Lighting

Thinking about emergency lighting code compliance

Emergency lighting control takes on many different forms and consulting engineers need to know the required codes and standards as well as the strategies to take to find the best possible solutions

By Ethan Biery October 18, 2021
Courtesy: Lutron Electronics

 

Learning Objectives

  • Become familiar with the different codes and standards associated with emergency lighting and the four key strategies available to meet them.
  • Learn about the emergency lighting control system used to meet both the code requirements and the performance demands of the space.
  • Evaluate emergency lighting strategies and determine whether a centralized emergency control is the best choice for a project and the client’s desired sequence of operations.

In the end, the specified emergency solution must be reliable and comply with all project requirements while still meeting applicable codes (such as NFPA 101: Life Safety Code and NFPA 110: Standard for Emergency and Standby Power Systems). Emergency lighting control must achieve three things:

  1. Get power to the emergency fixture during a utility power interruption.
  2. Force the emergency fixture to a predetermined output level (often, but not always, 100%), bypassing any controls.
  3. Prevent the emergency fixtures from being turned off or bypassed before power is restored.

Understanding desired emergency lighting system functionality

Before settling on a specific control method, it is important to identify the emergency lighting scenarios and preferred sequence of operations in the building. The desired lighting performance, fixtures being used and the design of the emergency power system all factor into the specification of the desired emergency lighting control solution.

First, users need to understand the type of emergency power system being used. If the building does not have a centralized inverter or a backup generator, emergency lighting will have to be distributed, requiring dedicated emergency lights (“bug eyes”) or integral battery backup LED drivers in selected fixtures. While these systems are simple to design and have no impact on any underlying control system, they do require additional fixtures or specialty fixtures, regular testing (manual or automatic) and an awareness of ongoing battery replacement or maintenance requirements. Conversely, if a centralized backup power system is in place, there is no need for battery backup at the fixture level. In this case, the fixtures are fed by a “normal/emergency” feed, which automatically switches between utility power and an emergency source using an automatic transfer switch (ATS).

Next, make sure to consider several additional factors and understand the client’s expectations. Are the emergency fixtures integrated with the general lighting zones or are they on their own control zones? Will the emergency lighting be integrated with the fire alarm system? Is emergency lighting expected to always go to full-on or does the facilities team want to specify different fixture responses for power outage versus fire alarm versus an active shooter or other crisis scenario? In the latter scenarios, for example, it may be desirable to force the lights off to delay intruders. In a fire, users might program lighting to go on to a dimmed level rather than full-on, which can make egress through smoke difficult. A centralized emergency solution can help enable more situation-specific lighting responses.

Utilizing a smart, centralized system versus a stand-alone or distributed solution enables adaptive emergency protocols and more flexible implementation, initially and over time. As the safety expectations of occupants and building owners change, it’s easier to design and adapt a control solution that meets code requirements, meets budget and matches the expected performance. Smart, digital systems can support future functionality as the needs of the space change over time.

Designing to meet emergency lighting codes and standards

To ensure the safety and security of building occupants, emergency lighting must comply with the applicable national building codes. However, writing the best specifications to ensure code compliance may not be as straightforward as it seems.

NFPA publishes codes for the purpose of minimizing the possibility of and negative effects from fire and other risks. NFPA 70: National Electrical Code, NFPA 101 and NFPA 110 are building installation codes, describing design decisions and steps that must be taken to help ensure a safe building. The International Building Code, developed by the International Code Council (ICC), is another example of a building code designed to protect public health, safety and welfare.

UL sets and tests-to industrywide safety standards for new products. UL standards are product-level standards, describing features and functions of individual products within a building to help ensure the building safely operates. UL product evaluations will often focus on whether a product can be installed in accordance with building installation codes such as those published by the NFPA or ICC.

