Specifications
Issue 6 February 2007 413
DC power converter (649A)
The 649A converts the –48 VDC from the power-distribution unit to outputs of:
● –48 VDC at 10 A,
● +5 VDC at 60 A, and
● –5 VDC at 6 A.
These outputs distribute power to circuit pack slots in the carriers.
AC and DC grounding
Approved grounds
An approved ground is the closest acceptable medium for grounding the building entrance
protector or the entrance cable shield. An approved ground is also acceptable as a single-point
ground of the system.
If more than one type of approved ground is available on the premises, bond the grounds
together. Follow the instructions in Section 250-81 of the National Electrical Code, or the
applicable electrical code in the country where the equipment is installed.
Protective grounds
Acceptable grounds include the following materials:
● Grounded building steel. The metal frame of the building where an acceptable metallic
water pipe, concrete encased ground, or a ground ring grounds the building.
● Acceptable water pipe. An underground water pipe must be at least .5 inch
(1.3 centimeter) in diameter, and in direct contact with the earth for at least 10 feet (3
meters). The pipe must be electrically continuous to the point where the protector ground
wire is connected. The pipe can also be made electrically continuous by bonding around
insulated joints, plastic pipe, or plastic water meters.
● Concrete encased ground. An electrode must be encased by at least 2 inches (5
centimeters) of concrete. The ground must be located within and near the bottom of a
concrete foundation or footing and is in direct contact with the earth. The electrode must
be at least 20 feet (6 meters) of one or more steel reinforcing bars or rods .5 inch (1.3
centimeter) in diameter. Or the electrode must be at least 20 feet (6 meters) of bare, solid
copper, 4 AWG (26 millimeter
2
) wire.
● Ground ring. A buried ground must encircle a building or a structure at a depth of at least
2.5 feet (0.8 meter) below the surface of the earth. The ground ring must be at least 20 feet
(6 meters) of 2 AWG (35 millimeter
2
), bare, copper wire.