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Code-Compliant Control of Emergency Luminaires

July 16, 2018

Advances in LED luminaire design now allow for a wide variety of automated and manual control setting adjustments that can save energy, modify room aesthetics, reduce harmful bacteria levels, and even affect occupant health and wellbeing. Lamps have become luminaires, and luminaires are now becoming lighting systems. These lighting systems are sometimes fully contained within a single apparatus or may be distributed over an entire building with sensors, transmitters, relays, receivers, power units, and of course the light source itself. These more complex systems can provide much greater capability to precisely meet the lighting needs of a space as it changes over time and for various uses.

But there is one remaining constant for all of these spaces: when occupants need to leave a facility, especially in case of an emergency, the facility must provide sufficient illumination to help them do so safely and without delay. The Life Safety Code, NFPA 101, requires that a facility provide a minimum level of illumination along the entire means of egress, which is defined as any point in the building to a public way. In response to luminaires incorporating increasingly complex and interactive control features, UL 924, the Standard for Emergency Lighting, has been updated to ensure that the more complex features and controls of modern luminaire systems do not inhibit a luminaire’s ability to perform this fundamental safety function.

Emergency luminaires with control inputs used for dimming, energy conservation, or similar output level management are referred to as “Directly Controlled Luminaires.” A significant advantage of directly controlled luminaires, and the primary driving force for their adoption, is their ability to serve in both normal and emergency mode without sacrificing control flexibility. This reduces the need for normally ‘dark’ fixtures (such as unit equipment) to fulfill emergency lighting needs. The 2014 NEC (National Electrical Code, NFPA 70) added a requirement that directly controlled luminaires used for emergency lighting (within the scope of Article 700, Emergency Systems) be listed for use in emergency systems. This requirement is fulfilled only through certification per UL 924. UL 924 defines directly controlled luminaires as having the functionality to automatically override any control setting (such as dim or “off”) and establish an appropriate output illumination level when loss of normal power is detected.

On May 1, 2018, UL 924 was revised to provide greater clarity for testing directly controlled luminaires and other emergency lighting control devices. The revisions included a significant expansion of Section 47, which was renamed from “Normal Operation Test” to “Emergency Lighting Control Functionality (ELCF) Test.” The purpose of this test is to validate that emergency lighting controls, whether integral to a luminaire (as is the case for directly controlled luminaires) or as a separate device, respond appropriately when the facility experiences a loss of normal power. The fundamental concept behind this test has not changed. The expanded content of clause 47.2 now provides guidance for evaluating each of the five basic “functions” of an emergency power and lighting system:

  • sensing normal power status
  • interpreting a communication signal associated with normal power status
  • controlling a device’s status (e.g., changing it from “off” to “on”)
  • distributing emergency power to appropriately designated loads when normal power is lost
  • simulating loss of power when a ‘test’ function is activated

Not all equipment includes all of these functions, and multiple functions can often be evaluated through a single test. The Section 47 program also requires the tests to be performed in any and every available sequence and to consider whether the individual failure of certain electronic components could compromise the equipment’s ability to respond.

Another addition to the Standard is a new informative Appendix B that describes how ELCF is incorporated into various types of emergency lighting equipment. This appendix includes a description of the “interpretive function” discussed in clause 47.2, which primarily applies to control inputs using proprietary or industry standard communication protocols like 0 – 10V, DALI and DMX512. It also describes the importance of an Emergency Lighting Control Device (ELCD) having a default position that does not inhibit the flow of emergency power when normal power is lost.

The UL 924 evaluation of directly controlled luminaires and other ELCDs used in an emergency lighting system affirms that appropriate lighting performance levels are established when normal power is lost and emergency conditions arise. In this way, UL 924 fulfills the expectation of NEC 700.24 which requires these products to be listed for use in emergency systems.

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