Page P-2
LIGHTNING PROTECTION AND GROUNDING
Repair and Service Manual
Read all of Section B and this section before attempting any procedure. Pay particular attention to all Notes, Cautions and Warnings.
B
GS-726-006
EFFECTIVE:
10/19/92
REVISION:
A
SUPERCEDES:
TITLE:
General Specification: Lightning Protection and Grounding
Rev -, ECN 027194
6. External Grounding Requirements
For optimum results, earth electrode installation must be accomplished early in the construction of a new site. The earth
electrode system should be established at the same time utilities are installed to insure proper interconnection of all utility
grounds/systems.
For existing sites, the earth electrode installation shall be constructed using the most economical means possible in order
to meet the intent of this specification.
Prior to the installation or design of the ground system, a survey should be taken in order to determine the earth resistiv-
ity, types of soil or any man-made features that may have a significant effect upon the efficiency of the grounding system.
Based on the information gathered, deviations from this specification (Exceeding normal requirements) may be neces-
sary in order to achieve desired results.
7. Materials
Ground Rod Electrodes: Ground rod electrodes shall have a minimum diameter of 5/8" and be no less than 10'-0" in
length. Rods may be copper, copper-clad steel or stainless steel. Galvanized steel rods are not permitted unless it is
determined that the galvanized rod will have a longer life expectancy due to soil conditions.
Ground Rod Spacing: Ground rods shall not be spaced at intervals exceeding 60'-0" around the perimeter of the struc-
ture.
Ground Loop Conductor: In no case shall the ground loop conductor be smaller than a 2/0 AWG bare, stranded, soft
drawn copper wire. The ground loop must be installed at least 24" below grade and be at least 24" away from the struc-
ture. All bends in the conductor shall have a minimum radius of 8" and be no less than 90 degrees.
Ground Mats: In areas where electrodes cannot be driven, a ground mat consisting of a #6 solid copper or a copper-cop-
per clad steel mesh, utilizing a 12" x 12" cross pattern may be used. All inter-connections in the mesh shall be brazed or
silver soldered.
Ground Plates: Ground plates if utilized shall be 24" x 24" x .032" thick solid copper. Ground plates should only be used if
a ground rod cannot be driven.
Ground Connections: Unless otherwise specified or approved by the owner, all connections below grade shall be by exo-
thermic weld (Cadweld). Where exothermic welds may not be practical, UL approved grounding clamps that utilize two
bolts for pressure may be used. NOTE: Prior approval must be obtained in order to use a mechanical connection below
grade.
8. Earth Electrode System
The earth electrode system consists of a network of earth electrode rods, plates, mats or grids and their interconnecting
conductors. The extensions into the building are used as the principle grounding point for connecting to the ground sys-
tem serving the building. Ground potential is established by electrodes in the earth.
An electrode may be a metallic water pipe that has no isolation joints, a system of buried, driven rods interconnected with
a bare wire that normally forms a ring around the building or a ground plane of horizontal buried wires. Depending upon
soil conditions, building design and the existing water pipe networks, an electrode may be a combination of any of the
above mentioned systems.
9. Lightning Protection System
The lightning protection system provides a non-destructive path to ground for lightning energy contacting or induced onto
or in a building. To effectively protect from lightning damage, air terminals are installed according to the National Fire Pro-
tection Association Lightning Protection Code (NFPA 780). Air terminals will intercept the discharge to keep it from pene-