What is the relationship between UL standards and building codes? Building inspectors look for the finished building to meet the requirements specified in the relevant NFPA or ICC code. Using UL-Listed solutions is one way to help meet code and as such lighting engineers may write a design spec that indicates a solution must meet a specific UL standard. But calling out a specific product standard is not always advised, since certain products or combinations of products may be used to meet the code requirements even without everyone meeting the UL standard. While inspectors and other authorities having jurisdiction (AHJs) may expect to see an emergency-specific UL listing, there may be a variety of acceptable UL standards.

It’s a misconception that a product must be marked as UL924 compliant (the standard for emergency lighting and power equipment) to meet the emergency lighting codes, such as those set forth by the NEC. Systems can be designed to meet code without each of the components being marked specifically with a UL924 mark; for example, the NEC calls out a variety of allowable product safety standards that can be used.

Furthermore, the list of allowable standards is expected to be added to in the forthcoming 2023 revision to the NEC. Therefore, when specifications are being written, it is better to reference the required building codes than the specific product standards that can be used to meet them.

Four emergency lighting control strategies

We will now look at four different strategies and address the advantages and shortcomings of each. The following examples start with standalone options that require separate or specialty fixtures, then describe automatic load control relays (ALCR) options that require additional relays and present centralized solutions that use the existing general lighting fixtures to reduce cost, simplify installation and offer more flexible and responsive features. If there’s a generator or inverter in the building, the centralized control scenario is likely to offer the best performance and future proofing at the lowest cost.

Strategy No. 1: Standalone emergency lighting

This is a distributed emergency lighting strategy that may be deployed in three different ways.

  • Dedicated emergency fixtures are powered by a normal/emergency source and are on all the time. When normal power cuts out, the emergency power source takes over. This strategy is often employed in corridors and stairwells.
  • Fixtures powered by emergency power only. These fixtures are off when normal power is present and come on only when normal power is lost.
  • Integrated fixtures that have self-contained batteries (e.g., “bug-eye fixtures”). These fixtures are connected to normal power which is used to charge the batteries. When normal power is present, the fixtures are off and the batteries are charging. When normal power drops out, the fixtures illuminate, powered by the stored battery energy. Unlike the previous two methods, this solution may be used in cases where there is no centralized emergency power.

The emergency-only fixture is a simple, code compliant option. The problem is they are not controlled by a lighting control system. They may require additional fixtures beyond those needed for general-purpose lighting. They are often aesthetically unappealing and less energy-efficient because they may be fully illuminated 24/7 even when a space is not occupied. They offer almost no flexibility, must be regularly tested and fixtures with batteries eventually require battery maintenance or replacement.

Strategy No. 2: General-purpose fixtures with battery backup

In this scenario, certain general-purpose fixtures in the space are designated as emergency fixtures. This means they require an emergency LED driver with integral battery to be installed (one per fixture). When normal power is present, the battery is charged with a constant-hot connection to the emergency LED driver while a separate normal (nonemergency) driver controls the LEDs. When normal power is lost, the normal driver loses power and the emergency LED driver uses the stored energy in its battery to power the LEDs.

Emergency LED drivers are meant to provide enough illumination to satisfy the required footcandle levels for egress; these levels are typically below the full output capacity of the fixture. Battery backup in the fixtures allows the specifier to deliver power using general lighting fixtures. As with emergency-only fixtures, this is a distributed approach that does not enable adjustable emergency lighting levels.

Like the integral emergency fixtures mentioned before, this solution is often used when there is no centralized emergency power source. While these types of fixtures have no impact on the design of a lighting control system, as the normal driver can operate as part of the system, they require regular testing and long-term battery maintenance or replacement (Figure 1).

Figure 1: Emergency LED drivers wiring schematic. Courtesy: Lutron Electronics

Figure 1: Emergency LED drivers wiring schematic. Courtesy: Lutron Electronics

Strategy No. 3: Automatic load control relays (ALCR) and branch circuit emergency lighting transfer switches (BCELTS)

If a central emergency power system is present (generator or inverter), using ALCRs or BCELTS allow standard fixtures to be used for emergency lighting, eliminating dedicated or specialty battery-backup fixtures and allowing integrated control via a lighting control system.

