Mx240 Dc Power Electrical Safety Guidelines - Juniper MX240 Hardware Manual

MX240 DC Power Electrical Safety Guidelines

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, the negative lead to the terminal labeled –48V, and the earth ground to the chassis grounding
points.
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