Juniper M120 Hardware Manual page 374

M120 Multiservice Edge Router Hardware Guide
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348
A DC-powered router is equipped with a DC terminal block that is rated for the power
requirements of a maximally configured router. To supply sufficient power, terminate
the DC input wiring on a facility DC source capable of supplying at least 60 A @ –48 VDC
for the system. We recommend that the 48 VDC facility DC source be equipped with
a circuit breaker rated at 125% of the power provisioned for the input minimum, or as
required by local code. Incorporate an easily accessible disconnect device into the
facility wiring. In the United States and Canada, the –48 VDC facility should be equipped
with a circuit breaker rated a minimum of 125% of the power provisioned for the input
in accordance with the National Electrical Code in the US and the Canadian Electrical
Code in Canada. 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. Use appropriate
gauge wire to handle up to 60 A.
A DC-powered router 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 should protect against excess currents, short circuits,
and earth faults in accordance with NEC ANSI/NFPA70.
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 router and the supply side of the DC wiring.
The marked input voltage of –48 VDC for a DC-powered router 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 router is a positive ground system, you must connect the positive lead to
the terminal labeled
RETURN
earth ground to the chassis grounding points.
M120 DC Power Supply Description on page 72
Installing an M120 DC Power Supply on page 248
Replacing an M120 DC Power Supply on page 245
Replacing an M120 DC Power Supply Cable on page 251
, the negative lead to the terminal labeled
Copyright © 2018, Juniper Networks, Inc.
, and the
–48V