approximately midway between the top and bottom. Reduce joints in
conductors to a minimum and make joints to have the same tension strength
as the conductors that are joining. Space fasteners of copper or
copper-bronze alloy not over 915 mm 3 feetapart for vertical conductors and
not over 610 mm 2 feet apart for horizontal conductors. To prevent gases
from corroding copper air terminals, provide conductors and fasteners within
7620 mm 25 feetof the top of stack with continuous coating of hot dipped
lead or an equivalent coating. Provide conductors conforming to the
requirements for nonmetallic stacks for stacks partly or wholly of
reinforced concrete. For nonmetallic stacks, electrically connect
reinforcing steel to down conductors at top and bottom of concrete.
3.3
INTERFACE WITH OTHER STRUCTURES
3.3.1
Interconnection of Metal Bodies
Protect metal bodies when not within the zone of protection of air
terminal. Bond metal bodies having an area of 0.258 square m 400 square
inches or greater or a volume of 0.016387 cubic m 1000 cubic inches or
greater to lightning protection system using main size conductors and a
bonding plate having a surface contact area of not less than 1935 square mm
3 square inches. Make provisions to guard against the corrosive effect of
bonding dissimilar metals. Bond metal bodies at their closest point to the
lightning protection system using bonding conductors and fittings.
Independently ground any metal body that exceeds 1525 mm 5 feet in any
dimension, that is situated wholly within a building, and that does not at
any point come within 1830 mm 6 feet of a lightning conductor or metal
connected to a lightning protection system.
3.3.2
Fences
Except as specified below, metal fences that are electrically continuous
with metal posts extending at least 610 mm 2 feet into the ground require
no additional grounding. Ground other fences on each side of every gate at
gate posts, at corner posts, and at end posts. Bond gate to adjacent fence
post utilizing flexible copper grounding braid with sufficient slack to
permit 3.14 rad 180 degree opening of the gate. Provide flexible copper
ground braid which has an ampacity equivalent to that of the fence ground
wire specified herein. Provide [ground rods][grounding plates] every 305
to 457 m 1000 to 1500 feet for grounding fences when fences are located in
isolated places, and every 152 to 228 m 500 to 750 feet when in proximity (
30 m 100 feet or less) to public roads, highways, and buildings. Provide
connection to ground from the post where it is metal and is electrically
continuous with the fencing using removable ground clamps on the fence
posts and split-bolt connectors suitable for dissimilar metals on the fence
fabric and barbed wire. [Where the fence consists of wooden posts and
horizontal metal strands only, run down conductors consisting of No. 8
copper wire or equivalent from the ground rod the full height of the fences
and fastened to each wire, so as to be electrically continuous.] Make
connections to ground from the horizontal metal strand using split-bolt
connectors suitable for dissimilar metals on the fence fabric and barbed
wire. Ground metal fences at or near points 45 m 150 feet on each side of
medium and high voltage, (meaning in excess of 600 volts,) overhead line
crossings. Ground metal fences at 45 m 150 foot intervals where high and
medium voltage lines are directly overhead and run parallel to the fence.
3.3.3
Exterior Overhead Pipe Lines
Properly ground overhead pipes, conduits, and cable trays on the exterior
SECTION 13100N
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