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

GROUNDING (EARTHING) FOR SMALL, LARGE, AND MULTI-STORY BUILDINGS CHAPTER 5: INTERNAL GROUNDING (EARTHING)
5.7 GROUNDING (EARTHING) FOR SMALL, LARGE, AND MULTI-
STORY BUILDINGS
Building infrastructure encompasses telecommunication spaces, pathway, cables, connecting hardware,
and the telecommunication grounding (earthing) and bonding system (ANSI-J-STD-607-A-2002). The
information herein specifies the requirements for establishing a uniform communication grounding
system within a small, large or multistory building when an internal grounding system does not exist.
For additional information, see ANSI-J-STD-607-A-2002.
5.7.1 ESTABLISHING A COMMUNICATION GROUNDING (EARTHING)
SYSTEM
A MGB shall be properly installed as described herein and within “General Bonding Requirements” on
page 5-31. The MGB serves as the dedicated extension of the building grounding (earthing) electrode
system for the communication systems throughout the building. It also serves as a central attachment
point for the communication bonding backbone conductor(s) and the equipment. There should only be a
single MGB installed within the building. The following paragraphs are requirements of ANSI-J-STD-
607-A-2002.
NOTE: Buildings or campuses with more than one electrical service entrance, each of which serves the
communication system, require special design considerations that are beyond the scope of this
document. Consultation with Motorola Engineering or with an engineering firm specializing in
grounding system design is recommended in the instances.
The MGB shall be bonded back to the service equipment (power) ground with the shortest and
straightest routing possible. The MGB grounding conductor should be routed to provide a direct
downward flow path back to the building's grounding electrode system. If a bend is required in the
MGB grounding conductor, minimum bending radius and angle shall be adhered to.
The ideal location for the MGB is in the telecommunications entrance facility, however the MGB
should be located to minimize the length of the MGB grounding conductor back to the electrical service
(power) ground where the electrical service neutral to ground bond has been established. When a
panelboard is located within the same room as the MGB, the MGB shall be located as close to the
panelboard as practicable and it shall be installed to maintain clearances required by applicable
electrical codes. The MGB should also be located to provide the shortest and straightest routing for the
telecommunications primary SPD grounding conductor. See Figure 5-38 for an example.
5-58 68P81089E50-B 9/1/05