counterpoise. The light fixtures, equipment, and
buildings are connected to the grounding circuit. If
necessary, grounding to the counterpoise may be
permitted.
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3.14.1
Counterpoise Installation
Counterpoise wire shall be placed for entire length of circuits supplying
helipad lighting. Wire shall be provided in one piece, except where
distance exceeds the length usually supplied. Counterpoise shall be
installed on top of the envelope of concrete-encased duct and approximately
150 mm 6 inches above direct burial cables and duct lines. Where trenches
or duct lines intersect, counterpoise wires shall be electrically
interconnected wires by exothermic welding or brazing. Counterpoise shall
be connected to earth ground at every [600 m] [_____] m [2,000] [_____] feet
of cable run, at lighting vault, and at feeder connection to light circuit
by means of ground rods as specified. The counterpoise shall be installed
in a separate duct under roads, railroads, and paved areas above the
highest duct containing electrical or communications circuits.
3.14.2
Fixture Grounding
Each fixture or group of adjacent fixtures shall be grounded by a grounding
circuit separate from the counterpoise system unless required otherwise or
by driven ground rods if permitted. Fixtures, steel light bases or
grounding bushings on steel conduits shall be connected to an independent
ground rod by a No. 6 AWG base-stranded copper wire. Semiflush fixtures
for direct mounting in pavement need not be grounded. Copper wire shall be
connected to ground rods by exothermic weld or brazing.
3.15
MARKING AND LIGHTING OF AIRWAY OBSTRUCTIONS
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NOTE: If Section 09900, PAINTING, GENERAL is
included, painting requirements should be
transferred to it. Local conditions may necessitate
modification to the following paragraph. Refer to
FAA AC 70/7460-1 for further marking of obstructions.
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Towers, poles, smokestacks, buildings of certain shapes and sizes, and
other obstructions shall be marked and lighted in accordance with FAA AC
70/7460-1 and as indicated.
3.15.1
Painting of Airway Obstructions
Patterns and colors to mark obstructions shall conform to FAA AC 70/7460-1
and be as indicated.
3.15.2
Obstruction Marker Lights
Obstruction marker lights shall be installed on radio towers, elevated
water tanks, smokestacks, buildings, and similar structures with one-inch
zinc-coated rigid steel conduit stems using standard tees and elbows,
except that where lowering devices are required, equipment shall be
installed in accordance with manufacturer's recommendations.
SECTION 16525A
Page 33
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