Emergency lighting is lighting that stays on or automatically turns on to facilitate a building’s safe evacuation when it suffers a power outage. There is a trend of using luminaires as both general and emergency lighting, and it presents special control considerations.
Traditionally, emergency lighting design often entailed installing dedicated battery-powered emergency units, such as tungsten-halogen “bug eye” luminaires. These luminaires would provide the average 1 foot-candle of egress path illumination for at least 90 minutes as life safety codes require.
However, these luminaires sit “dark” until needed, detracting from the space’s aesthetics. A growing number of projects eliminate the dedicated emergency light and use the same luminaires for general and emergency lighting, delivering emergency power using battery, backup generator or uninterruptible power supply. Growth in solid-state technology, resulting in proliferation of luminaires with built-in switching and dimming functionality, facilitated this trend. These dual-function luminaires may be subject to automatic/manual control for energy management (energy codes) and visual needs, and the life safety code may require them to automatically activate at full brightness in the event of a power failure.
A variety of codes regulate emergency lighting. The two most prominent codes are NFPA 70, the National Electrical Code (NEC); and NFPA 101, the Life Safety Code. Other codes and standards may apply, including UL 924 (emergency lighting and power equipment), UL 1008 (transfer switches), the International Building Code, the International Fire Code, and NFPA 110 and 111 (standby power systems). Consult the authority having jurisdiction (AHJ) to determine the codes and standards that apply to a given project and how they’re interpreted.
The 2014 NEC added a requirement to Article 700 that directly controlled luminaires used for emergency lighting to be listed (UL 924 certification) for use in emergency systems, which acknowledged use of luminaires that provide both principal and emergency illumination without sacrificing control flexibility. Similar to the 2017 NEC, UL 924 defines “directly controlled luminaires” as having the functionality to automatically override any control setting (e.g., dim, off) and establish an appropriate output illumination level in the event of a power failure.
Anthony Campbell, VP brand management, Hubbell Lighting, said the bypass device must be UL 924-listed, or if the bypass is integral to the control equipment and used on an emergency circuit, that equipment must be UL 924-listed. If a directly controlled luminaire is used on an emergency circuit, it must be UL 924-listed as well. If a device is used to transfer to emergency power in either a feeder or branch emergency circuit, it should be UL 1008-listed.
Michael Brown, product manager, Pow-R-Command Lighting Control, Eaton, said UL 924-listed directly controlled luminaires equipped with integral battery and loss-of-voltage sensing electronics can be controlled by remotely operated two-pole circuit breakers designed to provide power connections for both emergency and normal lighting.
“This application-specific circuit breaker helps engineers design emergency lighting systems that meet NEC Section 700.12 that requires the same branch circuit to feed both emergency power and normal power of the emergency lighting luminaire,” he said.
Other methods for controlling emergency lighting, he added, include using UL 924-listed relays. These devices are typically rated for 20-ampere lighting loads and mounted separately outside of lighting control panelboards or relay panels. UL 924 relays are available in two general models: switching only and switching and dimming. The latter disconnects dimming circuitry to force dimmable egress lighting to 100 percent light output.
“Different manufacturers offer products that are listed to either UL 924 or 1008, and these products act differently from each other,” said Charles Knuffke, Wattstopper Systems vice president and evangelist at Legrand. “It’s absolutely key to be clear in understanding what is required in the wiring and how the product operates.”
Campbell added that it’s not enough to simply review each component’s listing to ensure proper system operation.
“The entire lighting circuit and all contained equipment from the emergency power source to the lighting load—including switches, dimmers, occupancy sensors, photocells, energy management equipment, control signals and all related controls bypass equipment—must be tested to produce code-complying light levels upon loss of normal power, either by transfer, bypass or control system state,” he said.
The AHJ may inspect system operation to ensure it is appropriate. Some manufacturers include a test button to simplify matters.
Overall, the designer must ensure emergency luminaires operate in accordance with life safety codes regardless of how they’re controlled during normal operation. The contractor should ensure these systems are properly installed and operational in accordance with codes, approved plans and manufacturer instructions.