At Functional Devices, we don’t just build “devices” — we build solutions that keep buildings safe, code-compliant, and installers sane. Since 1969, we’ve been creating relays, controls, and sensors that do their jobs so well you almost forget they’re there… until you really need them.
And when it comes to emergency lighting, UL924 is one of those can’t-ignore codes. But not every UL924 relay is a one-size-fits-all unicorn. In fact, beyond our flagship ESRN, there’s a whole family of UL924-compliant relays that could be the Goldilocks fit for your project. This blog is your cheat sheet to “Every UL924 Relay Other Than ESRN.” Grab a coffee; let’s decode the alphabet soup.
Looking for a specific relay or technical help right now? Check out our UL924 product lineup here or contact our engineering support team; we’re ready to help you spec the perfect device for your project.
Every UL924 Relay (Other Than ESRN)
ESRN: The All-In One Option
Think of the ESRN as the Swiss Army knife of UL924 relays and is Functional Device's most popular UL924 relay. It has automatic load control, which allows you to control the lights on your emergency circuit with the same wall switch and dimming signal as your normal circuit. It has many quality-of-life features for passing inspections, such as test buttons and indicator lights. If you were looking for a single UL924 device that can do everything, the ESRN is a great choice.
When You Don’t Need All the Bells and Whistles
If your only requirement is “lights on in an emergency,” you don’t need to pay for functions you’ll never use. Below are the other players in the lineup.Think of them as ESRN’s leaner, more specialized siblings.
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Relay |
What Makes It Special |
When You’d Choose It |
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ESRN without dimming override |
For projects where you’re fine without dimming override but still want indicators and test buttons. |
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The straight-shooter |
Just shunts around switches and dimmers in emergency mode — nothing more, nothing less. |
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The double-pole dimming specialist |
Perfect for 3-wire dimming circuits that need a solid emergency shunt. |
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The control freak |
Lets one switch handle both normal and emergency circuits during normal operation, then forces full brightness in an outage. |
FAQ: UL924 Relays Beyond ESRN
Q: Do I lose compliance if I don’t use ESRN?
A: Nope. All of these relays are UL924-compliant and will still bring your emergency lighting to full brightness when power fails. The differences are about features, not compliance.
Q: When should I pick ESR2401B instead of ESRN?
A: If you just need a reliable, code-compliant relay without extra features. It’s the “black coffee” of UL924 relays — no frills, but does the job every time.
Q: What is “dimming override” and which relays support it?
A: Dimming override is like the “emergency override button” — it forces full brightness regardless of the dimming state. ESRN supports it; ESRN-1 does not.
Q: My lighting circuit uses 3-wire dimming. Which relay do I use?
A: Grab the ESR01P, which is a double-pole relay designed exactly for that scenario.
Q: I have separate emergency and normal lighting circuits but want one switch to rule them all.
A: That’s the specialty of ESRBE277C — normal mode you control both, and outage mode emergency lights take over.
Q: Can I mix and match these UL924 relays in one project?
A: Sure. Think of them as tools in a toolbox. Use ESRN where you need bells and whistles, ESR2401B where you need simplicity, and so on.
Q: What if I still can’t decide?
A: Give us a shout. We like solving these puzzles and can help you spec the best fit.
Functional Devices: Helping You Navigate UL924 Relays
At Functional Devices, we’re not about forcing you into a single product. We’re about giving you options so you get exactly the functionality you need, without overpaying or overcomplicating your wiring.
Whether you’re wrangling dimming circuits, separate emergency feeds, or just need a no-nonsense UL924 relay, we’ve got a model that’ll do the job and do it reliably. Pair it with our RIB lighting controls, and you’ll maintain the normal control behaviors you want, while always being ready when power fails.
Explore the full UL924 relay lineup or reach out to our team today for more information.