Acuity launches DC system with ease for classroom integration in mind

Acuity Brands, Inc. has launched a low-voltage DC power and digital controls platform that the company says will simplify AC to DC power conversion in lighting systems and minimize power losses.

Developed via Acuity Brands’ Lighting and Controls business, the DC2DC architecture utilizes low-voltage Class 2 cabling and a DCHUB distribution point to reduce the number of installation and maintenance points for the lighting infrastructure. The company also points to native support for tunable white lighting, as well as grouping into zones or controlling individual luminaires, for cost-effective and flexible configurations targeted at classroom environments.

As LEDs Magazine and other Endeavor Business Media publications have covered, improving building efficiency is a deep opportunity for decarbonization and achieving net-zero energy objectives. DC power distribution architectures have been tapped as a solution to power-conversion losses in distributing electricity from the AC grid to the building’s electrical center and on to endpoints, many of which are DC powered today.

As a quick summary for our readers, existing infrastructure has relied on high-voltage AC distribution technology that has not changed significantly for many years and has been stepped down within buildings using transformers, power packs, junction boxes, multiple wire gauges, and conduit to deliver an appropriate amount of power to both wall outlets and direct-wired equipment. However, individual equipment, appliances, and devices used within the structure been engineered over time to draw less current and need not rely on an alternating-current architecture that was designed to balance the electrical load differently to avoid fire risk and overvoltage conditions.

And there are different paths to DC-powered lighting, from Power over Ethernet (PoE) combining data and electrical transmission over Ethernet cabling, to centralized AC-to-DC power distribution technologies such as Digital Electricity (offered by VoltServer) and other low-voltage digital power transmission systems.

Delivering DC

Back to the announcement from Acuity, we were curious about the capacity of the DC2DC architecture and what distinguishes it from another Acuity DC offering, called Modulus, which debuted several years back. Modulus is a Class 1 DC power supply, delivering over 100 VA (volt amperes) — which NEC requires to be installed with conduit between the head end and the luminaire, according to Acuity’s website — and also has a single port with max capacity of 320 VA. The DCHUB device, however, can serve up to 12 outputs with a capacity of 90 VA on each port, depending on the hub selected, according to Michael Montgomery, vice president, Applied Technology Sales for Acuity Brands. The number of fixtures per port may vary according to their rated input wattage.

“Since the input wattages of DC fixtures are nearly 10% less than their AC counterpart, the equivalent of three 33W AC fixtures can be connected to a single port,” Montgomery explained. In a more specific example, he said, “Downlights, which typically are 15W AC, can have six to seven fixtures per port. Higher lumen-output, lay-in fixtures are typically handled at two per port.” Any fixtures over 90 VA are “not good candidates” for DC2DC, he added.

We discussed the role of DCHUB and supporting technology in the DC2DC system, which includes DC-powered LED drivers. Montgomery said the constant voltage supplied by DCHUB is in turn distributed by the individual fixture driver as constant current to the LEDs within the luminaires. The benefits, he said, are multifold.

“[The luminaire-level DC driver] allows us to set the current — and therefore the lumen output — per individual fixture, which allows us to daisy chain fixtures of varying currents and lumen outputs while making the luminaires individually addressable for control zoning purposes,” Montgomery clarified. A remote driver scheme would require a home run per fixture type in order to be programmed for each connected fixture, increasing labor and materials costs, he said.

Furthermore, with white tunable luminaires, “the forward voltage of the LED boards is quite specific, and the overall voltage tolerance is necessarily narrow so that we maintain 2- or 3-step Macadam Ellipse requirements for consistent CCTs,” Montgomery continued. A remote driver architecture would experience voltage drop that could result in unacceptable color shift.

“Also, by programming individual fixture drivers to their necessary current and lumen output, we can eliminate potential mis-wires in the field,” he said. “If someone were to inadvertently wire [a] 1000-lumen downlight to the remote driver programmed for a 4000-lm troffer, with the current set to 1000 mA, you would burn up the LEDs in the downlight…. DCHUB provides constant 57 VDC, so we can wire to any fixture type because each fixture has a driver programmed with the correct milliamp setting.”

Heading to class

Turning to the classroom scenario from the launch announcement, we asked Montgomery what prompted Acuity to target that lighting application. He stated that there is growing interest in white-tunable products for education — “K–12 specifically” — and the ease of installing the DC2DC system, as well as configuring and zoning LED luminaires with two separate CCTs, is a draw when budgets are constrained and skilled labor is more difficult to find.

“I recently spoke with an executive from a large general contractor who told me the number one problem they face in construction today is the lack of skilled electricians,” Montgomery said, which has caused increased installation costs and delays in construction timelines.

“DC2DC architecture has a particular sweet spot in spaces with fewer fixtures of moderate wattage and multiple control zones, [such as the typical classroom,” he said. “Because you can’t run low voltage for long distances due to voltage drop, we can place a DCHUB just outside of or in the middle of a classroom and reach all of the fixtures easily.”

Moreover, he said, “A journeyman electrician can run a trunk line of 277 VAC down the corridor to tap the input of each DCHUB.” Then an apprentice electrician could run color-coded, four-conductor Class 2 cables and easily match them up with fixture connections, all without power packs and conduit (which varies by jurisdiction) — reducing time and expense for the electrical contractor. “Maintenance also becomes simpler for the facility [personnel] because they are dealing with low-voltage power and cabling” with reduced risk of hazards, Montgomery noted.

Luminaires can be controlled automatically via embedded occupancy and ambient light sensors (as shown in the nearby diagram) or by external ceiling-mounted nLIGHT sensors, with daylight control and dimming down to 0.1%. They can also be operated manually with scene presets, on/off, and brightness/dimming control on switch.

CARRIE MEADOWS is managing editor of LEDs Magazine, with 20-plus years’ experience in business-to-business publishing across technology markets including solid-state technology manufacturing, fiberoptic communications, machine vision, lasers and photonics, and LEDs and lighting.

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