How to specify emergency lighting controls under new standards

Lighting control insights

• The evolution of lighting controls has streamlined energy efficiency and safety in buildings, integrating emergency lighting systems with modern technology to enhance both functionality and aesthetics.
• While traditional methods like continuously illuminated “night lighting” have been effective, contemporary lighting control systems offer more sophisticated solutions.

Lighting controls have revolutionized energy efficiency, user experience and architectural expression. Occupancy sensing, daylight harvesting, dimming, color temperature tuning, individual luminaire addressing and third-party system integration are some of the countless advancements since the invention of the light switch by John Henry Holmes in 1884. While it can be easy to focus on these exciting advancements, occupant safety and code requirements cannot be overlooked.

The need for emergency lighting is common in today’s built environment. Various International Code Council (ICC) building codes, NFPA standards and Underwriters Laboratory (UL) standards have been adopted that address these needs so occupants may safely exit a building during a power loss.

A simple and robust approach has been to provide continuously illuminated “night lighting” connected to the emergency electrical system, yet this approach wastes energy, may be unsightly and may overuse luminaires. Modern lighting controls provide a more elegant and automated approach to synchronize emergency lighting control with normal lighting, allowing for a homogenous look, energy savings and an improved user experience without compromising safety.

Though each application is unique, this article overviews a pragmatic strategy to integrate emergency lights with modern control systems that may be relevant to common scenarios.

Changes in emergency lighting codes

Effective May 6 2022, there was added language to UL 924 requiring emergency lighting control devices (ELCDs) to monitor the “branch circuit associated with its controlled loads.” This is a change from the 2020 language that requires ELCDs to, “monitor the input signal referred to in 47.2(c) for the branch circuit associated with its controlled loads.”

Figure 1: An example of a listed ELCD. The scale of the device and threaded hub permits straightforward installation into a standard one-half inch knockout. Courtesy: HDR, Inc.

This added language is significant as it closes a gap among various emergency lighting control code requirements and product listings. An exhaustive review and interpretation of these code requirements is outside the scope of this article, but specifiers and facility owners should understand these requirements when evaluating a lighting control system.

Long standing UL 924 interpretations allowed lighting control manufacturers to obtain listings when normal power from the utility or a panelboard was monitored instead of from the branch circuit. Due to this updated UL language, products not monitoring the normal branch circuit can no longer be listed and cannot be used to automatically control emergency lighting, in accordance with NFPA 70: National Electrical Code (NEC). It is important that the emergency lighting controls are evaluated against code and listing requirements to ensure a safe and effective design.

2021 NEC language:

700.26 Automatic Load Control Relay. If an emergency lighting load is automatically energized upon loss of the normal supply, a listed automatic load control relay shall be permitted to energize the load. The load control relay shall not be used as transfer equipment.

Emergency lighting recommendations

The following recommendations are applicable where emergency lighting is desired to be synchronized with adjacent normal lighting (i.e., either dimmed or switched together as a single “zone”). This strategy is common in public spaces such as lobbies, large conference rooms, ballrooms, public corridors or other applications where unswitched emergency “night lighting” would be unsightly or prohibitive. The authority having jurisdiction should be consulted to verify local requirements.

Several manufacturers offer properly listed products to automatically control emergency lighting with adjacent normal lights. These devices “listen” to both normal branch circuit availability and control input to synchronize normal and emergency lighting control. With these products, the emergency lights are always powered by the emergency electrical supply and the lighting control system wiring is separated by dry contacts within them. Upon loss of normal branch circuit power, these devices automatically latch closed and disconnect the control input, raising the emergency lights to full output, regardless of local switch, dimmer or control position.

Figure 2: Example of annotating common control of normal and emergency lights (zone ‘a’). Magenta highlights for normal lighting and yellow highlights for emergency lighting are provided by the author for emphasis. Courtesy: HDR, Inc.

Many products are available that are agnostic to the lighting control system, yet careful selection is necessary to ensure compatibility with the desired control protocol. Figure 1 depicts an example device intended for a ceiling plenum installation adjacent to a remote lighting controller.

Additionally, several lighting control system manufacturers offer proprietary solutions. Though each manufacturer’s solution is unique, it’s critical to verify that each component is individually UL924 listed and that the overall system meets International Building Code (IBC) and NFPA performance requirements.

Based on the revised UL language, these devices can be tricky to specify and confusing to evaluate during the submittal review process. Following is a strategy to assist the design and construction teams in providing a compliant solution:

• On the lighting plans, annotate lighting control zoning to include common control of normal and emergency lighting. Figure 2 depicts a generic example where lighting symbol subscripts indicate common zoning.
• Supplement emergency lighting control zoning with a schematic of a UL924 listed product. This diagram is useful for electrical contractors to understand the design intent and the obligation of providing individually listed products. During submittal review, this diagram is used as a basis of design for evaluation. Figure 3 depicts an example schematic.

Analysis of the code

NEC article 700.26 permits listed controls to automatically energize emergency lighting upon loss of normal power. This practice is common and familiar among lighting control system manufacturers, electrical contractors and inspectors. Each lighting control manufacturer’s solution varies from localized ELCDs to systemic “head-end” strategies, either wired or wireless. Of concern is each product’s UL labeling and compliance with the emergency lighting performance requirements described in the IBC and NFPA 101.

Some manufacturers rely on a “phase loss” device that monitors normal utility or panelboard power and transmits a signal to activate a systemic emergency override sequence. In these systems, if a normal phase becomes disconnected due to a fault or utility outage, designated “emergency” relays are automatically latched closed and any dimming is reset to full output or other preprogrammed level.

Figure 3: Example UL924 listed ELCD schematic. A sequence of operation and clarifying notes reinforce a code compliant design intent. Courtesy: HDR, Inc.

Previous UL 924 language permitted these lighting control systems, “phase loss” devices and “emergency” relays to be individually listed because UL’s previous requirement to monitor normal power was interpreted as normal utility or panelboard power. Though previously compliant for UL, this “head end” monitoring disregards potential faults at a branch circuit, posing a safety hazard. Additionally, this strategy does not meet the emergency lighting system performance requirements described in NFPA 101 and by the IBC since normal power serving individual spaces is unmonitored. The updated UL requirement for ELCDs to monitor the “branch circuit associated with its controlled loads” aligns product listing requirements with these other IBC and NFPA requirements.

Lighting control system manufacturers have been forced to react by removing the UL924 listing from their systems where the associated normal branch circuit is not monitored. However, these systems remain marketed as having been evaluated by UL or meeting the intent of UL924 without specific listing or labeling, which can be misleading and confusing. Regardless, to meet the NEC, each device controlling emergency lighting must be listed and labeled by a nationally recognized testing laboratory such as UL.

Continuously illuminated “night lighting” has been a tried-and-true method to meet the IBC and NFPA emergency lighting requirements. Fortunately, modern lighting control systems can incorporate ELCDs capable of synchronizing normal and emergency lighting control for improved aesthetics, efficiency and user experience. Revised language in UL Standard 924 adds specific listing requirements for ELCDs to monitor normal lighting branch circuits, not the overall utility or panelboard. Specifiers should carefully evaluate their application’s emergency lighting control strategy to verify each component controlling emergency lighting is UL924 listed and labeled, and the overall performance meets IBC and NFPA requirements.

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