DC Power Electrical Safety Guidelines
DC Power Electrical Safety Guidelines
The following electrical safety guidelines apply to a DC-powered services gateway:
•
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 30 A @ -48 VDC for the system. We recommend that the 48 VDC
facility DC source 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. 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 40 A.
•
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.
•
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 services gateway and the supply side of the DC wiring.
•
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.
•
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.
107Copyright © 2017, Juniper Networks, Inc.
Chapter 24: Electrical Safety Guidelines and Warnings
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