Updated UL924 Standard – What You Need to Know from the TLA Controls Team

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Updated UL924 Standard – What You Need to Know from the TLA Controls Team

Aug 24, 2022 | Controls, Tech Corner

Hi, it’s Carl from the TLA Controls Team, and I’m back with the insights you need now on the changes to the UL924 Standard.

Among the many critical elements of an electrical engineer’s or lighting designer’s job is designing an emergency egress lighting system that is guaranteed to function as intended, when it’s needed, every time it’s needed. Safety, security, and lives may depend on it.

At The Lighting Agency, we take our role in the specification and procurement process of emergency lighting and control solutions seriously by keeping our clients and colleagues informed of significant industry updates and keeping their toolboxes full of solutions to stay on top of the regulatory landscape and keep people safe by designing the right systems.

Updates to UL924 Standard

Speaking of industry updates, are you aware of the recent new language added to the UL924 Standard?

Updates were introduced to the UL924 Standard for Emergency Lighting and Power Equipment, effective May 6, 2022, making a significant portion of the wireless emergency lighting control devices (ELCD) on the market obsolete (more on this in a moment).

Before May 6, 2022, many wireless-type ELCD’s relied on a form of power interruption to indicate when normal power was lost, and the emergency lights needed to activate. This power interruption event or “power blip” was typically assumed to be the handful of seconds after the loss of normal power during an outage, but before the automatic transfer switch completed the transfer to backup power.

An ELCD connected only to the emergency circuit would experience this sudden loss of power and subsequent return of power a few seconds later, and so enter its 100% output emergency mode. Compared to a traditional ELCD or automatic load control relay (ALCR), with a hard-wired normal power sensing circuit, a device like this reduced labor and simplified wiring by eliminating the sensing circuit altogether.

The images below show the difference in wiring between a traditional ALCR device and a power-interruption type device.

Wiring for ER Units showing traditional ALCR with dedicated normal power sensing circuit
Pictured above: Figure A. Traditional ALCR with a dedicated normal power sensing circuit

Figure of wiring for EM Units showing Power-interruption type ALCR requiring a 30ms loss of power

Pictured above: Figure B. Power-interruption type ALCR requiring a 30ms loss of power

The details

Okay, simplifying the field installation is great, but what if the emergency power source is an inverter with a near-instantaneous transfer?

Well, some commercially available inverters include an adjustable transfer delay setting to introduce a power blip and trigger the downstream ELCD.

But what if the inverter doesn’t have an adjustable delay, or the backup power source is a UPS, or the backup power source might be updated in 8 years to something else with an unknown transfer time? Wouldn’t an ELCD that relies solely on the power blipping be a cause for concern in these scenarios?

If you answered “Yes!” then you may have a future on the UL924 Standards Technical Panel! They were also concerned about the risk of misapplication, enough so that they formally rejected this technology and updated the language of the Standard to require – effective May 6, 2022 – that:

  • The ELCD shall be provided with an input signal indicating the presence of normal power.
  • This input signal monitoring feature, which can be wired or wireless, shall be continuously functional and independent of the emergency power feeding through the ELCD to the load.

Most wireless controls manufacturers went back to the drawing board to design and produce a compliant device. Because these changes took effect so recently, most manufacturers are still at the drawing board without a native wireless UL924-compliant ELCD to offer.

UL924 compliant solutions

Acuity is one of the leading few manufacturers who has adapted to these new requirements and offers multiple UL924 compliant solutions for wireless nLight Air.

Solutions include a traditional-style ALCR device with a hard-wired normal power sense circuit, and a wireless-style ALCR with the new wireless normal power sense technology, which allows any normal-powered Air device the ability to be configured as a normal power sensing beacon with the latest firmware.

The figure below shows at-a-glance how this new technology works.

timeline of UL924 compliant solution nLight AIR Group

Pictured above: Figure C.  nLight Air can use a normal-power device to broadcast the presence of power every 8 seconds to wireless emergency devices. If the broadcast stops, emergency lights are activated to full output.

See the nLight Air emergency product page, solutions brochure, or check out this quick video – nLight® AIR Emergency Solution – EM Options – for more detailed information on these leading-edge UL924 compliant solutions.

TLA Controls is here to help

Team TLA and the Controls Department are here to help our local engineering and design community produce high-quality designs and specifications. We’re always ready to share the latest insights into the world of manufacturers and products.

Please do not hesitate to reach out to any of our expert controls sales staff to schedule a Lunch and Learn on code, product, or whatever controls topic you want to learn more about with Rob Pries, Nick Berry, or myself Carl Canfield.

Our Controls Team is here to help. Drop us an email with your requests for future Tech Corner posts!


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Posted in: Controls | Tech Corner