Building Operating Management

Lighting



Keeping up with lighting technology


By Lindsay Audin   Lighting

There have been a lot of changes in lighting technology that may make reconsidering retrofitting systems that are only 5-years old worthwhile. Where electric rates are high, even systems that seemed high-tech in 1998 may be worth upgrading. For new construction or major renovations, taking advantage of these new technologies can make the difference between an adequate design and an effective one.

Lighting innovations continue developing, with each advance offering another opportunity to reduce electric bills, improve quality and cut maintenance costs. In some high-energy-cost areas, some facility executives are already deploying T5 lamps, using metal-halide track lights and integrating sophisticated lighting controls into building-management systems (BMS). Elsewhere, some are just starting to replace T12s with T8s and electronic ballasts.

If a facility already has 32-watt T8s, standard electronic ballasts, some metal-halide downlights, and a system that automatically shuts off each floor’s lights, how could it be improved?

Fluorescent Lighting Innovations

In common areas, such as hallways and lobbies, 32-watt T8 lamps could be replaced as part of a routine relamping with only 28- or 30-watt T8s and provide the same illumination. If a T8 upgrade done years ago used instant-start ballasts, a ballast change will not be needed. This relamping will save 10 to 12 percent on the lighting bill. If ballasts specifically designed to work with the new lamps are later installed, savings of 18 percent are possible.

In spaces that need a slight lighting boost, replacing existing ballasts with units having a higher ballast factor (BF) that overdrive T8 lamps could provide up to 35 percent more light from the same fixture without compromising lamp life.

Lamp burnouts could be reduced by switching to programmed-start ballasts that add another 10,000 hours to the standard T8 lifetime of 20,000 hours at the usual 3 hours per start. Where changing ballasts isn’t appropriate, long-life T8 lamps could be installed, increasing lamp life by 20 percent. In some high-end locations, higher grade T8s with better color and lumen retention may now be found.

In Class A offices and reception areas, glary T8 troffers could be replaced with cove-mounted indirect T5 fixtures. Because of their size, T5 lamps also permit use of smaller fixtures. By bouncing light off ceilings and upper walls, T5s provide glare-free light that also makes rooms feel more spacious. In its high-output (HO) version, a T5 emits nearly twice the light of a T8 lamp of the same length.

Compact Fluorescents Grow Up

In atriums, high-bay metal-halide (MH) fixtures, with their varying color and brightness, could be replaced one-for-one with like-sized units each containing four to eight compact fluorescent lamps (CFL). Unlike the MH fixtures, CFLs come on instantly, even after a power failure, and maintain high color quality throughout their life. They can be dimmed down by 90 percent or more, depending on the ballast, during off hours or when daylight enters the space. The CFLs are 42-watt lamps that emit more lumens in their 7-inch long, six-tube configuration than a 48-inch T8 lamp. CFLs are now available up to 70 watts. Many firms now offer multi-CFL fixtures for high-bay applications, such as atriums, gyms and exhibit halls.

Hid Looking Better

In a warehouse lit by high-pressure sodium (HPS) lamps, it’s possible to use metal-halide lamps that offer better color without replacing either fixtures or ballasts. In other locations, MH fixtures now equipped with new ballasts and MH lamps that start and restart faster than the previous equipment provide better lumen maintenance, cut wattage by 15 to 25 percent and don’t sacrifice brightness.

On the ground floor of a retail store, hot incandescent track lights could be replaced with electronic ballasts and mini-MH fixtures, equipped with high color rendering ceramic metal-halide (CMH) lamps. CMH lamps are about the same size and offer the same tight focus as incandescent lamps that use four times their wattage and burn out eight times more often. While nothing presently equals the crisp color of the best halogen lamps, CMH lamps produce better quality output than some standard incandescent and most fluorescent sources. Typical CMH lamps have a color-rendering index (CRI) of 80 to 92 and color temperatures of 3000 to 3600 K.

The changeout is easy: By using a lightweight adapter that slips into most existing tracks, CMH fixtures require no rewiring.

