UFC 3 -520-01
June 10, 2002
appropriate for applications where switching could be encouraged to save energy.
The fluorescent lamp should be about 60 percent of the original mercury vapor
Existing Exit Signs.
F-16.6.1 Incandescent exit signs should be retrofitted to either compact fluorescent or
LED, depending on the importance of a downlight component for exit pathway
F-16.6.2 Consider replacing exit signs with all new LED signs.
F-16.7.1 Spot relamping should be performed as necessary for appearance and safety.
F-16.7.2 Group rela mping should be the principal method of periodically replacing lights
in a given area. The group relamping frequency should be based on ensuring intended
lighting levels are maintained above minimum levels. Spot relamping is not
recommended in this regard because lighting levels will tend to eventually fall below
intended levels. The group relamping interval should consider the lamp mortality curve
(provided by the manufacturer for each type of lamp) so that spot relamping does not
become an excessive maintenance burden. Any group relamping activity should
include fixture cleaning to obtain optimal results.
HARMONIC DISTORTION CAUSED BY LIGHTING SYSTEMS .
Electronic ballasts increase lamp efficacy by converting 60 Hertz power into
high-frequency (20 kilo-Hertz to 40 kilo-Hertz alternating current). This conversion
process adds to the harmonic distortion on the electrical system. In extreme conditions,
the harmonic distortion can overload neutral conductors and affect electronic
equipment. In almost all cases, the contribution of lighting system -induced to the
electrical system harmonic distortion will not be significant. Table F -5 provides typical
total harmonic distortion (THD) generated by various electrical and electronic
equipment. Notice that high efficiency magnetic ballasts can generate as much
harmonic distortion as electronic ballasts. Newer electronic ballasts tend to produce
even lower levels of harmonic distortion. Notice also that certain electronic ballast
compact fluoresce nts tend to cause the greatest harmonic distortion.