produced by the lamp-ballast combination;
the input watts are an indication of the
power consumed.
For example, a ballast with a ballast
factor of 0.88 using 60 W of input power has
a ballast efficacy factor of 1.47 (0.88 × 100
÷ 60 = 1.47). Another ballast using the
same input power with a ballast factor of
0.82 has a ballast efficacy of 1.37 (0.82 ×
100 ÷ 60 = 1.37). The first ballast therefore
offers greater efficacy because it has a higher
ballast efficacy factor (1.47 versus 1.37).
An electromagnetic ballast operating
from an alternating current source produces
a sound called “hum.” The degree of hum
varies depending on the kind of ballast. To
aid in the selection of ballasts, manufactur-
ers give their ballasts a sound rating that
ranges fromA(the quietest, at 20 to 24
decibels) toF(the loudest, at 49 decibels
and above).
Electronic Ballasts
Theelectronicballast, based on an entirely
different technology from the electromag-
netic ballast, starts and regulates lamps with
electronic components rather than the tradi-
tional core-and-coil assembly. The lighting
systems they operate convert power to light
more efficiently than systems run by electro-
magnetic ballasts.
Rather than produce more light output,
electronic ballasts are usually designed to
produce the same quantity of light as elec-
tromagnetic ballasts, but they use less
power and thereby reduce energy costs.
HID electronic ballasts provide better
output regulation (current and power), inde-
pendent of input voltage variations or lamp
wattage variations. This keeps color output
(CCT and CRI) consistent and lumen output
more uniform. Compared to electromagnetic
systems, HID electronic ballasts provide
improved performance in starting, normal,
and restrike operations.
The humming sound associated with
electromagnetic ballasts results from the
vibration of the steel laminations in the core
and coil. Because electronic ballasts do not
have the laminated core and coil, they are
75 percent quieter than comparable A-rated
electromagnetic ballasts.
Electronic ballasts operate fluorescent
lamps at higher frequencies than electro-
magnetic ones, with the advantages that
flicker is eliminated and lamp efficacy is
increased. Both of these advantages occur
because the lamp phosphors are under
more constant excitation with high-fre-
quency operation.
Electronic ballasts are also smaller and
lighter in weight than electromagnetic ones,
typically weighing less than half as much
because the electronic components are
lighter than the metal components of the
core-and-coil assembly. Because electronic
ballasts consume fewer watts than electro-
magnetic ballasts, they also produce less
heat. This cooler operation yields significant
savings in air-conditioning costs.Air-Conditioning
The air-conditioning load caused by electric
lighting derives from the total lighting
system, including lamps and ballasts. Each
kilowatt(kW) of electric power used by the
lighting system adds 3,412 British thermal
units (BTUs) to the air-conditioning load.
One ton of air-conditioning = 12,000
BTU. Therefore, every 3.5 kW of lighting
requires one-ton of air conditioning.
12,000
3,452=3.5 kWFluorescent Dimming Ballasts
Electronic fluorescentdimmingballasts will
dim T5, T5 high-output, T8, and T12 fluores-
cent lamps to 1 percent of measured light
output (10 percent of perceived light). (LightAUXILIARY EQUIPMENT