Control Gets Easier All The Time

Light levels can drop using dimmable ballasts controlled by a Digital Addressable Lighting Interface (DALI) system. DALI, connected by a pair of thin wires to each fixture, sends out signals telling specific ballasts how much light to emit, and when. During the day, it may slowly dim the lights by 30 percent, which tests have shown will rarely be noticed, to cut peak demand when needed.

While the DALI system is probably the most flexible option for controlling lighting, some existing lighting systems are becoming BACNet® compatible, simplifying integration with that HVAC control system.

When an area cannot be accessed to install the DALI wiring, a different approach should be taken. Using dimmable ballasts that listen for control signals coming through existing power wiring, light levels are controlled by a power-line-carrier (PLC) system.

Wall Switches Get Smarter

To add more versatility, facility executives could turn to occupancy sensors that sense body heat and sound, and emit ultrasonic signals to detect motion. Such devices aren’t fooled by reflections, oscillating fans or radiators. In closets, economical electronic timer switches could replace standard wall switches to shut off lights after a defined time interval.

In open areas divided by cubicles, wall-mounted sensors would not be appropriate, so standard switches could be replaced by automatic switches that can be controlled by PLC signals, which flicker the lights briefly to let occupants know that lighting will go off in five minutes. To override the sweep, occupants need only to push the switch. That keeps the lights on until the next sweep signal is sent out.

Controls Built Into Fixtures

New fixtures can satisfy a range of needs of tenants. With some, two dimmable ballasts in pendant-mounted direct-indirect fixtures, uplight and downlight may be separately controlled. Using PC-based software, each occupant can adjust the level of downlighting while the BMS handles uplighting as part of scheduling and demand-reduction strategies. An occupancy sensor built into each fixture watches occupants below and, during absences, gradually reduces (but does not shut off) that fixture’s downlighting. A daylighting sensor in each fixture reduces uplight when natural light from windows makes up the difference.

In stairwells, new fixtures equipped with a built-in occupancy sensors and bi-level ballasts that drop the light and power level by 50 percent or more, if allowable, could be used. Safety and security are maintained while a 24-hour power draw is cut in half. The instant anyone enters the stairwell, nearby fixtures would come up to full output. Studies show that stairwells in office buildings are occupied only about 10 percent of the time, while high-rise apartment stairwells see occupancy only about 30 percent, making this option a major energy saver.

All That Glitters Not Always Glorious

As with any new lighting technology, always remember to test before investing. Before adopting a broad change, try it out in a controlled test location. The installation can be tweaked to fit particular needs without disturbing occupants. Find reviews on many new lighting technologies at The Lighting Research Center.

Some new technologies are subtly different from their predecessors. When T5s, for example, are run on the same type of electronic ballast as T8s, such as programmed-start, T5s don’t last as long as T8s. They also take longer to warm up to full brightness. That’s important when controlling T5s with occupancy sensors. When a T5 cools to room temperature, say 75 degrees, it will take more than three minutes to come back up to full brightness when next lit. In areas equipped with night setback temperature controls, expect spaces to be a bit dim for up to seven minutes while the T5s warm up.

And don’t be fooled by claims that T5s are much more energy efficient than T8s. Any actual difference may be affected by the fixture housing style — open cove or enclosed troffer — and the way each lamp/ballast combination is rated. T5 lamps provide greater output at temperatures typically seen in enclosed fixtures, such as 95 degrees, whereas T8 output is maximized at 78 degrees. When a T8 exceeds that temperature, its light output drops. T5 efficacy in lumens per watt is rated using electronic ballasts that boost light output of any fluorescent lamp by about 12 percent more than magnetic ballasts. T8 lamps, however, are typically rated using magnetic ballasts. In the end, the difference in efficiency may be marginal.

Lindsay Audin is a contributing editor and president of EnergyWiz, an energy consulting firm based in New York.




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  posted on 8/1/2003   Article Use Policy

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