Technical Documentation

Disconnecting and Connecting DC Power on the M40e Router

On a DC-powered router, the power cables from the external DC power sources connect to terminal studs on the circuit breaker box located at the lower right rear of the chassis. To disconnect or connect power to the router, perform the following procedures. Also follow these procedures when replacing the power cables:

Disconnecting DC Power from the M40e Router

To disconnect DC power from the router (see Figure 1):

  1. On the console or other management device connected to the master Routing Engine, enter CLI operational mode and issue the following command to shut down the router software. (If two Routing Engines are installed, also issue the command on the backup Routing Engine.)

    user@host> request system halt

    Wait until a message appears on the console confirming that the operating system has halted.

    For more information about the command, see the Junos System Basics and Services Command Reference.

    Note: The SFM might continue forwarding traffic for approximately 5 minutes after the request system halt command has been issued.

  2. For each power supply, press the power switch on the circuit breaker box to the OFF (O) position.

    Note: If you are power cycling the power supply rather than shutting it off for a time, wait at least 60 seconds after turning it off before turning it back on. If you need to power it off again, wait for at least 60 seconds after powering it on.

  3. Shut off the power flowing from both external power sources, so that the voltage across the leads of the power cables is 0 V. Ensure that there is no chance that the cable leads might become active during the procedure.
  4. Using a Phillips screwdriver, loosen and remove the screws securing the protective shield over the terminal studs on the circuit breaker box. Remove the cover.
  5. Using a 7/16-in. nut driver or wrench, loosen the outer nut securing the cable lug to each terminal stud. Remove the outer nuts and washers, leaving the inner nut and washer on each stud.
  6. Slide the cable lug off of each terminal stud. Leave the inner washer and nut on each stud.
  7. If you are decommissioning the router, loosen and remove the screws that secure the grounding lug to the chassis and remove the grounding lug.
  8. If not immediately attaching replacement cables, replace the protective shield on the circuit breaker box and tighten the screws that secure it to the box.
  9. Verify that the removed cables are not touching or blocking access to any router components.

Figure 1: Disconnecting DC Power Cables

Image g001226.gif

Connecting DC Power to the M40e Router

Connect DC power to the router by attaching power cables from external power sources to the terminal studs on the circuit breaker box. Power cables are not supplied with the router. For DC power cable specifications, see M40e DC Power, Connection, and Cable Specifications.

Note: The router must be connected to at least two separate external DC power sources.

Caution: You must ensure that power connections maintain the proper polarity. The power source cables might be labeled (+) and (–) to indicate their polarity. There is no standard color coding for DC power cables. The color coding used by the external DC power source at your site determines the color coding for the leads on the power cables that attach to the terminal studs on the circuit breaker box.

To connect DC power to the router (see Figure 2):

  1. Verify that there is no power flowing from either external power source, so that the voltage across the leads of the power cables is 0 V. Ensure that there is no chance that the cable leads might become active during the procedure.
  2. For each power supply, verify that the power switch on the circuit breaker box is in the OFF (O) position.
  3. Using a Phillips screwdriver, loosen and remove the screws securing the protective shield over the terminal studs on the circuit breaker box. Remove the cover.
  4. Install one flat washer and one nut (in that order) on each power terminal stud:
    • If no washers and nuts are already installed, they should be in the accessory box.
    • If two pairs of nuts and washers are installed on the studs, use a 7/16-in. nut driver or wrench to loosen the outer nut on each stud. Remove the outer nuts and washers, leaving the inner nut and washer on each stud.

      Caution: The inner washer and nut prevent direct contact between the power cable lug and the circuit breaker box, which can cause a short circuit.

  5. Slide the power cable lugs onto the terminal studs. Install another washer and nut (in that order) on each terminal stud to secure each power cable lug.
    1. Connect the positive (+) source cable lugs to the return terminals, which are labeled RTN(+).
    2. Connect the negative (–) source cable lugs to the input terminals, which are labeled –48V.

    Using a 7/16-in. nut driver or wrench, tighten the nuts. Apply between 23 lb-in. (2.6 Nm) and 25 lb-in. (2.8 Nm) of torque to each nut.

  6. Bend the power cables at a radius appropriate for the AWG being used and tie them together to ensure that the power cables do not obstruct any other components. To identify the minimum bend radius for each type of power cable types, see published industry standards, such as the National Electrical Code (NEC) and Insulated Cable Engineers Association (ICEA). Do not bend a power cable beyond the specified minimum bend radius.
  7. Verify that the source power cabling and the grounding cabling are correct, that they are not touching or blocking access to router components, and that they do not drape where people could trip on them.
  8. Replace the protective shield over the terminal studs and use a Phillips screwdriver to tighten the screws.
  9. Turn on the current from the power source so that voltage flows to the router.

Figure 2: Connecting DC Power Cables

Image g001226.gif


Published: 2010-08-14

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