AT&T 555-230-894 User Manual
Approved Grounds
A-2
Issue 1 September 1995
encased ground, or a ground ring. If these grounds are not available, the water
pipe ground can be supplemented by one of the following types of grounds:
pipe ground can be supplemented by one of the following types of grounds:
■
Other local metal underground systems or structures — Local
underground structures such as tanks and piping systems
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
(1.9 cm) (conduit or pipe) electrode driven to a minimum depth of 8 feet
(2.5 meters)
(1.9 cm) (conduit or pipe) electrode driven to a minimum depth of 8 feet
(2.5 meters)
■
Plate electrodes — Must have a minimum of 2 square feet (0.6 sq. meter)
of metallic surface exposed to the exterior soil
of metallic surface exposed to the exterior soil
Concrete Encased Ground.
— An electrode encased by at least 2 inches
(5 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 meters) of one or more steel reinforc ing bars or rods 1/2 inch
(1.3 cm) in diameter, or at least 20 feet (6 meters) of bare, solid copper,
4 AWG wire.
foundation or footing in direct contact with the earth. The electrode must be at
least 20 feet (6 meters) of one or more steel reinforc ing bars or rods 1/2 inch
(1.3 cm) in diameter, or at least 20 feet (6 meters) of bare, solid copper,
4 AWG wire.
Ground Ring.
— A buried ground that encircles a building or structure at a
depth of at least 2-1/2 feet (0.8 meter) below the earth's surface. The ground ring
must be at least 20 feet (6 meters) of 2-AWG, bare, copper wire.
must be at least 20 feet (6 meters) of 2-AWG, bare, copper wire.
Approved Floor Grounds
Approved floor grounds are those grounds on the floor of each high-rise building
suitable for connection to the ground terminal in the riser closet and to the Private
Branch Exchange (PBX) equipment single-point ground terminal. Approved floor
grounds may include the following:
suitable for connection to the ground terminal in the riser closet and to the Private
Branch Exchange (PBX) equipment single-point ground terminal. Approved floor
grounds may include the following:
■
Building steel
■
The grounding conductor for the secondary side of the power transformer
feeding the floor
feeding the floor
■
Metallic water pipes
■
Power feed metallic conduit supplying panel boards on the floor
■
A grounding point specifically provided in the building for the purpose
!
WARNING:
If the approved ground or approved floor ground can only be accessed
inside a dedicated power equipment room, then connections to this ground
should be made by a licensed electrician.
inside a dedicated power equipment room, then connections to this ground
should be made by a licensed electrician.
NOTE:
All protective grounds must be electrically connected together to form a
single grounding electrode system.
single grounding electrode system.