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

STANDARDS AND GUIDELINES FOR COMMUNICATION SITES GROUNDING (EARTHING) ELECTRODE SYSTEM COMPONENT AND INSTALLATION
REQUIREMENTS
GROUNDING CONDUCTOR
3 m
(10 ft.)
610 mm
(2 ft)
2.4 m
(8 ft.)
FIGURE 4-8 TYPICAL SINGLE GROUND ROD INSTALLATION
GROUNDING CONDUCTOR
RECOMMENDED DEPTH MINIMUM DEPTH
TOP OF ROD JUST
BELOW SOIL
SURFACE
• Ground rods shall not be installed closer than 1.8 m (6 ft.) from other ground rods and grounding
electrodes (NFPA 70-2005, Article 250.56). See Figure 4-31 on page 4-49 for an example.
• Unless otherwise stated in this chapter, ground rods shall not be installed closer to one another than
the sum of their respective lengths, when possible. This is especially important for the ground rods
associated with tower ground rings. See “Grounding (Earthing) Electrode Resistance
Characteristics and Sphere of Influence” on page 4-9
• See “External Building and Tower Ground Ring” on page 4-22 for ground rod installation
requirements on ground rings.
• The method of bonding grounding conductors to ground rods shall be compatible with the types of
metals being bonded (See “Dissimilar Metals and Corrosion Control” on page 4-34).
• Ground rods that cannot be driven straight down, due to contact with rock formations, may be
driven at an oblique angle of not greater than 45 degrees from the vertical, or may be buried
horizontally and perpendicular to the building, in a trench at least 762 mm (30 in.) deep, as shown
in Figure 4-9 (NFPA 70-2005, Article 250.53).
IMPORTANT: The top of a ground rod shall not be cut off if contact with rocks prevents driving of the
rod. Alternate driving techniques, as describe above, shall be used in these cases.
68P81089E50-B 9/1/05 4-13
2.4 m
(8 ft.)