Quantcast Down Conductors

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MIL-HDBK-419A
SEE
NOTE 2
NOTES:
1- DEAD ENDS ARE NOT ACCEPTABLE ON MAIN RIDGES OR ON RIDGES OF
DORMERS OR SIDE WINGS AS HIGH OR HIGHER THAN THE MAIN RIDGE.
2 - TOTAL CONDUCTOR LENGTH NOT TO EXCEED 16 FEET.
Figure 1-22. Criteria for Dead End Coverage
Maintain a horizontal or downward course with roof conductors. Provide "U" or "V" (up and down)
e.
pockets with a down conductor from the base of the pocket (see Figure 1-23(a)) to ground or to a convenient
lead of the main down conductor.
Route conductors through or around obstructions which lie in a horizontal plane with the conductor
f.
(Figure 1-23(b) and (c)). Bends in the conductor should not include an angle of less than 90 degrees and should
maintain a radius of 8 inches or greater (Figure 1-23(d)). In particular, re-entrant loops should be avoided (1-5).
When routing around obstructions, wide gradual bends are preferred.  Other recommended practices are
illustrated in Figures 1-23(e) thru (h).
Securely attach the conductors directly to the ridge roll or roof with UL-approved fasteners every 3
g.
feet.
h.
Conductors may be coursed through air up to 0.9 meters (3 feet) without support. With an
acceptable support such as a 1.9 cm (3/4-inch) copper-clad ground rod or its equivalent, securely fastened at
each end, a conductor may be coursed up to 1.8 meters (6 feet) through air.
1.3.2.2.2 Down Conductors.
a.
Course down conductors over the extreme outer portions of the structure and separate them as far
apart as possible. Preferred locations are at diagonally opposite corners on square or rectangular structures and
symmetrically distributed around cylindrical structures.
b.
Locate down conductors as close as practical to air terminals and to the most convenient places for
attaching the conductors to the earth electrode subsystem of the structure. The down conductors should be
equally and symmetrically spaced about the perimeter of the structure.
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