standards and guidelines for communication sites - Radio And ...

GROUNDING (EARTHING) FOR INTEGRATED COMMUNICATION SITES CHAPTER 5: INTERNAL GROUNDING (EARTHING)
If a bonding grid is present, it should be used to bond the raised flooring system supports at each grid
node location and suspended ceiling grids, in at least four places, preferably at the corners of the
dispatch area, using bonding methods described in this chapter. Other items such as electrical
panelboards, metallic water fountains, metallic plumbing, metallic ventilation ducts and other metallic
ancillary support items shall be bonded back to the nearest bonding grid conductor with a minimum 16
mm 2 csa (#6 AWG) copper conductor of the shortest length possible.
The bonding grid should be established within the same space used to run electrical power and
communication cables to the operator positions. This space can be below a raised flooring system that
supports the operator positions, the space immediately below the structural floor supporting the operator
positions, or the space above a suspended ceiling grid system when a raised flooring system has not
been installed (ANSI T1.321-R2000).
The bonding grid shall be made from 16 mm 2 csa (#6 AWG) or coarser stranded copper conductor that
may be jacketed as allowed by the space where it will be installed. The grid node connections shall be
made using irreversible compression-type connections that are listed for the purpose. Each grid node
connection should be positioned vertically below or above (ceiling area) each cluster SSGB. The grid
nodes may be established with horizontal offsets of 1.5 m (5 ft.) or less from a cluster. Each cluster
SSGB shall be connected to its associated grid node with a minimum 16 mm 2 csa (#6 AWG) copper
conductor of the shortest and straightest length possible. The SSGB grounding conductor shall be no
greater than 3.9 m (13 ft.) in length. If greater lengths are needed, the SSGB grounding conductors and
the bonding grid conductor shall be sized up to 35 mm 2 csa (#2 AWG).
The bonding grid shall be effectively bonded to the dispatch room main collection point SSGB or MGB
with a copper bonding conductor of the same size as the bonding grid conductor. This bonding
conductor shall be bonded to the nearest bonding grid conductor with an exothermically welded or an
irreversible compression-type connection. The conductor shall be bonded to the SSGB or MGB with
exothermic welding, irreversible compression two-hole lug, or other irreversible compression means.
5.9 GROUNDING (EARTHING) FOR INTEGRATED
COMMUNICATION SITES
For communications sites located on the rooftop or within a high-rise building whose primary purpose
is something other than a communications site, connection of the communications internal grounding
(earthing) system shall be made to the building’s common grounding electrode system as described
herein and within this chapter.
The information within this section specifies the requirements for establishing an integrated
communications site grounding system on or within a high-rise building where an internal grounding
system does not exist. When communications equipment is located on or within a building with an
established grounding system, the communications equipment shall be effectively bonded back the
common bonding network (CNB) for the building. See ANSI T1-313-2003 and ANSI T1.333-2001 for
additional information on bonding to the building CBN.
At high-rise sites, connection to effectively grounded structural building steel is the preferred
connection location for the equipment room MGB. In poured concrete buildings where structural
building steel may not be an option, effectively grounded and accessible rebar may be considered for
use as a connection point. If these options are not available, use the other methods recommended within
this section.
5-68 68P81089E50-B 9/1/05