Emergency lighting systems are essential components of building safety. When power fails, these systems must kick in instantly to illuminate exit routes and guide occupants to safety. UL924 relays are designed specifically to meet this need, ensuring that emergency fixtures activate reliably during outages.
At Functional Devices, our range of UL924-compliant RIB® (Relay-In-a-Box®) relays serves this exact purpose: giving engineers, installers, and facility managers versatile, dependable tools for emergency lighting applications. In this guide, you’ll learn what makes these relays stand out in 2026 and which models are most adaptable in the field.
What a UL924 Relay Actually Does
A UL924 relay is more than just a switch. It’s an automatic load control relay designed to ensure emergency luminaires receive full power when normal utility power is lost. It overrides dimming or switching controls and guarantees that life-safety illumination comes on regardless of the position of wall switches or automated lighting controls.
These relays are tested and listed to UL924 standards, which means they meet strict requirements for emergency performance and are suitable for code-mandated life-safety applications.
Key Features to Look For
When evaluating UL924 relays for 2026 projects, here are some capabilities that professionals value:
- Wide voltage input range so the relay can work with both normal and emergency power sources
- Override of dimmers (e.g., 0-10 V systems) to ensure emergency lights go to full brightness
- Remote or local test options for inspections and maintenance
- Multiple mounting styles such as nipple, panel, or ballast channel to fit different installation needs
- Clear status indicators to provide visible confirmation of power states
Notable UL924 RIB® Relays Worth Considering
ESRN — Multi-Voltage Load Control Relay
The ESRN UL924 RIB® Relay is a highly adaptable choice when your installation involves mixed power sources. It accepts both 120 V and 277 V inputs, making it ideal for facilities that operate with varied utility and emergency voltages. You can control emergency lighting as if it were standard lighting, but when normal power is lost, ESRN automatically energizes the emergency lighting.
This model also supports 0–10 V dimming override, lets fire alarm panels trigger emergency circuits via dry contact, and can be wired for remote testing. A built-in test button and LED indicators make commissioning and inspections easier. For details and ordering, see the ESRN product page.
ESRB — Ballast Channel Mount Option
If hardware placement is constrained by fixture design, the ESRB UL924 relay offers a similar suite of emergency features to the ESRN, but mounts inside the ballast channel. This approach saves space and makes the relay an excellent candidate for retrofit work or shallow enclosures. You can find the ESRB and its specifications on its product page.
How These Relays Fit into Your Emergency System
In a typical installation, a UL924 relay is placed between normal lighting controls and the emergency load. Under everyday conditions, the relay lets the lighting system operate as usual, responding to switches, motion sensors, or dimmers. But if utility power is lost, the relay immediately connects the emergency power source—such as a generator or inverter—to the emergency lights, ignoring any control that might otherwise keep them off.
This automatic switching ensures compliance with building codes and life safety standards, giving facility operators peace of mind.
Tips for Installation and Testing
To get the best performance out of your UL924 relay in 2026:
- Wire it according to the application needs, whether bypassing switches, overriding a dimming circuit, or integrating with a fire alarm panel.
- Use the remote test capability or local test button during inspections to verify operation without energizing the entire fixture.
- Choose mounting options that fit the physical constraints of your lighting infrastructure.
Connecting with Functional Devices
Functional Devices offers a broad portfolio of emergency lighting relays and support materials. For guidance on choosing the right model, wiring diagrams, or technical specifications, visit the Functional Devices UL924 relay catalog or reach out to our support team.
Emergency systems save lives. In 2026 and beyond, the right UL924 RIB® relays ensure those systems perform exactly when they’re needed.
For more information on our full line of UL924 RIB® Relays for Emergency Lighting, contact us.