EGEE 102H Exam 2
Terms in this set (8)
Factors affecting the number of lamps required
1) Fixture efficiency: certain fixtures reflect or absorb more light than the others.
2) Lamp lumen output: the efficiency of the bulb increases with the wattage.
3) The reflectance of surrounding surfaces: bright colors or reflective surfaces painted with glossy texture finishes will appear brighter than the surface with flat finish paint.
4) The effects of light losses from lamp lumen depreciation and dirt accumulation: as the lamps age or when the dirt accumulates on the bulb surface, lumen output decreases. Newer light bulbs produce more light than the older bulbs for the same wattage.
5) Room size and shape
6) Ability of natural light (daylight)
Four basic types of lighting
3) High-intensity discharge
4) Low-pressure sodium
* Filament gets heated up and radiates
* Filament temperature is very high, over 2,000 or 3,600 degrees.
* Incandescence: about 5 percent of the electrical energy converts into visible light and the rest is emitted as heat or infrared radiation
* Halogen bulbs: 10-20 percent more efficient than an ordinary incandescent bulb.
- 2 to 3 times as long a lifetime as ordinary bulbs.
* 2 to 4 times more efficient as incandescent lamps at producing light at the wavelengths that are useful to humans.
* Run cooler.
* Last a lot longer, almost 10 times more.
* Compact fluorescent lamps have 10 to 20 times longer life than standard incandescent.
* More costly than incandescent.
* Cost more, but economical in the long run (one of the best energy efficiency investments available)
High-intensity discharge (HID)
* HID lamps were originally developed for outdoor and industrial applications
* Advantages: long life, small size, high lumen output per watt
* Disadvantages: require warm up time, restrike time
* Metal halide: good for sports arenas and stadiums, large auditoriums and convention halls.
* High pressure sodium lamp
* Mercury vapor lamps
High pressure sodium lamp (part of HID)
* Better than metal halide for outdoor applications when good color rendering is not a priority
* Efficacy is very high
* Produces golden color due to sodium.
* Efficacy of low-wattage "white" HPS lamps is lower than that of metal halide lamps
* Most energy efficient, out of incandescent, HID, and fluorescent
Low pressure sodium lamp
* Highest efficacy of all commercially available lighting sources
* Yellow light
* Operates like a fluorescent lamp and requires ballast.
* Large, meaning light distribution from fixtures is less controllable
* Brief warm-up period before reaching full brightness
* CRI is 0- color rendition is not important but efficiency is.
* Outdoor, roadway, parking lot, pathway lighting.
* Preferred around astronomical observatories because the yellow light can be filtered out of the random light surrounding the telescope
Disadvantages to CFLs
* Physically larger than the incandescent bulbs and may not fit the lamp
* Light is generally cooler, or less yellow, than incandescent. Unpleasant contrast with ordinary lamps and fixtures.
* Some types (iron ballasts) produce annoying flickers
* Ordinary dimmers cannot be used with compact fluorescents
* Operation at cold temperatures may result in reduced light output
* May be an audible buzz from the ballast
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