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Connecting DC Power to an EX4300 Switch

EX4300 switches can be configured with up to two DC power supplies. After you install at least one power supply, you can connect power to the switch.

Caution: Do not mix:

  • AC and DC power supplies in the same chassis
  • Power supplies with different airflow labels (AIR IN (AFI) and AIR OUT (AFO)) in the same chassis.
  • Fan modules with different airflow labels (AIR IN (AFI) and AIR OUT (AFO)) in the same chassis.
  • Power supplies and fan modules with different airflow labels (AIR IN (AFI) and AIR OUT (AFO)) in the same chassis.

Before you begin connecting DC power to an EX4300 switch:

  • Ensure that you have taken the necessary precautions to prevent electrostatic discharge (ESD) damage (see Prevention of Electrostatic Discharge Damage).
  • Ensure that you have connected the switch chassis to earth ground.

    Caution: Ensure that you install the power supply module first and then install the DC input wire, before closing input breaker ON.

    Caution: Before you connect power to the device, a licensed electrician must attach a cable lug to the grounding and power cables that you supply. A cable with an incorrectly attached lug can damage the device (for example, by causing a short circuit).

    To meet safety and electromagnetic interference (EMI) requirements and to ensure proper operation, you must connect the chassis to earth ground before you connect it to power. For installations that require a separate grounding conductor to the chassis, use the protective earthing terminal on the switch chassis to connect to the earth ground. For instructions on connecting earth ground, see Connecting Earth Ground to an EX Series Switch.

  • Install the power supply in the chassis. For instructions on installing a DC power supply in an EX4300 switch, see Installing a DC Power Supply in an EX4300 Switch.

Ensure that you have the following parts and tools available:

  • DC power source cables (12–14 AWG) with ring lug (Molex 190700067 or equivalent) (not provided)
  • Phillips (+) screwdriver, number 2 (not provided)
  • Multimeter (not provided)
  • A 14 AWG (2 mm²), minimum 90°C wire grounding cable, or one permitted by the local code, with a Panduit LCC10-14BWL or equivalent grounding lug attached (not provided)
  • Two 10-32 x .25 in. screws with #10 split-lock washer (not provided)
  • Two #10 flat washers (not provided)

To connect DC power to an EX4300 switch:

  1. Attach the grounding strap to your bare wrist and to a site ESD point.

    Note: The power supply slots are at the right end of the rear panel on 24-port and 48-port switches, and at the left end on 32-port switches. Figure 59 shows how to secure ring lugs to the terminals on the DC power supply installed on 24-port or 48-port EX4300 switches. The procedure is the same for 32-port EX4300 switches.

  2. Verify that the DC power cables are correctly labeled before making connections to the power supply. In a typical power distribution scheme where the return is connected to chassis ground at the battery plant, you can use a multimeter to verify the resistance of the –48V and RTN DC cables to chassis ground:
    • The cable with very low resistance (indicating a closed circuit) to chassis ground is positive (+) and will be installed on the V+ (return) DC power input terminal.
    • The cable with very high resistance (indicating an open circuit) to chassis ground is negative (–) and will be installed on the V– (input) DC power input terminal.

    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 DC power input terminals on each power supply.

  3. Ensure that the input circuit breaker is open so that the voltage across the DC power source cable leads is 0 V and that the cable leads will not become active while you are connecting DC power.

    Note: The V+ terminals are referred to as +RTN and V– terminals are referred to as –48 V in DC Power Wiring Sequence Warning and DC Power Electrical Safety Guidelines.

  4. Ensure that the power supplies are fully inserted in the chassis.
  5. Remove the terminal block cover. The terminal block cover is a piece of clear plastic that snaps into place over the terminal block.
  6. Remove the screws on the terminals by using the screwdriver. Save the screws.

    Warning: Ensure that the power cables do not block access to switch components or drape where people can trip on them.

    Note: The DC power supply has five terminals, two positive terminals labeled V+ and two negative terminals labeled V–, for connecting the power supply to a dedicated DC power source by using the DC power source cables labeled positive (+) and negative (–), and one terminal for connecting the power supply to earth ground (see Figure 59). The V+ terminals are shunted internally together, as are the V– terminals to provide parallel current path.

  7. Connect one end of the grounding cable to a proper earth ground, such as the rack in which the switch is mounted.
  8. Place the grounding lug attached to the grounding cable over the earthing terminal on the DC power supply.
  9. Secure the grounding lug to the protective earthing terminal with the washers and screws.
  10. Dress the grounding cable and ensure that it does not touch or block access to other switch components.

    Warning: Ensure that the cable does not drape where people could trip over it.

  11. Connect each power supply to the power source. Secure power source cables to the power supplies by screwing the ring lugs attached to the cables to the appropriate terminals by using the screw from the terminals (see Figure 59).
    • To connect a power supply to a power source:
      1. Secure the ring lug of the positive (+) DC power source cable to one of the + terminals on the DC power supply.
      2. Secure the ring lug of the negative (–) DC power source cable to the – terminal adjacent to the + terminal that you connected to on the DC power supply.
      3. Connect the ground wire to earth ground if the switch is not in a grounded rack.
      4. Tighten the screws on the power supply terminals until they are snug by using the screwdriver. Do not overtighten—apply between 5 lb-in (0.56 Nm) and 6 lb-in (0.68 Nm) of torque to the screws.

      If you have a second installed power supply, connect it in the same way you did the first.

    • To connect one power supply to two power sources:
      1. Secure the ring lug of the positive (+) DC power source cable from the first DC power source to a + terminal on the power supply.
      2. Secure the ring lug of the negative (–) DC power source cable from the first DC power source to the – terminal adjacent to the + terminal on the DC power supply to which you connected the ring lug of the positive (+) DC power source cable from the first DC power source.
      3. Secure the ring lug of the positive (+) DC power source cable from the second DC power source to the other + terminal on the power supply.
      4. Secure the ring lug of the negative (–) DC power source cable from the second DC power source to the – terminal adjacent to the + terminal on the DC power supply to which you connected the ring lug of the positive (+) DC power source cable from the second DC power source.
      5. Connect the ground wire to earth ground if the switch is not in a grounded rack.
      6. Tighten the screws on the power supply terminals on both the power supplies until snug using the screwdriver. Do not overtighten—apply between 8 lb-in. (0.9 Nm) and 9  lb-in. (1.02 Nm) of torque to the screws.

      If you have a second installed power supply, connect it in the same way you did the first.

    Figure 59: Securing Ring Lugs to the Terminals on the DC Power Supply

    Securing Ring Lugs
to the Terminals on the DC Power Supply
  12. Replace the terminal block cover.
  13. Close the input circuit breaker.
  14. Verify that the IN OK and OUT OK LEDs on the power supply are lit green and are on steadily.

Related Documentation

Modified: 2015-06-23