Common phrases and definitions:

Class: Based on NFPA 110: Standard for Emergency and Standby Power Systems, the class defines the minimum time, in hours, for which the emergency power supply system is designed to operate at its rated load without being refueled or recharged.

Emergency egress: A continuous and unobstructed way to travel from any point in a building or structure to a public way. A means of egress may include horizontal and vertical travel routes, including intervening rooms, doors, hallways, corridors, passageways, balconies, ramps, stairs, enclosures, lobbies, courts and yards.

Emergency power supply (EPS): The source of electric power that has the required capacity and quality for an emergency power supply system.

Emergency power supply system (EPSS): A complete functioning EPSS is coupled with a system of conductors, disconnecting means and overcurrent protective devices, transfer switches 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 electric power.

Fire-rating or fire-resistant rating (FRR): The measurement of a material’s ability to resist the spread of fire or its contribution to fire growth.

Inverter: An apparatus that converts direct current into alternating current.

Level: Based on NFPA 110, this standard recognizes two levels of equipment installation, performance and maintenance. Examples of Level 1 and Level 2 loads can be found in NFPA 110, A.4.4.1 and A.4.4.2.

• Level 1 systems shall be installed where failure of the equipment to perform could result in the loss of human life or serious injuries. Any system that powers egress lighting is a Level 1 system; its failure could result in people being unable to exit a building during, say, a fire.
• Level 2 systems shall be installed where the failure of the EPSS to perform is less critical to human life and safety. An example of this is an emergency lighting unit.

Survivability: The capability of a system or its crew to avoid or withstand a man-made hostile environment without suffering an abortive impairment of its ability to accomplish its designated mission.

Type: Based on NFPA 110, 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.

UL: A safety organization that sets industrywide standards for new products.

UL Guide Information for Electrical Circuit Integrity Systems (FHIT): Contains information to identify the system and its installation limitations to maintain a minimum fire-resistive rating.

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