some codes refer to as “life safety illumination”. All other loads are then “legally required standby”, as required by some other code, and by definition all the rest are “optional standby” systems. Each of these definitions requires a different level of wiring method, which affects the installation.