Incandescent lamps are the most familiar source of light and are widely used
in residential and other low-annual-hours-use applications. The popularity of
the incandescent lamp is due to the simplicity with which it can be used and the
low price of both the lamp and the fixture. Also, the lamp requires no
special equipment, like a ballast, to modify the characteristics of its power supply.
Incandescents are often used in commercial and industrial applications where
the intended hours of use are low (less than 500 hours per year), where needed
for aesthetic purposes, or where initial cost is an overriding criterion.
The most common types are: the "A" or arbitrary bulb-shaped lamp; the "PS" or pear-shaped lamp; the "R" or reflector lamp; the "PAR" or sealed-beam lamp, and the tungsten-halogen lamp.
Although incandescents are the least efficient light sources, their advantages assure them a place in most homes and businesses for the foreseeable future. Therefore, we should at least use the wisely and recognize ways to save money using them. For instance, knowing that the efficiency of incandescent lamps increases as lamp wattage increases can allow you to save energy. This makes it possible to save on both energy and fixture costs whenever you can use one higher wattage lamp instead of two lower wattage lamps. For example, one 100-watt lamp produces more light, 1740 lumens, than two 60-watt lamps (860 lumens each) for a total of 1,720 lumens. Whenever you can substitute one 100 watt lamp for two 60s, you save 20 watts. Beware though, read the fixture ratings. Some are rated for 60 watt or lower lamps.
The specific type of incandescent lamp used and the kind of fixture involved
also make a difference. For example, a 75-watt ellipsoidal reflector lamp
delivers more light in a stack-baffled downlight than a 150-watt R lamp. This is
because much of the R lamp's light is trapped in the fixture and converted to
heat. The 75-watt ER lamp's shape and reflective interior focuses light down,
outside of the fixture, thereby producing more light on the surface.
Strengths:
Low initial cost
Excellent color rendition
Instant starting
Inexpensive dimming capability
Skin-flattering warm color
Small size, which allows it to be used in point fixtures, such as spot lamps
Wide variety of shapes, sizes, colors and wattages are available
Output unaffected by high or low ambient temperatures
Simple to operate and install
Requires no ballast
High brightness light source
Available in many colors
Variety of filament design possibilities offer optical control, accurate
distribution patterns and critical service operation
Weaknesses:
Relatively short useful life with poor over-voltage tolerance. At 10% over
voltage, life is reduced about 75%!
Very inefficient source of light. On average, less than 10% of the wattage
goes to produce light; the remainder becomes heat.
High heat component can create hidden energy costs due to increased cooling
needs.
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