ALCRs are UL924-Listed devices that provide emergency power to lighting loads by bypassing the local control device in the event of a loss of power. In normal operation, the local control dims or switches the load. When normal power is lost, the ALCR bypasses the local control and provides the load with normal/emergency power, forcing it to full and locking out any local control.

There are many variations of ALCRs, with varying configurations and quantities of relays, available from multiple manufacturers. The specific ALCR style will depend on the control type being used and how the emergency power will be designed (for example, will ALL the fixtures on the zone be used for emergency or just some of them?). This strategy does not rely on specialty emergency fixtures, but it does require the purchase and installation of the ALCR relays (Figure 2).

Figure 2: Overview of emergency lighting equipment. Courtesy: Lutron Electronics

Figure 2: Overview of emergency lighting equipment. Courtesy: Lutron Electronics

With certain control types, such as some ELV or phase-adaptive dimmers, bypassing the control is insufficient. In these cases, the power source to the fixture must be switched completely from the control to an emergency feed. In these cases, instead of an ALCR, a BCELTS must be used. BCELTS devices are listed to UL1008, rather than UL924 and are defined in the National Electric Code Article 700.2 as a device connected on the load side of a branch circuit overcurrent protection device (circuit breaker) that transfers only emergency lighting loads from the normal supply to an emergency supply (Figure 3).

In most cases, one ALCR or BCELTS is required for every emergency zone (a separately controllable group of emergency lighting fixtures). Note that either an ALCR (listed to UL924) or BCELTS (listed to UL1008, the same standard used for normal/emergency transfer switches) or a combination of related products may be used to meet the life safety code requirements specified by the building codes.

Figure 3: Branch circuit emergency lighting transfer switch. Courtesy: Lutron Electronics

Figure 3: Branch circuit emergency lighting transfer switch. Courtesy: Lutron Electronics

Selection of the proper ALCR or BCELTS for any application is outside the scope of this article, as there are numerous variations; there are suitable devices that can be used to provide emergency lighting for all the most common control types: switching, phase control dimming, 0-10 V, DALI digital, DMX and certain wireless fixtures. Designers should seek guidance from experienced and trusted sources, such as the ALCR manufacturer or lighting control system vendor. Below are two common examples. Note in these cases the concept of “control” is generic, as it could be a simple wallbox control or a zone in a sophisticated control system.

The first example is a simple case: There is a dedicated control for switching emergency fixtures and a separate control for switching normal (nonemergency) fixtures. The ALCR is a simple normally closed (NC) shunt relay, which has its relay open when normal power is connected. When normal power is lost, the ALCR senses the loss, closes its relay and bypasses the control to force the lights on. However, this requires two separate controls in the space to separately handle the emergency and nonemergency fixtures, increasing cost and complexity (Figure 4).

Figure 4: Line-voltage switches and phase dimmer wiring schematic. Courtesy: Lutron Electronics

Figure 4: Line-voltage switches and phase dimmer wiring schematic. Courtesy: Lutron Electronics

The second example, while more complex, is a common scenario in many commercial lighting cases. This example shows a situation where 0-10 V dimming is being used and there is a single lighting control zone that has a mix of normal and emergency fixtures. The ALCR being used contains two normally open (NO) relays, along with a control input for switching the load. Under normal utility power conditions, all fixtures can be switched by one of the ALCR relays by sensing the control input; the other ALCR relay is held closed to allow pass-through of the 0-10 V control signal. When utility power is lost, the ALCR senses the loss of normal power, closes the switched hot relay that applies power to the fixture and opens the 0-10 V relay forcing the fixture to 100% (Figure 5).

Using an ALCR or BCELTS to meet emergency lighting requirements can be an easy design choice, especially if manufacturers provide guidance and design tools to ensure the proper device is used. These solutions require no long-term maintenance, although they will still be subject to regular testing and verification as part of the emergency system. Some variations of these devices even offer the ability to trigger emergency lighting via a contact-closure from a third-party system, such as a fire alarm control panel (FACP).

