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 TM 5-683/NAVFAC MO-116/AFJMAN 32-1083
CHAPTER 9
ILLUMINATION
ments. Older models with simple (single winding)
9-1. Lighting maintenance.
reactance ballasts are an exception. The NEC Ar-
Each lighting installation is designed to produce a
ticle 410-18(a) also requires that fluorescent fix-
specific level of illumination adequate for those
tures as well as all other lighting fixtures and
working in the area. Adequate illumination should
equipment with exposed conductive parts be
be maintained to reduce eyestrain, improve morale,
grounded. Failure to properly ground the ballast
increase safety, improve housekeeping, decrease fa-
and fixture combination could result in shock haz-
tigue, reduce headaches and increase production,
ard. In addition to a shock hazard, failure to prop-
all of which are directly reflected in lower operating
erly ground a fixture may result in frequent tube
cost. The maintenance of lighting systems is aimed
failures and trouble with starting for certain de-
at preserving the light producing capability at the
signs. For relamping or lighting retrofit it is impor-
original design level. Its necessity cannot be over-
tant to assure existing ballast is in compliance with
emphasized. To prevent progressive deterioration of
the new lamp. For example, when replacing a T-12
the system, prompt repair of any deficiency is essen-
with a T-8 lamp the new ballast for the T-8 should
tial. Since dirt accumulating and lamp aging are the
be installed since the existing T-12 ballast is incom-
two major factors which reduce the light output, it
patible although the lamp bases are similar.
is necessary that lamps, fixtures and reflective ar-
9-3. Incandescent lighting.
eas be kept clean; defective lamps be replaced; and
In an incandescent lamp, light is generated by heat-
the voltage be held stable.
ing the filament to incandescence. The hotter the
9-2. Fluorescent lighting.
filament, the more efficient it is in converting elec-
tricity to light. However, when the filament oper-
There are three principal types of fluorescent fix-
ates hotter, its life is shortened. Therefore the de-
tures; preheat, instant-start and rapid-start. All
sign of each lamp is a balance between efficiency
have practically the same physical dimensions but
and life. Incandescent lighting fixtures are designed
different internal construction. A preheat fixture
for a particular lamp size and type. However, it is
has a ballast and starter which supplies nominal
possible to use much higher wattage lamps in a
voltage to the lamp (fig 9-l). These are older style
fixture than the fixture or the circuit can ad-
fixtures which cause the fluorescent tube to flicker
equately handle. The excessive heat of higher watt-
before it lights. An instant-start fixture has a bal-
age lamps can damage the sockets, increase failure
last which supplies a high voltage to the fluorescent
rates and overload the circuits. Personnel are cau-
tube to light it instantly. A rapid-start fixture has a
tioned to use only the lamp size (in watts) recom-
ballast which requires a starting aid voltage be-
mended for the fixture or smaller rather than a
tween the full length of the lamp and the grounded
higher wattage lamp that may physically fit. Incan-
metal surface of the fluorescent fixture. The type of
descent lamps come in a variety of voltage ratings.
circuit in which a particular lamp must be used is
For most applications, the lamp voltage rating near-
etched on the end of the lamp. For most applica-
est the available line voltage should be selected.
tions, the 4-foot rapid-start lamp is the preferred
Under this condition, the lamp will produce its
lamp. Energy efficient lamps and electronic ballasts
rated value of life, watts and light output. Energy
are also available. They can replace standard fluo-
efficient replacements are available for standard in-
rescent lamps and save electricity by providing full-
candescent lamps. They provide better lamp effi-
light output at reduced wattage and operating tem-
ciency with no loss in lamp life. Many incandescent
peratures. Electronic ballasts can save up to 25
lamps are available with life ratings in excess of
percent of the energy. The advantages of the elec-
ordinary general service lamps. Some have ratings
tronic ballast besides energy saving, are lighter
of 5,000 hours or more and some even are guaran-
weight, less humming noise, dimmable and capable
teed to burn for five years. Use of these lamps may
of operating up to four lamps at a time. The Na-
be practical at locations where access is limited in-
tional Electrical Code Article 410-73 requires that
cluding high ceiling auditoriums, exit lights, stair-
all indoor fluorescent fixtures (except those with
wells, and marker lights on towers or fire alarm
simple reactance ballasts) incorporate Class p bal-
boxes. Use of an ordinary general service lamp
lasts with integral thermal protection. This require-
whose voltage rating is higher than the circuit volt-
ment applies to all new installations and replace-
9-1
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