standards and guidelines for communication sites - Radio And ...
standards and guidelines for communication sites - Radio And ... standards and guidelines for communication sites - Radio And ...
SPECIAL GROUNDING (EARTHING) SITUATIONS CHAPTER 4: EXTERNAL GROUNDING (EARTHING) FIGURE 4-63 GROUNDING METAL SHIPPING CONTAINERS 4.10.5 GROUNDING (EARTHING) ELECTRODE SYSTEMS COVERED BY CONCRETE OR ASPHALT When installing a grounding (earthing) electrode system, every attempt should be made to ensure that the surface area above the grounding electrode system is not covered with concrete or asphalt. Areas covered with concrete or asphalt will dry out over time, therefore increasing the resistance to earth of the grounding electrode system. (See MIL-HDBK-419A for additional information.) Some alternatives to covering the area with concrete and asphalt are listed below: • Cover the area with gravel. • Landscape the area. • Use electrolytic ground rods when the area must be covered with concrete or asphalt. 4.11 SPECIAL GROUNDING (EARTHING) SITUATIONS EXOTHERMICALLY WELD EACH CORNER TO GROUND RING. Site conditions such as limited area and high (poor) soil resistivity can sometimes require special consideration for effective grounding (earthing). Some methods for achieving an effective grounding electrode system in some common applications are described below in the following sections. Consultation with Motorola Engineering or other engineering firm may be required in some situations. 4-88 68P81089E50-B 9/1/05
STANDARDS AND GUIDELINES FOR COMMUNICATION SITES SPECIAL GROUNDING (EARTHING) SITUATIONS 4.11.1 ROOFTOP AND INTEGRATED COMMUNICATIONS SITES Rooftop and integrated communications sites (high-rise buildings) may require special techniques for achieving a suitable grounding (earthing) electrode system when effectively grounded structural steel is not available and when encircling the building with a ground ring would not be feasible, such as in a downtown metropolitan location. Some options may be: • Consult with Motorola Engineering or other engineering firm. • Installation of a small ground ring in an available location. See Figure 4-64. • Installation of multiple parallel rods in a straight line. See Figure 4-65. • Installation of electrolytic ground rod systems. IMPORTANT: If a supplemental grounding electrode system is installed, it shall be bonded to the existing building grounding electrode system. See “Common Grounding (Earthing)” on page 4-5 NOTE: In order to maintain maximum efficiency of parallel ground rods, the ground rods shall be separated from one another by twice the length of the individual ground rods. EXTERIOR WWALL EXOTHERMICALLY LY WELDED OR HIGH-COMPRESSION CONDUCTOR BOND GROUND ROD BOND RECOMMENDED MINIMUM GROUND ROD SEPARA P ATION IS 4.9 m (16 ft.) CONDUCTOR PVC CONDUIT T GUARD 32 mm (1.25 in.) x 2.1 m (7 ft.) CABLE FASTENERS F INSTALLED T EVER Y 914 mm (3 ft.) PVC EXTENDED 305 mm (1 ft.) BELOW FINISHED GRADE GROUND RING FIGURE 4-64 SMALL GROUND RING INSTALLATION BOND BETWEEN SMALL GROUND RING AND EXISTING GROUNDING ELECTRODE SYSTEM 68P81089E50-B 9/1/05 4-89
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SPECIAL GROUNDING (EARTHING) SITUATIONS CHAPTER 4: EXTERNAL GROUNDING (EARTHING)<br />
FIGURE 4-63 GROUNDING METAL SHIPPING CONTAINERS<br />
4.10.5 GROUNDING (EARTHING) ELECTRODE SYSTEMS COVERED BY<br />
CONCRETE OR ASPHALT<br />
When installing a grounding (earthing) electrode system, every attempt should be made to ensure that<br />
the surface area above the grounding electrode system is not covered with concrete or asphalt. Areas<br />
covered with concrete or asphalt will dry out over time, there<strong>for</strong>e increasing the resistance to earth of<br />
the grounding electrode system. (See MIL-HDBK-419A <strong>for</strong> additional in<strong>for</strong>mation.) Some alternatives<br />
to covering the area with concrete <strong>and</strong> asphalt are listed below:<br />
• Cover the area with gravel.<br />
• L<strong>and</strong>scape the area.<br />
• Use electrolytic ground rods when the area must be covered with concrete or asphalt.<br />
4.11 SPECIAL GROUNDING (EARTHING) SITUATIONS<br />
EXOTHERMICALLY WELD<br />
EACH CORNER TO<br />
GROUND RING.<br />
Site conditions such as limited area <strong>and</strong> high (poor) soil resistivity can sometimes require special<br />
consideration <strong>for</strong> effective grounding (earthing). Some methods <strong>for</strong> achieving an effective grounding<br />
electrode system in some common applications are described below in the following sections.<br />
Consultation with Motorola Engineering or other engineering firm may be required in some situations.<br />
4-88 68P81089E50-B 9/1/05
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