Emergency Power Systems

For many years there were no accepted standards for the design of emergency and standby power systems, even though these systems have been in use since World War II. Recognizing this need, NFPA formed the Technical Committee on Emergency Power Supplies in 1976. Although the committee developed a report proposing adoption of NFPA 110: Standard for Emergency and Standby Power Systems, it wasn’t until the 1984 NFPA Fall Meeting that the document was adopted as a standard and became the 1985 edition.

Today emergency and standby systems are used to provide backup power for building systems to provide assurance that life safety systems and critical equipment can maintain their operation during a power outage. The use of these systems almost comes as second nature when designing large, complex facilities. Yet, how well do you know the specific requirements for these systems? Questions we must consider include:

In general terms, as defined in NFPA 70: National Electrical Code (NEC), there are three types of emergency and standby power: emergency power, legally required standby power, and optional standby power. Emergency power is required by codes for systems whose operations are essential for safety to human life. Legally required standby power is required by codes for illumination and power equipment that is not categorized as requiring emergency power, but whose failure could create hazards or hamper rescue or firefighting operations. Optional standby power is not required by code and provides equipment whose failure will not impact life safety.

The basic requirements for where the provision of an emergency and standby power is necessary come from the building and fire codes. Whether the local jurisdiction follows NFPA 5000: Building Construction and Safety Code, NFPA 1: Fire Code, NFPA 101: Life Safety Code, the International Building Code (IBC), or the International Fire Code (IFC), the requirements are reasonably consistent. Each of these codes broadly defines the fire, life safety, and critical operations power systems (COPS) that require emergency and standby power systems. While the building codes primarily deal with requirements for new or remodeled buildings, the requirements of the fire codes and NFPA 101 may also apply to existing buildings, as such there may be retroactive emergency and standby power issues to be addressed under these documents.

Specific requirements for emergency and standby power will vary based on building occupancy type, facility use, and critical function. With these parameters, the need for emergency or standby power is determined and described in either a building or fire code. For example, the 2009 IBC requires emergency power for:

While the 2009 edition of the IBC and NFPA 5000 have similar requirements for emergency and standby power (such as high-rise buildings and healthcare facilities) there are some requirements that differ slightly. Some of these differences include:

NFPA 5000 identifies elevators in towers that are used as a second means of egress, in such buildings, the elevator equipment, communications, machine room cooling, and controller cooling all must be provided with normal and standby power Also in NFPA 5000, in buildings more than 120 ft in height, a first responders use elevator must be provided that is served by standby power. NFPA 101 and NFPA 99

NFPA 101 and NFPA 99 are two principal documents widely used in the design of healthcare facilities. While NFPA 101 covers all classifications of building occupancy use, NFPA 99 specifically addresses healthcare facilities.

The 2009 edition of NFPA 101 presents basic requirements for emergency lighting in Section 7.9. Emergency power systems for emergency lighting are to comply with the 2005 edition of NFPA 110. Stored electrical energy systems are required to comply with the 2005 edition of NFPA 111: Standard on Stored Electrical Energy Emergency and Standby Power Systems. Each of the occupancy chapters identifies whether emergency lighting is required in that occupancy.

High-rise building requirements in NFPA 101 are presented in Section 11.8. Among the requirements are the need for the installation of automatic suppression, fire detection, alarm, and communications systems. To provide assurance that these systems will be available in a fire emergency, emergency and standby power are required. The system is to be in accordance with NFPA 110 to serve the electric fire pumps, emergency command center equipment and lighting, elevators, mechanical equipment for smokeproof enclosures, and mechanical equipment serving the smoke control systems.

While emergency and standby power requirements are found in several other occupancy use areas, the healthcare occupancies have the most detailed requirements. NFPA 101 provides the overall requirements where fire detection, alarm, and suppression systems are required, where emergency lighting is required, and other basic fire and life safety needs. However, when it gets to the details of what specific systems need to be served by what level of power reliability, NFPA 99 takes the lead.

The 2009 edition of NFPA 99 identifies three classifications of essential electrical equipment categories based on the level of criticality of the systems served:

The life safety branch is defined as:

A subsystem of the emergency system consisting of feeders and branch circuits, meeting the requirements of Article 700, of NFPA 70 and intended to provide adequate power needs to ensure safety to patients and personnel, and that is automatically connected to alternate power sources during interruption of the normal power source.

The life safety branch of the emergency system provides the emergency power for:

The critical branch is defined as:

A subsystem of the emergency system consisting of feeders and branch circuits supplying energy to task illumination, special power circuits, and selected receptacles serving areas and functions related to patient care and that are connected to alternate power sources by one or more transfer switches during interruption of normal power source.

The critical branch may be divided into multiple branches. The critical branch is dedicated for use in powering specific circuits related to patient care and includes the following:

In order to be able to meet the time requirements of these two essential equipment categories, it is typically necessary to have some combination of stored power and generator power solution.

The equipment system is defined as:

A system of circuits and equipment arranged for delayed, automatic, or manual connection to the alternate power source and that serves primarily 3-phase power equipment.

The equipment system is allowed to serve the following delayed-automatic or manual connection to the alternate power source:

Fire codes

While the fire codes are companion documents to the building codes, remember that the fire codes are an occupancy and use enforcement document, not a construction enforcement document per se. As such, it is unusual to find requirements in a fire code that would require a new system to be installed in an existing building under a fire code. The typical requirements of a fire code will be to maintain the systems in the building that were required under the version of the code followed when the building was first built. Exceptions to this distinction would include:

Substantial changes made in building construction, occupancy, or use after the adoption of the code Existing buildings, structures or operations that were not legally in existence prior to adoption of the code Specific hazardous conditions when specifically addressed by the code Existing facilities that have been identified as constituting a distinct hazard to life or property. With this basic differentiation, the following are some of the primary fire code implications for emergency and standby power.

Since the primary focus of both NFPA 1 and the IFC is on assuring that fire protection and life safety equipment is properly maintained, it should come as no surprise that both documents require building owners to keep up to date records on inspection and maintenance of their emergency and standby power.

In Section 604 of the 2009 IFC, requirements for emergency power systems are delineated. The section is consistent with the requirements of Section 2702 of the IBC and requires compliance with the 2005 NFPA 110 or the 2005 NFPA 111 where emergency and standby power systems are to be installed. The required locations and systems include emergency voice and alarm communications systems for assembly occupancies, smoke control systems, exit signs, means of egress illumination, accessible means of egress elevators, horizontal sliding doors, membrane structures, semiconductor manufacturing facilities, and several other facilities. It further requires stationary emergency and standby power systems to be in compliance with the 2004 edition of UL 2200: Standard for Stationary Engine Generator Assemblies.

In the 2009 NFPA 1, Section 11.7.3 covers emergency and standby power requirements. Section requires compliance with the 2005 NFPA 110 for stationary generators while Section 11.7.4 requires compliance with the 2001 NFPA 111 for stored electrical energy and standby power systems. Emergency lighting requirements are in Section 14.13. This section refers to NFPA 101 for specific facilities requirements.