Mx240 Dc Power Electrical Safety Guidelines - Juniper mx240 Hardware Manual

MX240 DC Power Electrical Safety Guidelines

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Copyright © 2016, Juniper Networks, Inc.
The following electrical safety guidelines apply to a DC-powered router:
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 33.3 A @
–48 VDC per input for each power supply. We recommend that the 48 VDC facility
DC source should be equipped with a circuit breaker rated at 40 A (–48 VDC) 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.
Run two wires from the circuit breaker box to a source of 48 VDC. Use appropriate
gauge wire to handle up to 40 A.
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.
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 RTN
ground to the chassis grounding points.
DC Power Electrical Safety Warnings for Juniper Networks Devices on page 446
Chapter 39: Electrical Safety Guidelines and Warnings
, the negative lead to the terminal labeled –48V , and the earth
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