Quantcast Section III- Light Distribution

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TM 5-684/NAVFAC MO-200/AFJMAN 32-1082
0.5 milliampere, it should be returned to the manu-
block and remove the panel. Contacts should be
inspected and replaced if badly pitted. On contacts,
facturer for rehabilitation, or replaced with a photo-
other than silver-plated ones, a coating of nonoxide
conductive cell. The relay for a phototronic cell is
very delicate because of the small amount of energy
grease is desirable. When grease cups are provided
needed to operate it. Misoperation is most often the
for the front and rear motor bearings, the grease
result of sticking contacts and damaged bearings.
cups should be given a half turn every 3 months.
Sticking contacts should be carefully cleaned with
The manufacturer's recommended grease should be
crocus cloth. Damaged bearings are usually caused
used for refilling. The clock mechanism should be
by severe continuous vibration or knocks. Any
overhauled every 5 years by the manufacturer or a
maintenance on the relay panel, other than the
competent watchmaker.
b. Contactors. Contactors are described under
cleaning of contacts mentioned above, should be
done by the manufacturer. Careful handling is es-
chapter 11, section II.
c. Photo cells. Any dust or dirt on the windows of
(2) Phototube photocell. A periodic checkup
photo controls of any type will prevent proper opera-
should be made every 6 months. The windows
tion. These windows must be kept clean.
(1) Self-generating phototronic photo cell. The
should be cleaned and all tubes replaced. Replaced
tubes should be checked by a competent tester and
self-generating phototronic cell has a normal clear
discarded if poor. Any extensive maintenance work
day output of 1.5 to 6 milliamperes. It can operate
should be considered justification for replacing with
the relay on 0.5 milliampere, so replacing the light
collector is not necessary until its output tests below
a solid-state type.
(3) Solid-stat e photocell. Failure of this type is
0.5 milliampere. Any testing should be made on a
denoted by lights being on during daylight. If clean-
cloudless day using a milliammeter with a range of
ing the window does not correct the malfunction,
0 to 10 milliamperes. The check can be made most
the unit should be replaced. The high repair labor
conveniently at the terminals on the relay box.
cost usually exceeds the replacement cost.
When the output of the light collector tests less than
6-9. Light distribution standards.
b. Type II. The distribution of (c) produces more
spread than does type I. It is intended for roadways
Industry standards regulate outdoor lighting de-
with a width of about 1.6 times the lamp mounting
sign. Luminaires are designed to provide light dis-
height, with the lamp located near one side. The
tributions to meet the design standards by focusing
variation of (d) is suitable for intersections of two
the light into the patterns, beam spreads, or cutoffs
such roadways, with the lamp not near the center of
as applicable.
the intersection.
6-10. Roadway lighting.
c. Type III. The distribution of (e) is intended for
IESNA's Lighting Handbook lists five basic distri-
luminaires located near the side of the roadway
butions. Figure 6-l and the distribution discussions
with a width of not over 2.7 times the mounting
following have been provided to simplify IESNA
definitions. While many luminaires can be adjusted
d. Type IV. The distribution of (f) is intended for
to produce more than one pattern, no luminaire is
side-of-road mounting on a roadway with a width up
suitable for all patterns. Care must be used, espe-
to 3.7 times the mounting height.
cially in repair and replacement, to install the
e. Type V. The distribution of (g) is circular and is
proper luminaire for the designed pattern, as speci-
suitable for areas and wide roadway intersections.
fied in manufacturer's literature. Even when the
Types III and IV can be staggered on opposite sides
proper luminaire is installed, care must be used to
of the roadway for better uniformity in lighting
ensure all adjustments have been properly made to
level, or for use on wider roadways.
produce the desired results.
a. Type I. The distribution of (a) is intended for
6-11. Floodlighting.
narrow roadways with a width about equal to lamp
Floodlighting is used for recreational lighting and
mounting height. The lamp should be near the cen-
ter of the street. The variation of (b) is suitable for
for area lighting. Floodlighting is defined by the
NEMA field angle as indicated in table 6-l with
intersections of two such roadways with the lamp at
projection distance given in feet (ft) and meters (m).
the approximate center.


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