LightingAbout
Lighting
Lighting accounts for 15% of power
consumption of the typical American household.
The two most
common types of lighting are Incandescent and Fluorescent.
Incandescent lights are descendents of Thomas Edison's original light
bulb. They are used in table and floor lamps, downlighting, and
outdoor fixtures. They come in a variety of wattages for varying
levels of light intensity.
When energized, incandescent bulbs
produce a yellow colored light. Colors on objects seen under an
incandescent light are considered to be "true".
Incandescent performance
characteristics are as follows:
Wattage
Lumens* Life
(hours)
40
|
445
|
1500
|
60
|
870
|
1000
|
75
|
1180
|
750
|
100
|
1710
|
750
|
* Lumen, or luminous flux, is the
unit of measure for light intensity
Fluorescent lamps come in the
familiar straight and circular tube form, and are now also available
as compact bulbs. Compared to incandescents, fluorescent lights have
higher energy efficiency and emit light that is described as
"bluer", "cooler", and "white".
Fluorescent fixtures with
electromagnetic ballasts have a visual flicker, are slow to start up,
and develop a humming noise over time. With the introduction of
electronic ballasts, these problems have gone away, increasing the
marketplace acceptance of fluorescent lighting.
Fluorescent performance
characteristics are as follows:
Wattage
Lumens*
Life (years)
40
|
3000
|
13
|
34
|
2700
|
13
|
32
|
2950
|
13
|
An incandescent light bulb consists
of a tungsten filament enclosed in an evacuated space. The filament
essentially acts as a resistor for the electrical current applied to
it. As the filament heats up, it glows, thus providing useful light.
The frosting on the inside to bulb serves to diffuse the light
radiating from the filament.
A fluorescent tube or
"lamp" consists of a long thin glass tube filled with low
pressure mercury vapor. As an electrical charge is applied to the
tube, the conducting mercury vapor emits UV waves. As these waves pass
through the phospor coating on the inside of the tube, they convert to
visible light.
To provide the proper kind of
electrical charge to a fluorescent tube, a ballast is required. In
general, the higher the output frequency of the ballast, the higher
the efficiency of the tube in operation. For this reason, high
frequency (25-35kHz) electronic ballasts, outperform the low frequency
(<15kHz) electromagnetic ballasts.
If you touch an incandescent bulb
when it is on, you will burn your fingertip. If the do the same with a
fluorescent tube, it will feel warm, but not burning hot. Relative
coolness to the touch indicates the higher energy efficiency of the
fluorescent. For the same lighting level, fluorescent will use 70-75%
less electrical energy.
Lighting color is measured on two
different scales: temperature and color rendering index (CRI).
Temperature measures in degrees Kelvin. Lower temperature light
(2000-3000K) gives objects a warm red color, while higher temperature
(4000-7000K) light projects a cool blue-green hue. The median
temperature of 3500K compares to the noonday sun, which is the
benchmark of color "trueness".
The Color Rendering Index (CRI)
measures color contrast. Its scale runs from 0-100. Incandescent and
Halogen bulbs generally have a CRI close to 100. The closer to 100 the
CRI measures, the "truer" the colors will appear.
Consider where you want to see true
colors at home. Your clothes closet, living areas, kitchen, and baths
are likely candidates. Do you want the clothes that you put on this
morning to look different when you go outside?
Seeing color trueness may not be as
important in the garage, hallways, basement, or your home office.
However, today's technology allows you to have fluorescent light that
produces a truer light. Color-corrected fluorescents cost slightly
more, but provide almost the same color light as incandescents.
One disadvantage commonly associated
with fluorescent lighting is the humming noise that older fixtures
emit. Humming occurs only with magnetic ballasts. Newer electronic
ballasts operating at much higher frequencies, do not hum or do so
minimally.
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Copyright © 2003 HEM Technologies, LLC. All rights reserved.
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