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Connecting DC Power to an EX 8200 series Switch

An EX 8200 series switch can be configured with up to six DC power supplies. After you have installed at least one power supply, you can connect power to the switch.

Warning: Before performing DC power procedures, ensure that power is removed from the DC circuit. To ensure that all power is off, locate the circuit breaker on the panel board that services the DC circuit, switch the circuit breaker to the off position, and tape the switch handle of the circuit breaker in the off position.

Note: DC power supplies are not supported on EX 8208 switches currently.

Caution: Before you connect power to the switch, 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 switch (for example, by causing a short circuit).

Caution: Mixing different types of power supplies in the same chassis is not a supported configuration.

Note: A DC power supply requires a dedicated 100 A circuit breaker for each input DC feed.

Note: Each power supply input feed must be connected to a dedicated DC power source outlet.

Before you begin connecting DC power to an EX 8200 series switch:

  • Ensure that you have taken the necessary precautions to prevent ESD damage (see Prevention of Electrostatic Discharge Damage on EX-series Switches).
  • Ensure that you have connected the switch chassis to earth ground.

    Caution: To meet safety and electromagnetic interference (EMI) requirements and to ensure proper operation, you must connect EX 8200 series switches to earth ground before you connect them 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 earth ground. For instructions on connecting an EX 8200 series switch to ground using a separate grounding conductor, see Connecting Earth Ground to an EX-series Switch.

  • Install the power supply in the chassis. See Installing a DC Power Supply in an EX 8200 series Switch.

Ensure that you have the following parts and tools available to connect DC power to an EX 8200 series switch:

  • Electrostatic discharge (ESD) grounding strap
  • DC power source cables (not provided) with provided cable lugs attached. The provided cable lugs are sized for 2 AWG (33.6 mm2) power source cables. The DC power source cables that you provide must be 2 AWG (33.6 mm2) , minimum 60°C wire. We recommend that you install heat-shrink tubing insulation around the power cables and lugs.
  • 3/8 in. (9.5 mm) nut driver or socket wrench
  • Phillips (+) screwdriver, number 2
  • Multimeter

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

To connect DC power to an EX 8200 series switch:

  1. Attach the electrostatic discharge (ESD) grounding strap to your bare wrist, and connect the strap to the ESD point on the chassis.
  2. Flip the Enable switch on the power supply faceplate to the Standby position.

    Note: It might be necessary to slide each power supply partially out of the chassis, in order to easily connect the DC power source cables to the DC power input terminals. See Removing a DC Power Supply from an EX 8200 series Switch.

  3. Remove the plastic cable cover from the DC power input terminals, using the number 2 Phillips (+) screwdriver to loosen the screw (see Figure 1).

    Figure 1: Removing the Plastic Cable Cover on a DC Power Supply in an EX 8200 series Switch

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  4. Remove the washers and nuts from each DC power input terminal, using the 3/8-in. (9.5 mm) nut driver or socket wrench to loosen the nuts. Leave the bolts installed on the input terminals.
  5. Ensure that the power source circuit breaker is open so that the voltage across the DC power source cable leads is 0 V and that the cable leads do not become active while you are connecting DC power.
  6. 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 high resistance (indicating an open circuit) to chassis ground is negative (–) and will be installed on the –48V (input) DC power input terminal.
    • The cable with very low resistance (indicating a closed circuit) to chassis ground is positive (+) and will be installed on the RTN (return) 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.

  7. Install each power cable lug on the DC power input terminal, securing it first with a locking washer, then with the nut (see Figure 2). Apply between 29 in.-lb (3.3 Nm) and 31 in.-lb (3.5 Nm) of torque to each nut. (Use the 3/8-in. [9.5 mm] nut driver or socket wrench.)
    1. Secure each positive (+) DC source power cable lug to the RTN (return) DC power input terminal.
    2. Secure each negative (–) DC source power cable lug to the –48V (input) DC power input terminal.

    Each power supply has two independent sets of DC power input terminals (A: –48V A: RTN and B: – 48V B: RTN ). For feed redundancy, each power supply should be powered by dedicated power feeds derived from feed A and feed B. This configuration provides the commonly deployed A/B feed redundancy for the switch.

    Note: If the power cord tray is installed, you can thread the DC power cables through the power cord tray.

    Figure 2: Connecting the Power Supply Cables to an EX 8200 series Switch

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  8. Install the plastic cable cover over each set of power cables, using the number 2 Phillips (+) screwdriver to tighten the screw (see Figure 3).

    Figure 3: Installing the Plastic Cable Cover on a DC Power Supply in an EX 8200 series Switch

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  9. Ensure that the power supply is fully inserted and latched securely in the chassis. See Installing a DC Power Supply in an EX 8200 series Switch.
  10. Repeat Steps Step 2 through Step 9 for the remaining power supplies.

Updated: 2009-04-09

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