Juniper EX2200 Series Hardware Manual page 205

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Copyright © 2011, Juniper Networks, Inc.
A DC-powered device is equipped with a DC terminal block that is rated for the power
requirements of a maximally configured device.
NOTE: To supply sufficient power, terminate the DC input wiring on a facility
DC source that is capable of supplying:
Minimum of 7.5 A at –48 VDC for EX2200 and EX3300 switches
Minimum of 8 A at –48 VDC for EX3200 and EX4200 switches
Minimum of 50 A at –48 VDC for EX6210 switches
Minimum of 60 A at –48 VDC for EX8208 switches
Minimum of 100 A at –48 VDC for EX8216 switches
Incorporate an easily accessible disconnect device into the facility wiring. Be sure to
connect the ground wire or conduit to a solid office earth ground. A closed loop ring is
recommended for terminating the ground conductor at the ground stud.
Run two wires from the circuit breaker box to a source of 48 VDC.
A DC-powered device that is equipped with a DC terminal block is intended only for
installation in a restricted access location. In the United States, a restricted access
area is one in accordance with Articles 110-16, 110-17, and 110-18 of the National Electrical
Code ANSI/NFPA 70.
NOTE: Primary overcurrent protection is provided by the building circuit
breaker. This breaker must protect against excess currents, short circuits,
and earth grounding faults in accordance with NEC ANSI/NFPA 70.
Ensure that the polarity of the DC input wiring is correct. Under certain conditions,
connections with reversed polarity might trip the primary circuit breaker or damage
the equipment.
For personal safety, connect the green and yellow wire to safety (earth) ground at both
the device and the supply side of the DC wiring.
The marked input voltage of –48 VDC for a DC-powered device is the nominal voltage
associated with the battery circuit, and any higher voltages are only to be associated
with float voltages for the charging function.
Because the device is a positive ground system, you must connect the positive lead to
the terminal labeled RTN, the negative lead to the terminal labeled –48 VDC, and the
earth ground to the device grounding points.
General Safety Guidelines and Warnings on page 155
General Electrical Safety Guidelines and Warnings on page 179
DC Power Disconnection Warning on page 186
Chapter 18: Power and Electrical Safety Information
185