Juniper Networks EX8208 manual Copyright 2010, Juniper Networks, Inc 119

Chapter 7: Planning Power Requirements

3.Calculate the number of power supplies (N) required to meet the total power requirement by dividing the total power requirement by the output wattage of one power supply and then rounding up.

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

If the input is low-voltage line (100–120 VAC), the output wattage of a 2000 W AC power supply is 1200 W.

For example, for a switch fully loaded with 8-port SFP+ line cards and using N+1 power redundancy with high-voltage line input , the required power supplies (N):

=(total power requirement) / (output wattage of power supply)

=(5200 W) / (2000 W)

=2.6

=3 (rounded up)

For a switch fully loaded with 8-port SFP+ line cards, using N+N power redundancy with high-voltage line input, and running Junos OS Release 10.2, the required power supplies (N):

=(total power requirement) / (output wattage of power supply)

=(4800 W) / (2000 W)

=2.4

=3 (rounded up)

4.Add the number of power supplies needed to achieve the required power redundancy:

• To achieve N+1 power redundancy, add a single power supply.

For example, for a switch fully loaded with 8-port SFP+ line cards and using high-voltage line input, the total number of power supplies:

=N + 1

=3 + 1

=4

•To achieve N+N power redundancy, add N power supplies.

For example, for a switch fully loaded with 8-port SFP+ line cards and using high-voltage line input, the total number of power supplies:

=N + N

=3 + 3

=6

Copyright © 2010, Juniper Networks, Inc. 119