As defined in NFPA 70: National Electrical Code (NEC), there are three types of emergency and standby power systems: emergency power, legally required standby power, and optional standby power.
- Emergency power is required by codes for systems whose operations are essential for life safety.
- Legally required standby power is required by codes for systems that are 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 backup where life safety does not depend on the performance of the system.
With these parameters, the need for emergency or standby power is determined and described in either a building code, fire code, and/or referenced standard. Specific requirements for emergency and standby power systems design will vary based on building occupancy type, facility use, critical function, and equipment served.
Emergency systems are defined by NFPA 70, Article 700 as: systems legally required and classed as emergency by municipal, state, federal, or other codes, or by any governmental agency having jurisdiction. These systems are intended to automatically supply illumination, power, or both, to designated areas and equipment in the event of failure of the primary power supply or in the event of accident to elements of a system intended to supply, distribute, and control power and illumination essential for life safety. When primary power is lost, emergency power systems shall be able to supply secondary power within 10 seconds.
Legally required standby systems are defined by NFPA 70, Article 701 as: systems required and so classed as legally required standby by municipal, state, federal, or other codes or by any governmental agency having jurisdiction. These systems are intended to automatically supply power to selected loads (other than those classed as emergency systems) in the event of failure of the primary power source. Legally required standby systems provide secondary power to aid in firefighting, rescue operations, control of health hazards, and similar operations. When primary power is lost, legally required standby power systems shall be able to supply secondary power within 60 seconds, instead of the 10 seconds or less required of emergency power systems.
Optional standby systems are defined by NFPA 70, Article 702 as: systems intended to protect public or private facilities or property where life safety does not depend on the performance of the system. Optional standby power systems are intended to supply secondary power to selected loads either automatically or manually.
The emergency and legally required standby power supply is the source of electric power of the required capacity to carry the connected loads. The supply system is defined as the Emergency Power Supply (EPS) and may include: Storage Batteries, Generator Sets, Uninterruptible Power Supplies (UPS), DC Microgrid Systems, Fuel Cells and/or Separate Utility Power Sources. NFPA 70, Articles 700 and 701 within the fine print notes (FPN) references NFPA 110, Standard for Emergency and Standby Power Systems. NFPA 110 further defines the requirements for the classification of the emergency power supply system (EPSS). The EPSS refers to the secondary power system in its entirety. It includes the EPS, automatic transfer switches (ATS’s), and all control, supervisory, and support devices up to and including the load terminals of the transfer equipment needed for the system to operate as a safe and reliable source of secondary power.
NFPA 110 defines the Class, Type and Level of the EPSS. The Class is defined as the minimum time, in hours, for which the EPSS is designed to operate at its rated load and are designated as follows: Class 0.083 (5min.), Class 0.25 (15min.), Class 2 (2hr), Class 6 (6hr), Class 48 (48hr), Class X (as required by the application, code, or user). The Type defines the maximum time, in seconds, that the EPSS will permit the load terminals of the transfer switch to be without acceptable electrical power and are designated as follows: Type U, (Uninterruptible), Type 10 (10 seconds), Type 60 (60 seconds), Type 120 (120 seconds) and Type M (Manual). The Level defines systems with a direct impact on life safety. The standard recognizes two levels of equipment installation, performance, and maintenance. Level 1 systems are installed where failure of the equipment to perform could result in loss of human life or serious injuries and correspond well with the requirements of NFPA 70, Article 700: Emergency Systems. Level 2 systems are installed where failure of the EPSS to perform is less critical to life safety and correspond well with the requirements of NFPA 70, Article 701: Legally Required Standby Systems.
NFPA 110 only defines systems with a direct impact on life safety. As such, the systems described in NFPA 70, Article 702 (Optional Standby Systems) do not fall under the purview of NFPA 110. NFPA 110 does not state which applications or equipment specifically qualify as Level 1 or Level 2. Provision of other NFPA Standards and Building Codes state the required Type, Class and Level of EPSS system and whether the systems fall under NFPA 70 Article 700 (Emergency Systems) or NFPA 70Article 701 (Legally Required Standby).
Examples of common secondary power systems required by the Building Code and their associated loads include the following:
Emergency / Type 10, Level 1, Systems include (but may not be limited to):
- Means of egress illumination and exit signage.
- Electrically powered fire pumps (where secondary power is required).
- Elevator cab lighting.
- Emergency voice/alarm communications systems.
- Automatic fire detection systems.
- Fire alarm systems.
Legally Required / Type 60, Level 2, Systems include (but may not be limited to):
- Ventilation for smokeproof enclosures.
- Smoke control systems.
- Jockey Pump (NFPA 101 for high-rise buildings).
- Air Compressors serving Dry and Pre-Action Sprinkler systems (NFPA 101 for high-rise buildings).
- Power and lighting for the fire command center.
- Emergency responder radio coverage systems.
When specifying, reviewing or installing emergency power and standby power systems the requirements of NFPA 70, NFPA 110, other referenced NFPA Standards and the applicable Building Codes need to be taken into consideration to not only verify the proper equipment is connected to the proper secondary power system, but also that the EPSS is rated for the correct Class, Type and Level. If you have any questions, please do not hesitate to contact us at firstname.lastname@example.org.