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Line-Voltage Occupancy Sensors Provide Individual Fixture Control Option in Hi-Bay Lighting Retrofits

Originally published in the June 2008 issue of TED Magazine

Warehouse application for line-voltage occupancy sensors

Acuity Brands Lighting, the parent of Lithonia Lighting, installed the company’s I-Beam fluorescent hi-bay fixtures with sensors in one of its warehouses, generating significant energy cost savings.

Retrofitting standard metal halide hi-bay fixtures to fluorescent hi-bay fixtures can generate energy cost savings of about 50 percent. How does reducing the resulting energy consumption by another 30+ percent sound—made possible by switching to fluorescent?

While tapping what remains arguably the hottest lighting retrofit market, distributors should understand the full advantages of fluorescent over probe-start metal halide, such instant-on and re-strike, which enables the use of switching strategies typically not practical with HID light sources.

Example: An occupancy sensor installed in each fixture senses a lack of occupancy in the area, or a photosensor senses high light levels due to daylight contribution, and either switches off the fixture or its outboard lamp. This provides a choice of energy savings and, if desired, flexible selection of light levels.

An additional 30-80 percent energy savings using occupancy sensors and 10-30 percent savings using daylighting controls can be achieved in a hi-bay fluorescent upgrade, says John Ireland, OEM channel manager for Watt Stopper/Legrand.

Mike Connolly, market development manager for Lithonia Lighting – Industrial Products, says inboard/outboard switching—achieved by separating circuiting ballasts within the same fixture, enabling 0/50/100 percent and 0/33/66/100 percent lamp output/power—is an inexpensive way to gain the benefits of flexibility from the lighting system. “For example, in a gym, light levels can be lowered for school productions or other needs outside of athletics,” he says. “Multi-lamp fluorescent fixtures offer many light level possibilities for user control, daylight harvesting and other applications.”

Occupancy sensing is the predominant strategy, particularly in applications such as distribution centers, warehouses and bulk storage areas. “Any area of 50 percent or less usage levels will accelerate the project’s payback period—even with relatively modest electric rates of $0.07 per kWh,” says Connolly. To optimize lamp life, particularly when the fixtures have high switching activity—more than six on/off cycles per day—programmed-start ballasts and a minimum 15-minute sensor time delay are recommended.

Passive-infrared (PIR) technology is standard in occupancy sensors used in hi-bay applications. “Besides its low cost, most spaces in hi-bay applications are within the line of sight of the sensor, large motion is usually being detected, and little adjustment is required after installation,” says Tom Leonard, director, marketing and product management for Leviton Lighting Management Systems. In hi-bay applications, the sensor may have a lens that provides 360-degree coverage for open areas or a narrow linear coverage for warehouse aisles.

Traditionally, control in such spaces were configured into zones for occupancy sensor or time-of-day scheduling, requiring external power packs and low-voltage wiring. Following market preference for low-cost control solutions, occupancy sensor manufacturers such as Watt Stopper/Legrand, Leviton and Sensor Switch began offering line-voltage occupancy sensors. These sensors mount directly onto light fixtures, sold either through the fixture OEM as an integral component or purchased as a separate item and field-installed by the contractor.

“This enables the lamps in the fixture to be controlled by the sensor, and no additional control wiring is needed for ganging together fixtures into control zones,” says Ireland. “As a result, integral sensors reduce installation time and material costs. This makes for a faster return on investment on your projects, while also reducing the use of additional resources like copper wire. This is a more practical and sustainable approach.”

With no control wiring, these sensors are positioned as a natural for retrofit applications—included in the fixtures being sold into a current project, or sold as an additional upgrade into previous projects that did not include controls. By installing one sensor per fixture, layout and application are greatly simplified, says Leonard, and there are no zoning or re-zoning concerns, as each fixture becomes an individually controlled source.

He adds: “For the distributor, fixture-mounted hi-bay sensors require the least amount of technical value-added services and have some of the highest potential volume opportunities. The opportunity is huge, the technical and engineering support required is minimal, and many utilities are subsidizing their installation.”

Connolly also points out that individual sensors eliminate external controls hardware, making the fixture a self-contained lighting and control system that is more responsive to actual usage. “For example, if a forklift only goes a quarter of the way down an aisle, the other fixtures remain off, providing significant savings,” he says.

The highly granular degree of control, which each fixture responding individually to local conditions, presents interesting possibilities for daylight harvesting in applications receiving significant daylight contribution from apertures such as skylights. (In new construction projects in California, the state’s Title 24-2005 energy code requires daylighting controls in certain big-box spaces.) Ireland says while mounting a photosensor in each fixture is a simple, low-cost solution, it isn’t best practice: “The best way to accomplish daylighting control in a hi-bay application is to have daylighting control zones that match the daylight distribution; this typically results in using one photosensor in the skylight to control multiple fixtures as best practice.”

Leonard points out that an integral photosensor’s true utility within a hi-bay fluorescent fixture may not be actively turning the lights on and off, but working with the occupancy sensor: “The most common photosensor application included in hi-bay fixtures is a hold-off-type system incorporated within the occupancy sensor that prevents it from activating the fixture when adequate ambient light is available,” he says.

To understand the energy savings potential, a distributor need only look at its own warehouse facilities to see firsthand how often the lighting is operated in unoccupied spaces. But what about occupant acceptance? Are fixtures individually activating as workers move down a warehouse aisle likely to be accepted by the occupants, particularly if they are driving vehicles like forklifts?

Connolly says that in the end, seeing is believing, recommending that distributors take advantage of trial installation programs offered by manufacturers.

“Your customer is not looking to buy product, he is looking for a lighting system with better-quality lighting that uses less energy,” he says. “Find a contractor or service provider that you can build a relationship with to look for and address these opportunities. Offer your customers total turnkey solutions and you will add value beyond your competitors and discourage getting shopped out based on materials costs alone.”

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