Juniper QFabric QFX3000-G Hardware Documentation page 414

QFX3000-G QFabric System Hardware Documentation
DC Power Electrical Safety Guidelines
DC Power Disconnection Warning
364
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A DC-powered device is equipped with a DC terminal block that is rated for the power
requirements of a maximally configured device.
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 , the negative lead to the terminal labeled –48 VDC, and the
RTN
earth ground to the device grounding points.
WARNING: Before performing any of the DC power procedures, ensure that
power is removed from the DC circuit. To ensure that all power is off, locate
the circuit breaker on the panel board that services the DC circuit, switch the
circuit breaker to the OFF position, and tape the device handle of the circuit
breaker in the OFF position.
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