NFPA codes + standards and emergency power supply systems
NFPA Journal®, January/February 2013
Occupancy type plays a major role in determining the size and complexity of emergency power systems. For example, a hospital and office building with similar square footage will have significant differences in the code-required features of their respective emergency systems.
However, there is one common feature to an emergency power system of any size or type of occupancy: a standby power source, or emergency power supply system (EPSS), that automatically provides power to the necessary electrical equipment in the event that the normal source (typically an electric utility) is interrupted. As we have once again learned during Hurricane Sandy, which ravaged coastal communities in New Jersey and around New York City, the heart of any emergency system is the alternate power source, and if that source is compromised by the effects of the natural disaster, the emergency system is rendered powerless.
There are a handful of NFPA codes and standards that address the topic of emergency power. NFPA 101®, Life Safety Code®, and NFPA 5000®, Building Construction and Safety Code®, provide requirements for emergency power for important building life safety functions such as illumination of egress pathways and marking of building exits. NFPA 72®, National Fire Alarm and Signaling Code, specifies emergency power for the operation of fire alarm systems upon loss of normal building power, and NFPA 99, Health Care Facilities, provides performance requirements for emergency power systems in health care facilities. NFPA 70®, National Electrical Code®, contains installation requirements for the wiring of all emergency systems and standby power systems.
NFPA 110, Emergency and Standby Power Systems, provides construction, performance, and installation requirements covering the emergency power source (typically an engine-driven generator) and the transfer equipment that allows for the designated emergency load to be switched from the normal source of power to the emergency source when the normal source is interrupted. Chapter 4 includes descriptions of two classifications of emergency power supply systems, Level 1 and Level 2. These classifications assimilate well with the requirements in other codes and standards, including NFPA 72, NFPA 99, NFPA 101, and NFPA 5000.
The terms “Level 1” and “Level 2,” however, are not used in the NEC. A careful review of the NFPA 110 descriptions of these two types of systems can help bridge the terminology gap. First, a Level 1 emergency power supply system is described as being “installed where failure of the equipment to perform could result in the loss of human life or serious injuries.” Level 1 systems provide for the most critical of life safety functions. It can be concluded that Level 1 systems align with the systems covered by NEC Article 700, Emergency Systems. A Level 2 emergency power supply system is described as being “installed where the failure of the EPSS to perform is less critical to human life and safety.” Level 2 systems are required in several NFPA codes and standards, and where those requirements are being enforced they become legally required. NEC users are familiar with that term, as it is part of the title of Article 701, Legally Required Standby Systems. It can be concluded that a Level 2 system aligns with the standby power systems covered by NEC Article 701.
This is just an introduction to the discussion of emergency power requirements covered in various NFPA codes and standards. In the next issue of NFPA Journal, I’ll explore some of the specific requirements on emergency power from NFPA 110 and the NEC.
Jeffrey Sargent is a regional electrical code specialist for NFPA.