Luminaires
Almost all lamps require a method to curtail glare; in addition, many need a
method to modify distribution.
Aluminaireprovides physical support, elec-
trical connection, and light control for an
electric lamp. Ideally, the luminaire directs
light to where it is needed while shielding the
lamp from the eyes at normal angles of view.
Luminaires are composed of several
parts that provide these different functions:
the housing, the light-controlling element,
and the glare-controlling element. Depending
on the design requirements and optical con-
trol desired, some of these functions may be
combined.
Housings
The electrical connection and physical sup-
port for the light source are provided by the
luminairehousing. Often its electrical auxiliary
equipment, when required, is also incorpo-
rated. Housings are divided into five catego-
ries based on how they are supported:
recessed, semi-recessed, surface-mounted,
pendant-mounted, and track-mounted.
Recessedhousings are mounted above
the finished ceiling, are entirely hidden from
view, and have anaperture(opening) at the
ceiling plane to allow light to pass through.
Some recessed housings are designed to be
mounted into the wall, the floor, or the ground.
The electrical connection between the
building wiring and the luminaire is made at
thejunction box, which is often attached to
the housing (figure 12.1). UL standards
require that the connection (“splices”) of
luminaire wires to branch circuit wires be
accessible for field inspection after the light-
ing fixture is installed. This access is usually
accomplished through the aperture of the
luminaire.
Semi-recessed housings are mounted
partially above the ceiling with the remainder
visible from below (figure 12.2). Sometimes
the semi-recessed housing is mounted par-
tially in the wall with the remainder project-
ing, and in rare cases it is mounted partially
below the floor with the remainder visible
from above.
Surface-mountedhousings are mounted
to the surface of a ceiling, a wall, or, in rare
cases, a floor. If the ceiling or wall construc-
tion permits, the junction box is recessed into
the mounting surface, giving a cleaner
appearance (figure 12.3); otherwise, the
junction box is mounted against the surface
of the ceiling or wall (figure 12.4).
In both cases, the housing serves to par-
tially or entirely conceal the junction box.