Figure 5: Line-voltage 0-10 V dimmers wiring schematic. Courtesy: Lutron Electronics

Figure 5: Line-voltage 0-10 V dimmers wiring schematic. Courtesy: Lutron Electronics

The challenge with an ALCR approach is they always force the emergency lights on to 100% and they do not accommodate varied responses to different emergency situations (utility power loss versus fire alarm versus crisis situation, etc.). They also can add overall hardware costs and wiring complexity to a project because an emergency relay is required for each zone of emergency lighting.

Strategy No. 4: Centralized emergency lighting

A centralized lighting control system is flexible, cost-effective and robust, wherein one piece of equipment senses and activates emergency lighting for large parts of or even the entire lighting system. This is achieved using a central power-loss-sensing device which sends a contact closure signal to a compatible lighting control system. The lighting control system then forces all pre-programmed emergency lights to a pre-defined level (which does not need to be 100%). Like ALCRs and BCELTS, this requires using a centralized emergency power source, such as a generator or inverter (Figure 6).

Using a centralized emergency lighting solution provides many benefits. Like the ALCR and BCELTS solutions, there is no need for specialty or dedicated emergency fixtures; the same fixtures used for general purpose lighting can also be used for emergency lighting. However, unlike the ALCR and BCELTS scenario, no additional relays are required on emergency zones. Furthermore, emergency functionality can be configured via software, such as selecting which fixtures are activated during an emergency and even what light level each emergency zone may go to. Having reduced light levels may allow for use of a smaller generator, while still maintaining the minimum light levels required by code.

Figure 6: Sharing the power-loss-sensing device among multiple controls. Courtesy: Lutron Electronics

Figure 6: Sharing the power-loss-sensing device among multiple controls. Courtesy: Lutron Electronics

Centralized emergency can even be accomplished with wireless lighting control systems. With some implementations, emergency-specific, red-labeled controls are available for inspectors to identify emergency zones.

One additional advance of a centralized system is the ability to provide software-based override-and-lockout functionality for additional crisis situations beyond power loss, thus allowing fixtures to have different responses for different types of emergencies. Users can even program nonemergency fixtures to override-and-lockout in crisis situations where utility power is still present.

The centralized emergency solution is the most future-proof and adaptable option, requiring no investment in additional hardware. Why focus on adaptability? As we learn more about how to best protect and move people in an emergency, safety best-practices are evolving and changing. Centralized emergency control allows users to adjust the system and its programming over time. The system enables software-based changes that can affect how those fixtures respond in either an emergency power situation or separate crisis condition.

All these advantages contribute to a smooth design process and simplify the project by helping ensure the right equipment is selected. Today’s supply chain issues also make it important to get things right the first time – the opportunity to run to the local distributor and switch out product during installation is more challenging than ever.

The right manufacturer makes the design process easier

Emergency lighting systems are a critical part of commercial building design and while traditional emergency lighting options (dedicated fixtures, always-on emergency lighting) are easy to install, integrating emergency lights into the overall control system is a much more cost-effective, flexible and future-proof way to outfit a space. As technologies advance, building owners and tenants expect more robust lighting performance, different sequences of operations and a wider variety of lighting control protocols. This can add complexity to the design of an integrated emergency solution. The right system provider can make a big difference.

Look for a manufacturer that understands these complexities, is committed to helping think through preferred sequences of operation (such as fire alarm and security integration) and is prepared to guide the company using different control and dimming protocols to deliver the desired system performance.

Designing an integrated emergency solution can be seamless when working with a system manufacturer that offers end-to-end solutions for both normal and emergency zones and has the support, technical expertise and design tools to make it easy.


Ethan Biery
Author Bio: Ethan Biery is a senior systems applications engineering leader at Lutron Electronics.