Avaya MCC1, Установка и обновления

Страница: 761 / 874

Approved Grounds
SI Installation and Upgrades 761
June 2004
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-in. (1.3 cm) in diameter, in
direct contact with the earth for at least 10 ft (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-in. (1.6 cm) solid rod or 3/4-in. (2 cm) conduit or pipe electrode
driven to a minimum depth of 8 ft (2.4 m).
•
Plate electrodes
—
Must have a minimum of 2 square ft (0.185 square m) of metallic surface
exposed to the exterior soil
Concrete Encased Ground
—
An electrode encased by at least 2 in. (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 ft (6.1 m) of 1 or more steel reinforcing bars or rods 1/2-in. (1.3 cm) in
diameter, or at least 20 ft (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 ft (0.76
m) below the earth’s surface. The ground ring must be at least 20 ft (6.1 m) of 2 AWG (35 mm
2
), bare,
copper wire.