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T4000 DC Power Electrical Safety Guidelines


The following electrical safety guidelines apply to a DC-powered router:

  • 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.


    Failure to provide the required circuit breaker or current-limiting fuse for each DC power cable can cause injury or damage to equipment.

    Each 48 VDC facility DC source input power cable must be equipped with a current-limiting fuse or circuit breaker external to the Juniper Networks equipment rated at 100 A (–48 VDC) maximum for the six-input DC power supply, or as required by local code. The voltage rating of the facility DC source circuit breaker must be 80 V minimum. We recommend an 80 A circuit breaker or current-limiting fuse rated for each 60 A DC power cable. We recommend a 100 A circuit breaker or current-limiting fuse rated for each 80 A DC power cable

  • 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.

  • 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.


    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.

  • 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 60 A @ –48 VDC per input for the six-input DC power supply.

    Run two wires from the circuit breaker box to a source of 48 VDC. Use appropriate gauge wire to handle up to 80 A for 60 A DC power cables or 100 A for 80 A DC power cables. .


    Only 60 A feeds are currently supported.

  • 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.

  • 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.

  • 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.