Ac Power Ex8208 Requirements Calculating

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Calculating Power Requirements for an EX8208 Switch

Use the information in this topic to calculate power consumption, system thermaloutput, and number of power supplies required for different EX8208 switchconfigurations.

Before you begin these calculations:

■ Ensure you understand the different switch configurations. See EX8208 SwitchConfigurations.

■ Ensure that you know the power requirements of different EX8208 switchcomponents. See Power Requirements for EX8208 Switch Components.

This topic describes these tasks:

1. Power Consumption of Different EX8208 Switch Configurations on page 2

2. System Thermal Output for Different EX8208 Switch Configurations on page 3

3. Number of Power Supples Required for Your EX8208 SwitchConfiguration on page 4

Calculating Power Requirements for an EX8208 Switch ■ 1



Power Consumption of Different EX8208 Switch Configurations

■ To calculate the maximum internal power consumption for a base configurationEX8208 switch:

Add the individual power requirements of all components in the base switchconfiguration. See Power Requirements for EX8208 Switch Components.

Thus, power consumption = Power requirements of: Fan tray at maximumspeed + 1 SRE module + 1 SF module

= (1050 W + 180 W + 100 W)

= 1330 W

■ To calculate the maximum internal power consumption for a redundant

configuration EX8208 switch:

Add the individual power requirements of all components in the redundantswitch configuration. See Power Requirements for EX8208 Switch Components.

Thus, power consumption= Power requirements of: Fan tray at maximum speed+ 2 (SRE modules) + 1 SF module

= (1050 W + 2(180) W + 100 W)

= (1050 W + 360 W + 100 W)

= 1510 W

■ To calculate the maximum internal power consumption for a fully loaded EX8208switch configuration:

Add the individual power requirements of all components in a fully loaded switchconfiguration. See Power Requirements for EX8208 Switch Components.

Thus, power consumption = Power requirements of: Fan tray at maximumspeed + 2 (SRE modules) + 1 SF module + 8 (8-port SFP+ line cards)

= (1050 W + 2(180) W + 100 W + 8(450) W)

= (1050 W + 360 W + 100 W + 3600 W)

= 5110 W

2 ■ Power Consumption of Different EX8208 Switch Configurations



■ To calculate the maximum system power consumption for your EX8208 switchconfiguration, divide the maximum internal power consumption of the switchby the efficiency of the power supply. This accounts for the loss of energy withinthe power supply.

NOTE: The efficiency of a 2000 W power supply is approximately 90 percent wheninput voltage is high line (200–240 VAC).

The efficiency of a 2000 W power supply is approximately 87 percent when inputvoltage is low line (100–120 VAC).

To calculate the maximum system power consumption for a fully loaded EX8208switch configuration:

Divide the maximum internal power consumption of the switch by the efficiency

of the power supply when input voltage is high line (200–240 V).

Thus, maximum system power consumption = Maximum internal powerconsumption / Efficiency of the power supply

= (5110 W) / (0.90)

= 5678 W

System Thermal Output for Different EX8208 Switch Configurations

To calculate the system thermal output in British thermal units (BTU) per hour for

your switch configuration, multiply the power consumption (maximum internal ormaximum system) of the switch by 3.4.

To calculate the system thermal output for a fully loaded EX8208 switchconfiguration:

1. Compute the maximum system power consumption of a fully loadedconfiguration. See maximum system power consumption for a fully loadedconfiguration switch in “Power Consumption of Different EX8208 SwitchConfigurations” on page 2.

2. Multiply the maximum system power consumption by 3.41

= (5678 W) x (3.41)

System thermal output for a fully loaded switch configuration = 19,362 BTU/hr

NOTE: Using the maximum system power consumption values to calculate the systemthermal output often results in overprovisioning the cooling systems. Typical powerconsumption is about one-third lower than these calculated values.

System Thermal Output for Different EX8208 Switch Configurations ■ 3



Number of Power Supples Required for Your EX8208 Switch Configuration

To calculate the number of power supplies required for your switch configuration,divide the sum of the power requirements of all the components in your switch bythe output wattage of one power supply.

NOTE: If the input voltage is high line (200–220 VAC), the output wattage of a powersupply is 2000 W.

If the input voltage is low line (100–120 VAC), the output wattage of a power supplyis 1200 W.

To calculate the number of power supplies required for a fully loaded EX8208 switch

configuration when input voltage is high line:1. Compute the maximum internal power consumption for your switch

configuration. See the maximum internal power consumption of a fully loadedswitch in “Power Consumption of Different EX8208 Switch Configurations” onpage 2.

Maximum internal power consumption of a fully loaded EX8208 switchconfiguration = 5678 W

2. Divide the maximum internal power consumption by the output wattage of thepower supply. For high-line input voltage, the output wattage is 2000 W.

= (5678 W) / (2000 W)

Number of power supplies needed (N) = 3 (rounding up)

3. The required power configuration for EX8208 switches is N+1. See AC PowerSupply in an EX8200 Switch.

Number of power supplies required = 3+1 = 4

NOTE: If dual power feed redundancy (input power is from two separate high–linesources) is required, then the required power configuration is N+N. In this case, thenumber of power supplies needed for a fully loaded switch configuration is 6 (3+3).

To calculate the number of power supplies required for a fully loaded EX8208 switchconfiguration when input voltage is low line:

1. Compute the maximum internal power requirements for your switchconfiguration. See the maximum internal power consumption of a fully loadedswitch in “Power Consumption of Different EX8208 Switch Configurations” onpage 2.

Maximum internal power consumption of a fully loaded EX8208 switchconfiguration = 5678 W

4 ■ Number of Power Supples Required for Your EX8208 Switch Configuration



2. Divide the maximum internal power consumption by the output wattage of thepower supply. For low-line input voltage, the output wattage is 1200 W.

= (5678 W) / (1200 W)

Number of power supplies needed (N) = 5 (rounding up)

3. The required power configuration for EX8208 switches is N+1. See AC PowerSupply in an EX8200 Switch.

Number of power supplies required = 5+1= 6

NOTE: We recommend that you maintain N +1 power supplies in your switch at alltimes. Replace failed power supplies immediately to prevent unexpected failures.

If the number of power supplies installed in your switch is less than the number of power supplies required for N+1 redundancy, no line cards are powered on whenthe switch is booting up.

If a power supply fails or is removed without replacement such that the switch nolonger has the N+1 power redundancy configuration, a minor alarm is issued. If theproblem is not corrected within 5 minutes, a major alarm is issued. However, theswitch does not power off any line cards.

If a new line card is installed in an operational switch such that the total powerrequirement could exceed N+1 power redundancy, the switch does not power onthe new line card.

If more than one power supply fails or is removed without replacement such thatthe switch has fewer than N power supplies, the switch turns off power to all line

cards.

Related Topics ■ AC Power Supply in an EX8200 Switch

Published: 2009-07-15

Number of Power Supples Required for Your EX8208 Switch Configuration ■ 5

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Ac Power Ex8208 Requirements Calculating