Case study: Specifying a functional and practical emergency lighting system

The Whittingham Discovery Center in Stamford, Connecticut, project was a new, ground-up construction, consisting of approximately 10,000 square feet of exhibit space, educational space, a cafe, an occupiable roof terrace and support spaces, such as offices and back of house areas, across two floors and a basement. The building was in a park, surrounded by existing walking paths and pedestrian spaces. A generator was not provided for this building.

While the building’s size did not prohibit using unit equipment or small, local inverters, the building’s geometry and the limited building technical staff would have made using such power sources challenging for maintenance. The center of the building was a double-high exhibit space through which most of the building’s occupants would egress. Not only was the ceiling height in this space tall, the ceiling was also sloped and had triangular ceiling tiles, with a carefully coordinated reflected ceiling plan.

To preserve the aesthetic of the space, standalone unit equipment, such as bugeye style emergency lighting fixtures, were not an option. Lighting in this space was generally recessed in the ceiling or cove-mounted and was well above a height that was easily accessible with a ladder. Had lighting fixtures been provided with integral battery packs, regular testing and maintenance would have been difficult. Lighting in many spaces was also decorative and was not available with standard battery backup options.

Furthermore, the limited number of maintenance staff warranted a simplification of emergency lighting testing. For these reasons, a central lighting inverter was ultimately specified to provide power to the emergency lighting throughout the building.

The lighting inverter was sized at 3 kilovolt-amperes (kVA) and was selected as a single-phase unit with a single 120-volt (V) input and 12 output circuit breakers at 120 V, 20 A. The inverter was in the center of the building in the basement, with the furthest emergency lighting fixture approximately 125 feet from the inverter.

Emergency lighting was provided where required by code at the egress path, mechanical rooms, electrical room, elevator and public bathrooms. To provide an additional level of safety in an outage, emergency lighting was also provided in each dry lab classroom, the cafe kitchen and single-occupant bathrooms. Emergency lighting was also provided throughout the building exterior and landscape to ensure safe passage from the building to the surrounding park walkways during an outage or fire.

Figure 4: A 10 kilovolt-ampere central emergency lighting inverter with integral circuit breakers and maintenance bypass. Courtesy: Kohler Ronan Consulting Engineers LLC

The lighting controls in the building were done via a combination of wireless standalone controls and a centralized networked system. For the areas with standalone control, such as offices, the kitchen and back-of-house spaces outside of the means of egress, UL 924 emergency lighting bypass relays were used to allow the emergency lighting to be controlled in tandem with the normal lighting and to monitor normal lighting power.

In the spaces where the centralized system was used, such as the exhibit space, dry labs and landscape, the lighting control system monitored normal power via a three-phase voltage sensing input connected to the panelboard serving the spaces and was UL 924 listed. The lighting control system was programmed such that, during normal operation, the emergency lighting zones were controlled to match the normal lighting, but upon sensing loss of power at the panelboard, emergency lighting was put to full brightness.

There was also a fire alarm contact provided to the central lighting control system to bring emergency lighting to full brightness upon an alarm. Because the central processor for the lighting control system was integral to the emergency lighting operation, the processor had to be circuited to the inverter as well. Bypass relays were not used for emergency lighting zones fed from the centralized lighting control system; rather they were fed via dedicated emergency lighting room controllers located in the basement main electrical room adjacent to the inverter.

The design team successfully coordinated and specified a functional and practical emergency lighting system for the building, satisfying the project budget, architectural aesthetics and owner’s operational needs.

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