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DEFINITY Enterprise Communications Server Release 6
Installation and Test for Multi-Carrier Cabinets
555-230-112
Issue 5
May 1998
Install and Connect Cabinets
Page 1-23Approved Grounds
1
Approved Grounds
An approved ground is the closest acceptable medium for grounding the
building entrance protector, entrance cable shield, or single-point ground of
electronic telephony equipment. If more than 1 type of approved ground is
available on the premises, the grounds must be bonded together as required in
Section 250-81 of the National Electrical Code.
Grounded Building Steel
— The metal frame of the building where it is
effectively grounded by 1 of the following grounds: acceptable metallic water
pipe, concrete encased ground, or a ground ring.
Acceptable Water Pipe
— A metal underground water pipe, at least 1/2-inch
(1.3 cm) in diameter, in direct contact with the earth for at least 10 feet (3 m). The
pipe must be electrically continuous (or made electrically continuous by bonding
around insulated joints, plastic pipe, or plastic water meters) to the point where
the protector ground wire connects. A metallic underground water pipe must be
supplemented by the metal frame of the building, a concrete encased ground, or
a ground ring. If these grounds are not available, the water pipe ground can be
supplemented by 1 of the following types of grounds:
■ Other local metal underground systems or structures — Local
underground structures such as tanks and piping systems
■ Rod and pipe electrodes — A 5/8-inch (1.6 cm) solid rod or 3/4-inch (2
cm) conduit or pipe electrode driven to a minimum depth of 8 feet (2.4 m).
■ Plate electrodes — Must have a minimum of 2 square feet
(0.185 square m) of metallic surface exposed to the exterior soil
Concrete Encased Ground
— An electrode encased by at least 2 inches
(5.1 cm) of concrete and located within and near the bottom of a concrete
foundation or footing in direct contact with the earth. The electrode must be at
least 20 feet (6.1 m) of 1 or more steel reinforcing bars or rods 1/2-inch (1.3 cm)
in diameter, or at least 20 feet (6.1 m) of bare, solid copper, 4 AWG (26 mm
2
)
wire.
Ground Ring
— A buried ground that encircles a building or structure at a depth
of at least 2.5 feet (0.76 m) below the earth’s surface. The ground ring must be at
least 20 feet (6.1 m) of 2 AWG (35 mm
2
), bare, copper wire.