and tungsten-halogen lamps undergo con-
siderable shifts toward the orange-red end of
the spectrum when they are dimmed.
Although this increases the warm appear-
ance of the lamps at lower light intensities, it
is a positive result because people prefer
warmer colors of light at lower intensities
(figure 11.9).
The efficiency of an incandescent lamp
is reduced when the source is operated at
less than its designed voltage because the
temperature of the filament is reduced. Even
though the lamps are less efficient at pro-
ducing light, much energy is still being saved
(figure 11.10).
In some applications, normal operation
of dimmers causes lamp filaments to “buzz.”
Lower-wattage lamps, physically smaller
lamps, rough service (RS) lamps, low-noise
stage lamps, and lamp debuzzing coils help
to decrease this noise.
The lampdebuzzing coilis a separate
component. It, too, will hum during opera-
tion, so it is remotely located in an area
where this noise will be acceptable (for
example, a closet or adjacent room).Low-voltage lamps
Dimmers for incandescent low-voltage
luminaires are installed on the 120 V side of
the low-voltage transformer. Two kinds of
transformers are manufactured for low-volt-
age lighting: magnetic (core-and-coil) and
electronic (solid-state).
Before selecting a dimmer control, it is
necessary to determine which kind of trans-INTERIOR LIGHTING FOR DESIGNERS
Figure 11.9Dimming incandescent and tungsten-halogen lamps moves light toward the warmer end of the color spectrum.