least one additional down conductor.] [H-shaped structure, at least two
additional down conductors.] [Wing built structure, at least one
additional down conductor for each wing.] [Irregularly shaped structures,
provide enough conductors so that the average distance between them along
the perimeter is not greater than 30 m 100 feet.] [Structures exceeding 15
m 50 feet in height, provide at least one additional down conductor for
each additional 18 m 60 feet of height or fraction thereof, except that
this application will not cause down conductors to be placed about the
perimeter of the structure at intervals of less than 15 m 50 feet.]
Install additional down conductors when necessary to avoid "dead ends" or
branch conductors exceeding 5 m 16 feet in length, ending at air terminals.
Equally and symmetrically spaced down conductors about the perimeter of
the structure. Protect conductors where necessary, to prevent physical
damage or displacement to the conductor.
3.1.4
Interconnection of Metallic Parts
Connect metal doors, windows, and gutters directly to ground or down
conductors using not smaller than No. 6 copper conductor, or equivalent.
Where there is probability of unusual wear, mechanical injury, or
corrosion, provide conductors with greater electrical capacity than normal
or protect the conductor. Provide mechanical ties or pressure connectors
between grounds and metal doors and windows.
3.1.5
Ground Connections
Securely connect conductor forming continuations of down conductors from
structure to grounding electrode in a manner to ensure electrical
continuity between the two. Provide clamp type connections or welds
(including exothermic) for continuation. Provide a ground connection for
each down conductor. Attach down conductors to ground [rods] [plates] by
welding (including exothermic), brazing, or clamping. Provide clamps
suitable for direct burial. Protect ground connection from mechanical
injury. Bond metal water pipes and other large underground metallic
objects together with all grounding mediums. In making ground connections,
take advantage of all permanently moist places where practicable, although
avoid such places when area is wet with waste water that contains chemical
substances, especially those corrosive to metal.
3.1.6
Grounding Electrodes
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NOTE: Where soil conditions indicate definitely
that a ground loop will not be required, all
references to a ground loop should be deleted from
the specifications.
In accordance with MIL-HDBK-1004/6, the maximum
ground resistance for any lighting protection system
should not exceed 10 ohms.
**************************************************************************
Provide grounding electrode for each down conductor. Extend driven ground
rods into the existing undisturbed earth for a distance of not less 3050 mm
10 feet. Set ground rods not less than 610 mm 2 feet nor more than 3050 mm
10 feet, from the structure. After the completed installation, measure the
total resistance to ground using the fall-of-potential method described in
IEEE Std 81. Maximum resistance of a driven ground rod shall be [10]
[_____] ohms, under normally dry conditions [when a ground loop is not
SECTION 13100N
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