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GROUNDING (EARTHING) ELECTRODE SYSTEM COMPONENT AND INSTALLATION REQUIREMENTS CHAPTER 4: EXTERNAL GROUNDING (EARTHING)
4.4.2.3 PROTECTING AND SECURING GROUNDING (EARTHING) CONDUCTORS
Above ground external grounding (earthing) conductors, including straps, are exposed to movement by
wind and other physical forces that can lead to damage or breakage over time. The following
requirements shall apply when installing grounding conductors:
• Grounding conductors shall be protected where exposed to physical damage (NFPA 70-2005,
Articles 250.64, 800.100, 810.20, 820.100; and NFPA 780-2004, section 4.9.11).
• Grounding conductors exposed to physical damage shall be protected for a minimum distance of
1.8 m (6 ft.) above grade level (NFPA 780-2004, section 4.9.11.2). Such areas may include, but are
not limited to, runways, driveways, school playgrounds, cattle yards, public walks (NFPA 780-
2004, section 4.9.11).
• Metallic guards and/or conduits used to protect grounding conductors shall be bonded to the
grounding conductor at both ends (NFPA 70-2005, Article 250.64 and NFPA 780-2004, section
4.9.11.1).
• The grounding conductor or its enclosure shall be securely fastened to the surface on which it is
carried (NFPA 70-2005, Articles 250.64 and 810.21; and NFPA 780-2004, section 4.10).
• Grounding conductors shall be secured using appropriate hardware intended for the purpose.
• When metallic fasteners are used on bare grounding conductors, fasteners of the same material
shall be used, or approved bonding techniques shall be observed for the connection of dissimilar
metals. See “Dissimilar Metals and Corrosion Control” on page 4-34. See NFPA 780-2004, section
4.10.2 for additional information.
• Above ground grounding conductors shall be securely fastened at intervals not exceeding 91 cm
(3 ft.) where practical. (ANSI T1.334-2002, section 8.3 and NFPA 780-2004, Section 4.10)
4.4.3 EXTERNAL GROUND BUS BAR
The purpose of the external ground bus bar (EGB) is to provide a convenient grounding (earthing)
termination point for antenna transmission lines (coaxial cables) and other cables prior to their entry
into a building or shelter (ANSI T1.313-2003). Antenna transmission lines and other communications
cables with metallic sheaths shall be grounded as close as practical to their point of entry into the
building or shelter (NFPA 70-2005, articles 770.93, 800.100, 810.20, 820.93, and 820.100).
Requirements for external ground bus bars, when used, are listed below:
• The EGB shall be constructed and minimally sized in accordance with Table 4-3 on page 4-32,
ensuring the ground bus bar is large enough to accommodate all transmission lines and other
grounding connections.
• The EGB shall be designed for the purpose of grounding and should be UL listed,
• The EGB shall be installed at the point where the antenna transmission lines and other
communications cables enter the building or shelter.
• The EGB shall be connected directly to the grounding electrode system using a downward run of
35 mm2 csa (#2 AWG) or coarser, bare, solid or stranded, tinned or un-tinned, copper conductor; it
is recommended to use a larger conductor, such as 120 mm 2 (#4/0 AWG) (United States National
Weather Service Manual 30-4106-2004, “Lightning Protection, Grounding, Bonding, Shielding,
and Surge Protection Requirements”). See Figure 4-23. The grounding conductor shall be installed
in a direct manner with no sharp bends or narrow loops. (See “Bending And Routing Grounding
(Earthing) Conductors” on page 4-29.)
4-30 68P81089E50-B 9/1/05