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Standards for Backup Power

Backup power systems are subject to multiple codes that can be daunting to learn. Multiple industry codes specify actions for the design, operation, maintenance, and testing of backup power systems and equipment. This article summarizes key codes and standards and provides an overview of their coordination.

The following table describes the focus of the relevant codes.

NFPA 101 - Life Safety Code

One of the most important and basic needs is to minimize the opportunity for fire in buildings and to provide occupants with safe egress should a fire occur. The purpose of NFPA 101 – Life Safety Code is to “provide minimum requirements, with due regard to function, for the design, operation, and maintenance of buildings and structures for safety to life from fire. Its provisions will also aid life safety in similar emergencies.” In the standard, readers find guidance for minimizing the dangers of smoke, heat, and gases; design of safe egress for occupants; protecting occupants from the effects of hazardous material emergencies; and providing emergency communications of fire events.

NFPA 101 does not address “general fire prevention or building construction features that are normally a function of fire prevention codes and building codes”. Nevertheless, it does specify measures in accordance with its primary intent, and several of these measures require backup power. These include smoke detectors, alarm systems, communication systems, emergency signage, emergency evacuation elevators, emergency lighting, sprinkler or other fire-control systems such as fire pumps, and smoke control systems, which are all necessary for safe egress during a fire or other similar emergency. These systems do not always require connection to a backup power generation system – for example, emergency lighting can be powered by batteries. Nevertheless, NFPA 101 contains numerous backup power references to NFPA 70 - National Electrical Code and NFPA 110 - Standard for Emergency Power and Standby Power Systems. An understanding of the coordination of these requirements can be valuable to backup power professionals.

NFPA 70 - National Electrical Code

The National Electrical Code, or NEC, governs electrical equipment installed in buildings. It’s also the primary code that local authorities use to approve installations of electrical equipment and systems. For backup power systems, Articles 700, 701, and 702 are of particular interest. Article 700 specifies that power distribution circuits in regulated facilities be segregated into circuits for Emergency, Legally Required, and Optional Standby loads according to the figure below.
In the most general of terms, Article 700 includes requirements for systems needed to get people safely out of a building in an emergency, and Article 701 includes requirements for systems needed to safely restore building function and occupancy. Article 702 specifies requirements for optional loads such as those used to maintain operational continuity.

Article 700 is the most expansive of the three articles. Requirements for emergency power systems include:
  • Periodic maintenance as well as testing under load (700.3.)
  • A secondary power source for use when the primary backup power source is taken offline for service (Also 700.3)
  • Emergency system equipment must be suitable for the available fault current (700.4)
  • Transfer equipment must be automatic, listed, and marked for emergency use (700.5)
  • Backup power shall be available to emergency systems within 10 seconds of the occurrence of an outage (700.12)
Separately, Article 708 addresses backup power for Critical Operating Power Systems. It requires an assessment of risks to reliable electrical power at certain facilities or portions thereof that supply services necessary for public safety or national security, then developing a strategy to mitigate those risks. Article 708 provisions can apply to facilities such as public emergency call centers, government buildings, key financial data centers, and facilities located along public evacuation routes. Article 708 provisions could also apply to certain hospital operations.

UL 1008 – Standard for Safety – Transfer Switches

NEC Articles 700 and 701 require the use of listed transfer switch equipment, and UL 1008 is the primary standard by which transfer switches are listed. UL 1008 specifies safety and endurance criteria for transfer switches, which manufacturers typically verify through in-house or third-party testing. Following Underwriters Laboratories’ review of satisfactory test data, it lists the equipment for use.

UL 1008 is the standard by which switch Withstand and Closing Ratings are verified, ratings needed to specify transfer switches that can withstand available fault currents as the NEC requires. UL 1008 endurance testing is among the most stringent of available standards. For more information, review ASCO documents entitled UL1008 Transfer Switch Withstand and Closing Ratings and Performance Testing for Transfer Switches. For many other regions of the world, IEC 60947 - Low-Voltage Switchgear and Controlgear provides transfer switch safety and endurance criteria.

