Juniper Networks EX8208 - Manual (Page 144)

To calculate the number of power supplies required for your switch configuration:
1. Determine the power requirement of the base chassis (that is, the combined power
requirements of the fan tray, SRE module or modules, and the SF module) by
consulting Table 50 on page 118.
The watt values shown in Table 50 on page 118 are the amount of power reserved
by power management for the chassis in its power budget. It uses these values when
calculating used and available power and when determining whether sufficient
power exists to meet N, N+1, or N+N requirements.
Starting with Junos OS Release 10.2, when power management is configured for
N+N power redundancy, it reserves less power for the chassis so that more power
is available for line cards.
Table 50: Power Reserved for the Chassis
Junos OS Release 10.2 or
Later Junos OS Release 10.1 or
Earlier
1600 W 1600 W N+1 Configuration
1200 W 1600 W N+N Configuration
NOTE: The amount of power that power management reserves for the chassis is a set
value that does not vary depending on chassis components installed. The reserved
power is the same for base and redundant configurations and for switches that do not
have all base chassis components installed.
2. To the power reserved for the chassis, add the power requirements of the line cards.
For line card power requirements, refer to “Power Requirements for EX8208 Switch
Components” on page 111.
For example, for a switch fully loaded with 8-port SFP+ line cards and using N+1
power redundancy, the total power requirement:
= reserved chassis power + 8 (8–port SFP + line cards)
= 1600 W + 8 (450) W
= 1600 W + 3600 W
= 5200 W
For a switch fully loaded with 8-port SFP+ line cards, using N+N power redundancy,
and running Junos OS Release 10.2, the total power requirement:
= reserved chassis power + 8 (8–port SFP + line cards)
= 1200 W + 8 (450) W
= 1200 W + 3600 W
= 4800 W
Copyright © 2010, Juniper Networks, Inc. 118
Complete Hardware Guide for EX8208 Ethernet Switches