What Is an Emergency Backup Driver?

Providing adequate lighting during a power outage ensures that occupants and emergency personnel can safely navigate the building. For this reason, many national and local codes have strict regulations that require emergency lighting backup systems in commercial and public buildings. Emergency backup drivers are one common example of these emergency systems.

An emergency backup driver supplies regulated backup power to LED light fixtures during a power outage. Backup drivers continuously monitor the power line for disruptions so that in the event of a power failure, they can automatically switch power from the main supply to the battery. These devices must provide at least 90 minutes of emergency lighting, as required by the National Fire Protection Association (NFPA). Emergency drivers are designed to continuously charge their batteries while the main power supply is operational. As long as the driver receives constant AC power, it will stay fully charged.

The National Fire Protection Association (NFPA) Life Safety Code 101 lists requirements for emergency lighting systems, including emergency drivers. These requirements are listed in NFPA 101 Section 7.9 under the following three subsections.

This section specifies the types of buildings that require emergency lighting systems. These include, but are not limited to, all buildings required by Chapters 11 through 43 of the Code, underground structures listed in Section 11.7 of the Code, and all high-rise buildings required by the Code. This section also states that the energy change between the main power line and the battery backup must not last more than 10 seconds.

Section 7.9.2 requires that emergency lighting systems must always be in operation or be automatically turned on. Emergency drivers must provide at least 90 minutes of backup power. Initial illumination must average 1 ft-candle but no less than 0.1 ft-candle along the floor level of the egress. At 90 minutes, emergency lighting must average 0.6 ft-candle but no less than 0.06 ft-candle at any distance along the egress. 

This section also mandates that emergency backup battery systems be listed to UL 924 Standard for Emergency Lighting and Power Equipment. UL 924 sets forth performance and testing standards for emergency lighting systems. All emergency backup drivers from DiodeDrive are UL-listed to meet these NFPA Life Safety Code requirements.

Finally, Section 7.9.3 of the NFPA 101 details the periodic testing of emergency lighting equipment, which varies depending on the specific type of equipment. Most LED emergency drivers are considered “self-diagnostic battery-operated emergency lighting equipment,” and testing for these devices must be conducted at least every 30 days for at least 30 seconds. A visual test shall also be conducted no less than once every 30 days, and annual functional testing must last at least 90 minutes. A status indicator on the driver should clearly show testing failures.

Backup drivers must be rated for the main line's input voltage, have an output voltage that meets that of the light fixture, and be compatible with that fixture’s dimming type (if the light is dimmable). These specifications will typically be the same as those of the existing driver.

Emergency drivers usually provide a lower wattage to dim the lights’ output under backup power. However, you must make sure the driver has a wattage rating suitable for the lights it will power. High-wattage lights will require a higher-wattage emergency driver, and vice versa for low-wattage lights.

Certain battery backups made for specific types of lights. Troffer and flat panel lights require slim or compact drivers that fit in the light’s profile. Single-point hanging lights, such as UFO high bays, can hang from their specialized driver instead of storing the driver in the fixture housing. Backup drivers for troffer lights often have their own separate LED array that illuminates during a power outage instead of the lighting fixture. These battery backup lighting kits can also be installed in standard fluorescent tube light fixtures needing to meet compliance codes.

UL 924 requires emergency lighting to have manual testing switches for regular testing. There are a variety of test button options available based on the fixture and mounting location. Wall-mounted test indicators, ceiling-mounted test indicators, and test buttons integrating into the light fixture allow for easy testing of emergency systems. Emergency backup kits for high bays and highly mounted lights commonly come with a remote-controlled testing button that allows you to test the emergency system without needing a ladder or scissor lift to access these fixtures.