22 August 2006
flicker effect may be noticeable in certain applications and can be effectively eliminated
with the use of high frequency electronic ballasts7. If electronic ballasts are not used,
the phases can be rotated to minimize flicker.
Interference. Electronic ballasts have the potential to cause Electromagnetic
high frequency electronic equipment. This can be a significant issue when installed
near electronic medical equipment. To prevent such interference, specify magnetic
ballasts in those areas. Another more energy efficient option that will also avoid such
these ballasts operate at low frequencies and will not interfere with sensitive equipment.
These ballasts should be specified with <20% Total Harmonic Distortion (THD).
Effects of Temperature. Ambient air temperature affects the performance and
output of fluorescent lamps. In exterior, low temperature applications (less than ten
degrees C) provide ballasts capable of low temperature lamp starts. Light output will be
reduced until lamp warms up to operating temperature. Mercury amalgams added to
fluorescent lamps improve the lamp performance and provide for operation over a wide
temperature range. These lamps typically take slightly longer to reach normal operating
temperature and full light output.
Life. The operating temperature of ballasts directly affects the life. The
luminaire housing or ballast enclosure should provide for adequate dissipation of heat.
When ballasts operate at excessive temperatures, the insulation degrades, resulting in
a shortened ballast life.
Control system design. When controls are used wisely, the benefits of
occupant satisfaction and energy savings can lead to long lasting economic benefits.
When designing controls, evaluate areas as to whether they are task or non-task
dominant areas. Task dominant area examples include offices, conference rooms,
classrooms and maintenance areas. Non-task dominant area examples include
transition areas such as corridors, lobbies, atriums or support areas such as cafeterias,
restrooms, and storage areas. Even the best-designed control strategy does not work if
people feel "controlled" and over-ride the controls.8
5-5.1.1 Task dominant areas. Daylight dimming provides the highest level of
satisfaction since the lighting smoothly responds to daylight availability versus an abrupt
on/off. Ideally, manual dimming with an upper daylight limit provides the greatest
flexibility and highest acceptance since people have control over their areas. In
addition, occupancy sensors allow the lighting to turn off if no one is in the area.
"Light Sources", Lighting Handbook Reference and Application, Chapter 6, Ninth Edition (New York: The
Illuminating Engineering Society of North America, 2000), p. 6-50.
"Lighting Values", Light Right Consortium, 2001 - 2003 <http://www.lightright.org>