DC Power Supply in EX4300 Switches

Characteristics of a DC Power Supply

EX4300 switches support 550 W DC power supply (see Figure 1).

Figure 1: DC Power Supply for an EX4300 Switch

You can install up to two DC power supplies in an EX4300 switch. Power supplies are installed in the power supply slots labeled PSU 0 and PSU 1 in the rear panel of the chassis.

Table 1 lists the details of the 550 W DC power supplies used in EX4300 switches.

To prevent electrical injury while installing or removing DC power supplies, carefully follow instructions in Installing a DC Power Supply in an EX4300 Switch and Removing an AC Power Supply from an EX4300 Switch.

DC Power Supply Airflow

Each power supply has its own fan and is cooled by its own internal cooling system.

Each power supply has a label AIR OUT (AFO) or AIR IN (AFI) on the faceplate of the power supply that indicates the direction of airflow in the power supply.

Table 2 lists the DC power supply models and the direction of airflow in them.

N+0 Redundancy Configuration of DC Power Supplies

In an N+0 redundancy configuration, no power is reserved for resiliency regardless of number of power supplies installed in the switch.

Depending on the power supplies installed in the switch, you can determine the system power budget.

• If one power supply is installed in the switch:

  System power budget = Output wattage of the installed power supply (PSU(W))

• If two power supplies are installed in the switch:System power budget = (Sum of the output wattage of the two power supplies) – (10% of the output wattage of the installed power supply)

  System power budget = PSU₀(W) + PSU₁(W) – (0.10 x (PSU(W))

Table 3 lists the N+0 power calculation for EX4300 switches that use 550 W DC power supplies.

N+N Redundancy Configuration of DC Power Supplies

You can configure your switch for N+N redundancy, in which N power supplies can be removed or fail and the remaining N power supplies continue to supply power for the switch without interruption.

You can configure the power management software to manage switch power for N+N redundancy. When you configure power management for N+N redundancy, half of the total power available (N) is held as reserve power while the other half (N) is available for immediate consumption. If the switch configuration changes and requires additional power, then additional power is drawn from the reserve power, and the switch no longer has N+N power supply redundancy. This condition raises a minor alarm. If the condition is not corrected within 5 minutes, then a major alarm is issued.

For more information about how power management allocates power to chassis components when power is insufficient, see Understanding Power Management on EX Series Switches.

Depending on the power supplies installed in the switch, you can determine the system power budget.

• If one power supply is installed in the switch:

  • System power budget = Output wattage of the installed power supply (PSU(W))

  • Backup power available = 0 W

  A minor alarm is raised as switch has no N+N power supply redundancy.

• If two power supplies are installed in the switch:

  • System power budget = (Output wattage of one power supply) – (5% of the output wattage of one power supply)

    System power budget = PSU(W) – (0.05 x PSU(W))

  • Backup power available = (Output wattage of one power supply) – (5% of the output wattage of one power supply)

    System power budget = PSU(W) – (0.05 x PSU(W))

Table 4 lists the N+N power calculation for EX4300 switches that use 550 W DC power supplies.