Lighting options explained
05/01/2001
LIGHTING
by Robert Catone
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Linear fluorescent lamp
The linear fluorescent lamp advances in phosphor chemistry, lamp operating temperature and lamp diameter have dramatically improved fluorescent optical performance. New coatings called Tri-phosphors come in 2 grades that provide 17 percent to 28 percent higher lumen output than older coatings and almost perfect natural color. Smaller diameter T-5 and T-8 lamps block less light inside the fixture than old 1.5-inch T-12s. Efficiency rises 4 percent to 8 percent. The new T-5 lamp is 5/8-inch diameter and only 46-inches long. Its higher operating temperature provides more lumen output in sealed fixtures than 48-inch lamps. "High Output" (HO) lamps now have the same 20,000 hours of life as standard lamps. The chart below summarizes performance differences that can reduce the number of lamps and operating costs.
Linear fluorescent ballasts
Linear fluorescent ballasts are now operated by a microprocessor at 25,000-40,000 cycles instead of 60,000. The high frequency eliminates lamp flicker and extends lamp life. The latest designs are smaller and intelligent. Some can operate more than one wattage lamp at either 50 or 60 hertz and 120 or 277 volts. Internal losses are only 1 or 2 watts instead of 8 to 10 of old core-and-coil ballasts. Electronic ballasts can operate up to four lamps. Instant start versions operate lamps in parallel. If one fails, the others still operate. On the down side, electronic ballast component life is sensitive to heat. The cooler they run the longer they last.
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Ballast Factor measures the percentage of rated watts that is delivered to the lamp. Core-and-coil ballasts that were CBM certified had a ballast factor of 92 percent. They delivered 36.8 watts to a 40-watt lamp. The lamp emitted 92 percent of its rated lumens. Electronic ballasts from all manufacturers have ballast factors ranging from 60 percent to 115 percent. The one generally supplied is 90 percent. The potential for more light per lamp is obvious. Lamp life is unaffected by the higher power ballasts.
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Induction fluorescent lamp
Induction fluorescent lamp is a new system that uses microwave energy to excite the lamp. The lamp has a 100,000-hour life and is available from two manufacturers in sizes up to 165 watts. This system is about triple the cost of conventional fluorescents but may be suitable for high-maintenance-cost areas.
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Metal halide lamp
The metal halide lamp has crisp white color, is unaffected by temperatures and provides a large lumen package. It is usually the most economic choice above 14 feet. New technology using formed and ceramic arc tubes and upgraded ballasts have created Pulse Start Metal Halide. The system provides 40+ percent increase in maintained lamp lumens, uniform color, longer life and reduced re-strike time. Pulse Start lamp wattages now include 100, 150, 320, 350, 400 and 450 with more coming. The chart to the left illustrates the improved performance.
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Recessed fixtures
Recessed fixtures for non laminar-flow applications are available in cold rolled steel, stainless steel and aluminum. Stainless steel is an insulator and not as friendly to sensitive electronic ballast components as aluminum.
- Optics—new white finishes are semi-specular with a reflectivity over 90 percent. They increase fixture efficiency, which can reduce cost and energy significantly. Sealed louvers can eliminate computer screen glare and provide high visual comfort. The downward punch makes them more efficient in small rooms and at higher mounting heights than inverted lenses.
- Fit and finish—problems are solvable. It is now possible to model the fixture/grid interface with new 3-D CAD systems. Sealing a flange fixture to a sheet rock ceiling can be a problem. The 234 fixture's gasketed flange is held to the ceiling with only four brackets. The ceiling specifier should require that the ceiling be leveled with a laser to avoid caulking.
- Gasketing—requirements depend on the application and classification of the installation. Chip facilities generally are concerned with air quality and use inset doors with 6-point compression or hinged doors. Door gaskets are neoprene and the housing is generally sealed with silicone. Pharmaceutical facilities are most concerned with bacterial contamination. They may require washdown and normally use overlap doors with either 6 or 12 point compression. Gaskets are one piece or poured in place silicone or polyethylene. On walkable ceilings, top-access fixtures with sealed-bottom lenses are used.
Teardrop fixtures
Teardrop fixtures for laminar flow applications generally attach to the ceiling grid. Airflow disruption is minimized by the smaller fixtures designed around T-8 lamps. Screw slot grid in the ceiling increases the ease of installation.
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Integrated lighting systems
Integrated systems have been developed that put the lamps and ballasts inside the grid with either a flush or drop lens. They are most often used in rooms with 100 percent filtration and are installed by a specialized cleanroom contractor.
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Advances in technology when understood and properly applied can provide a low-cost and energy-efficient installation. Today's technology can provide 100 foot-candles at less than 1.75 watts a square foot.
Robert Catone is the general manger of Guth Lighting and vice president of JJI Lighting Group. He is a Certified Lighting Professional by the National Council of Qualifications for the Lighting Professions (NCQLP) and a member of the Illuminating Engineering Society Progress Committee.