Juniper MX10008, Hardware Manual

Page: 103 / 361

In the previous examples, we calculated that an MX10008 AC system would require 11800 W with
eight line cards. In this example, we calculate the total power available for this configuration:
= (14050 W) / (2700 W)
= 5.20
Round up the result to 6 AC power supplies.
3. Calculate how much power the power supplies need. To determine the power required, multiply the
number of power supplies by the power supply wattage and divide by the efficiency of the power
supply. The efficiency rate accounts for the loss of energy within the power supply and is 89 percent
for MX10008 power supplies.
For example if you have an AC system with four power supplies:
= 4 (2700 W) / (efficiency rating)
= (10800 W) / (0.89)
= 12135 W
Table 34 on page 104 shows how much power is required for various configurations.
Table 34: Total Power Required
DC AC Number of Power Supplies
8427 W 9102 W 3
11236 W 12135 W 4
14045 W 15169 W 5
16854 W 18204 W 6
NOTE: We recommend that you maintain six power supplies in your router at all times. Replace
failed power supplies immediately to prevent unexpected failures.
If a new line card is installed in an operational router, power management does not power on the
line card if the increased power demand exceeds the total available power, including redundant
power. If redundant power is used to power on the line card, a minor alarm is raised, which becomes
a major alarm in five minutes if the condition is not corrected.
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