Juniper EX8208 Hardware Manual page 125

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
The watt values shown in
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 60: Power Reserved for the Chassis
N+1 Configuration
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
page 120. Do not include the PoE power budgets for PoE line cards in this step. Use only the base power
requirements for all line cards.
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 watts + 8 (8–port SFP + line card watts)
= 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 watts + 8 (8–port SFP + line card watts)
= 1200 W + 8 (450) W
Table 60 on page 125 are the amount of power reserved by power management
Junos OS Release 10.1 or Earlier
1600 W
1600 W
"Power Requirements for EX8208 Switch Components" on
Table 60 on page 125.
Junos OS Release 10.2 or Later
1600 W
1200 W
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