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

STANDARDS AND GUIDELINES FOR COMMUNICATION SITES MINIMUM SITE GROUNDING (EARTHING) REQUIREMENTS
4.7.8 OUTDOOR CABINET GROUNDING (EARTHING)
Outdoor cabinets are grounded (earthed) in a very similar manner as a dedicated communications
building (ANSI T1.313-2003, section 1.1). See “Dedicated Communications Building Grounding
(Earthing)” on page 4-59 for details.
Outdoor cabinets shall be grounded as follows:
• The cabinet shall be encircled with a ground ring. The ground ring shall meet the requirements
defined in “External Building and Tower Ground Ring” on page 4-22.
• The ground ring shall be installed at least 610 mm (2 ft.) from the cabinet foundation/pad.
• The cabinet ground ring shall have a ground rod installed at each corner and as needed to limit the
distance between rods from 3 m to 4.6 m (10 to 15 ft.). Ground rods shall have a minimum
separation from other ground rods equal to its length (ANSI T1.313-2003).
• The cabinet ground ring shall bond to the tower ground ring as detailed in “External Building and
Tower Ground Ring” on page 4-22.
• Towers associated with outdoor cabinets shall be grounded as detailed in “Tower Grounding
(Earthing)” on page 4-50.
• RF transmission lines shall be grounded/bonded as detailed in “RF Transmission Line and
Preamplifier Grounding (Earthing)” on page 4-62.
• Metallic objects near the cabinet shall be bonded to the cabinet grounding electrode system as
detailed in “Metallic Objects Requiring Bonding” on page 4-67.
• The cabinet grounding electrode system shall bond to the cabinet's internal ground point and
cabinet housing using a 35 mm 2 csa (#2 AWG) or coarser, tinned or un-tinned, copper conductor.
The conductor shall be run in a direct manner with no sharp bends or narrow loops (ANSI T1.313-
2003, section 11.3, and ANSI T1.334-2002, section 13.4). See “Bending And Routing Grounding
(Earthing) Conductors” on page 4-29.
In addition to the above requirements, the follow recommendations should be considered:
• Cabinets installed on pads that incorporate a footing should consider the use of concrete encased
electrodes, in addition to the ground ring. See “Concrete-Encased Electrodes” on page 4-20.
• Depending on the location of the cabinet's internal ground point, the grounding conductor installed
between the grounding electrode system and the cabinet's internal ground point may need to be
routed through the concrete footing/pad in order to allow conductor routing in a direct manner. This
requires the grounding conductor to be installed before the concrete is poured.
68P81089E50-B 9/1/05 4-61