fluorescent lamps, but offer a means of
easily increasing the efficiency of an
incandescent luminaire.Light output
During the first one hundred hours of burning
a new fluorescent lamp, the initial lumen
output drops by about 5 percent; lumen
reduction thereafter is less rapid. Conse-
quently, the published “initial lumens” for
fluorescent lamps is the value obtained after
the first hundred hours of burning.
The depreciation in light output during
the life of the lamp is approximately 15 per-
cent of the initial lumens. This is the result of
the gradual deterioration of the phosphor
powders and the evaporation of electron-
emissive material from the cathodes, which
causes blackening of the glass bulb adjacent
to the cathodes.
The end of life is reached when the
emission material on either cathode is
depleted. Failed preheat lamps flash on and
off or extinguish; instant-start and rapid-start
lamps extinguish, flicker, or operate at
reduced luminance.
Lamp life
Lamp life varies with the different kinds of
fluorescent lamps. Rated average life of fluo-
rescent lamps is based on the average life of
a large representative group of lamps tested
in a laboratory under controlled conditions; it
is expressed in “burning hours.” Preheat
lamps have rated average lives of 7,500 to
9,000 hrs, slimline lamps 7,500 to 12,000
hrs, rapid-start lamps 14,000 to 24,000
hrs, high-output lamps 9,000 to 12,000
hrs, and very-high-output lamps 10,000 to
12,000 hrs.
The starting of all fluorescent lamps is
affected by the ambient temperature. Low
temperatures require higher voltages for reli-
able starting. The majority of ballasts provide
voltages that start standard lamps down to
50°F. Ballasts are available for certain kinds
of lamps that can start lamps down to 0°F
and down to –20°F.
Because each start further depletes the
tungsten cathodes, the average life of fluo-
rescent lamps is affected by the number of
lamp starts. Frequent starting shortens life;
life is lengthened as the number of burning
hours per start is increased. Published lamp-
life ratings are based on an arbitrarily
assigned three hours of burning per start.
The life of cold-cathode lamps is unaffected
by the number of starts.EPACT
The U.S. Energy Policy Act of 1992 (EPACT)
established minimum efficacy standards for
certain kinds of fluorescent lamps. The effi-
cacy standards are a combination of mini-
mum average lamp efficacy, measured in
lumens per watt, and minimum color render-
ing index (CRI). No full-wattage F40, F40/U,
F96, or F96/HO lamps can be manufactured
or imported unless the lamp has a CRI of 69
or higher and meets the minimum-efficacy
requirement.
Full-wattage CW, D, W, WW, and WWX
lamps are now unavailable; energy-saving D
and WWX lamps are unavailable. CW, D, LW,
W, WW, and WWX F96T12 and F96T12/HO
lamps have been prohibited from manufac-
ture or sale in the United States since 30
April 1994. CW, D, LW, W, WW, and WWX
F40T12 and F40T12/U lamps have been
prohibited from manufacture or sale in the
United States since 31 October 1995. See
table 3 in the Appendix.
Lamps with a CRI of 82 or higher are
exempt from these efficacy standards. In
addition, aperture, cold-temperature, col-
ored, impact-resistant, plant growth, reflec-
tor, and ultraviolet lamps are exempt from
the standards.
Until 1992, most fluorescent lamps
used for architectural lighting in the UnitedDISCHARGE LAMPS