NFPA 110 – Standard for Emergency Power and Standby Systems

NFPA 110 specifies requirements for the performance of emergency and standby power systems. It classifies these systems according to the minimum amount of time that they must be capable of providing power. It also stipulates the maximum amount of time allowed to bring secondary power online when outages occur on the primary source. Of note, Chapter 8 provides requirements for routine maintenance and operational testing. These requirements are widely referenced by other NFPA documents and other standards that apply to backup power.


NFPA 99 – Health Care Facilities Code

The Health Care Facilities Code specifies requirements for nearly every area of medical facility operation. Topics range from infection control practices to information technology systems to medical gas management. Several articles refer to NFPA 110 to require that alternate power sources provide power within 10 seconds of the occurrence of an outage of the primary power source. If the 10-second criterium is not met during monthly tests, this capability must be confirmed annually. For more information, review the ASCO document entitled Testing Hospital Backup Power Systems.

NFPA 70 – NEC Article 517 - Health Care Facilities

While the NEC has already been described, it’s important to note that certain of its provisions apply specifically to installation of power distribution systems in medical facilities. These systems can serve loads with particular concerns, such as procedures conducted in areas that could become wet, power where hazardous medical gases are present, and isolation of power supplied to operating rooms. Because patients can be connected to electrically powered equipment for monitoring, diagnostics, and treatment, this standard addresses grounding measures to reduce corresponding electrical hazards.

Article 517 defines and addresses Essential Electrical Systems, which are comprised of Equipment, Life Safety, and Critical Branches, each served by one or more dedicated transfer switches where continuous load exceeds 150 kVA. Article 517 also addresses how to locate important electrical equipment to reduce risk and specifies provisions for load equipment. An Essential Electrical System is shown below.
The Joint Commission Hospital Accreditation Standards

The Joint Commission is the leading hospital accreditor in the United States. Its Hospital Accreditation Standards specify a standard of performance for some aspect of operation, then lists Elements of Performance that someone could use to confirm that the facility is meeting the standard. For instance, Standard EC.02.05.07 – “The hospital inspects, tests, and maintains emergency power systems” - can be confirmed by the types of evidence described in Elements of Performance for EC.02.05.07. This includes Elements 5 and 6, which list monthly testing of the Emergency Power Supply System for at least 30 minutes at required levels of output. If an auditor cannot locate this evidence, the facility is non-compliant on that matter. The standards do not necessarily provide new requirements, rather, they often reference other standards such as those already listed in this document.

The Joint Commission or other authorized organizations audit hospital compliance to grant accreditation, then periodically reevaluate whether it should be maintained. Failure to comply can result in non-accreditation. Because payors such as government agencies and insurers may require accreditation as a condition of payment for services, compliance with standards is important for maintaining revenue streams. In the USA, the Centers for Medicare and Medicaid Services is one of those payors.


Key industry codes and standards include the National Fire Protection Agency’s Life Safety Code, Standard for Emergency Power and Standby Power Systems, Health Care Facilities Code, and National Electrical Code, as well as Underwriter Laboratory’s Standard for Safety – Transfer Switch Equipment and The Joint Commission’s Hospital Accreditation Standards. These documents set forth important provisions regarding the configuration, operation, maintenance, and testing of backup power systems, provisions that are among best practices in the industry. Because there are many cross-references between these standards, industry professionals can benefit by understanding the coordination of requirements between the documents.


NFPA 101: Life Safety Code. 2018 Edition. Quincy, MA: National Fire Protection Association, 2017.

NFPA 70: National Electrical Code. 2020 Edition. Quincy, MA: National Fire Protection Association, 2019.

UL Standard for Safety for Transfer Switch Equipment. Eighth Edition. Northbrook. IL. Underwriters Laboratories, Inc. 2014.

NFPA 110: Standard for Emergency and Standby Power Systems. 2019 Edition. Quincy, MA: National Fire Protection Association, 2019.

NFPA 99: Health Care Facilities Code. 2018 Edition. Quincy, MA: National Fire Protection Association, 2017.

Hospital Accreditation Standards. 2019 Editions. Oak Brook, IL. The Joint Commission, 2019.

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