Juniper SRX550, Hardware Manual

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A DC-powered services gateway is equipped with a DC terminal block that is rated for the power
requirements of a maximally configured services gateway. To supply sufficient power, terminate the DC
input wiring on a facility DC source capable of supplying at least 65 A at –48 VDC for the system, or at
least 48 A at –48 VDC for each power supply. We recommend that the 48 VDC facility DC source be
equipped with a circuit breaker rated at 60 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 USA 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.
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Run two wires from the circuit breaker box to a source of 48 VDC. Use appropriate gauge wire to handle
up to 60 A.
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A DC-powered services gateway 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.
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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.
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For personal safety, connect the green and yellow wire to safety (earth) ground at both the services
gateway and the supply side of the DC wiring.
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The marked input voltage of –48 VDC for a DC-powered services gateway 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.
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Because the services gateway is a positive ground system, you must connect the positive lead to the
terminal labeled RETURN, the negative lead to the terminal labeled –48V, and the earth ground to the
chassis grounding points.
DC Power Disconnection Warning
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