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    Calculating Power Requirements for MX480 Routers

    The information in this topic helps you determine which power supplies are suitable for various configurations, as well as which power supplies are not suitable because output power is exceeded. You determine suitability by subtracting the total power draw from the maximum output of the power supplies. Afterward, the required input power is calculated. Finally, you calculate the thermal output. A sample configuration is provided in Table 2.

    We recommend that you provision power according to the maximum input current listed in the power supply electrical specifications (see AC Electrical Specifications for the MX480 Routerand DC Power Supply Electrical Specifications for the MX480 Router).

    Use the following procedures to calculate the power requirement:

    1. Calculate the power requirement.
    2. Evaluate the power budget.
    3. Calculate input power.
    4. Calculate thermal output (BTUs) for cooling requirements.

    Both normal-capacity and high-capacity MX480 chassis with DC power supplies are zoned, meaning that certain components are powered by specific power supplies (see Table 1 for information on zoning). When calculating power requirements, be sure that there is adequate power for each zone.

    For an AC-powered chassis, there is one overall zone. Two AC power supplies are mandatory for high-line, and three AC power supplies are mandatory for low-line power.

    Table 1: MX480 DC Zoning

    Zone

    Power Supply (PEM)

    Components Receiving Power

    Zone 0

    PEM 0 or 2

    • Fan Tray
    • DPC/MPC slots 0 and 1
    • SCB slots 0 and 1

    Zone 1

    PEM 1 or 3

    • Fan Tray
    • DPC slots 2 through 5

    The following sample configuration shows a DC-powered MX480 with:

    • Two 16-port 10-Gigabit Ethernet MPCs with SFP+(slots 0 and 1)
    • Two SCBs with two (redundant) RE-1800x2 routing engines (SCB slot 0 and SCB slot 1)
    • One DPCE-R-4XGE-XFP (slot 3)
    • High-capacity cooling system

      Note: The high-capacity cooling system satisfies cooling requirements of MPCs, and must be used for proper cooling.

    1. Calculate the power requirements (usage) using the values in Power Requirements for an MX480 Router as shown in Table 2.

      Table 2: Sample Power Requirements for an MX480 Router

      Chassis Component

      Part Number

      Power Requirement

      Zone

      Base system

      MX480BASE-DC-HIGH

      40 W

      Zone 0 and Zone 1

      High-capacity cooling system

      FFANTRAY-MX480-HC

      160 W

      Zone 0 and Zone 1

      MPC - Slot 2

      MPC-3D-16XGE-SFPP-R-B

      440 W

      Zone 1

      MPC - Slot 1

      MPC-3D-16XGE-SFPP-R-B

      440 W

      Zone 0

      SCB 1

      SCBE2-MX with

      RE-S-1800X2-8G

      185 W

      90 W

      Zone 0

      SCB 0

      SCBE2 with

      RE-S-1800X2-8G

      185 W

      90 W

      Zone 0

      DPC - Slot 3

      DPCE-R-4XGE-XFP

      310 W

      Zone 1

      Zone 0 total output power

      Zone 1 total output power

      1090 W

      850 W

      Zone 0 total output power (excluding cooling system)

      Zone 1 total output power (excluding cooling system)

      1010 W

      770 W

    2. Evaluate the power budget. In the case of a DC-powered chassis, evaluate the budget for each zone. In this step, we check the required power against the maximum output power of available power supply options.

      Note: The power for the cooling system comes from a different tap on the power supply, reserved for the cooling system only. The cooling system power requirement does not need to be deducted from the output power budget of the power supply.


      Table 3 lists the power supplies, their maximum output power, and unused power (or a power deficit) for MX480 AC chassis.Table 4 lists the power supplies, their maximum output power, and unused power (or a power deficit) for MX480 DC chassis. See AC Electrical Specifications for the MX480 Router and DC Power Supply Electrical Specifications for the MX480 Router for more information about the MX480 power supply electrical specifications.

      Table 3: Calculating Power Budget for a MX480 AC Chassis

      Power Supply

      Maximum System Output Power

      Unused Power1

      MX480 AC Normal-capacity (low-line)

      3081 W

      2071 W

      MX480 AC Normal-capacity (high-line)

      3200 W

      2190 W

      MX480 AC High-capacity (low-line)

      3501 W

      2491 W

      MX480 AC High-capacity (high-line)

      4100 W

      3090 W

      1 For this configuration, output power excluding the cooling system is 1360 W.

      Table 4: Calculating Power Budget for a MX480 DC Chassis

      Power Supply

      Maximum System Output Power

      Zone 0 Unused Power1

      Zone 1 Unused Power2

      MX480 DC Normal-capacity

      3200 W

      2190 W

      2430 W

      MX480 DC High-capacity (DIP=0)

      Note: The DIP switch position is expected input current; the correct feeds must be present to obtain the desired output power.

      4800 W

      3790 W

      4030 W

      MX480 DC High-capacity (DIP=1)

      Note: The DIP switch position is expected input current; the correct feeds must be present to obtain the desired output power.

      5200 W

      4190W

      4430W

      1 For this configuration, output power excluding the cooling system is 1010 W.

      2 For this configuration, output power excluding the cooling system is 770 W.

    3. Calculate input power. In this step, the input power requirements for the example configuration are calculated. To do this, divide the total output requirement by the efficiency of the power supply as shown in Table 5.

      Table 5: Calculating Input Power Examples

      Power Supply

      Power Supply Efficiency1

      Input Power Requirement2

      MX480 AC Normal-capacity (high-line)

      85 %

      1282 W

      MX480 AC High-capacity (high-line)

      89 %

      1225 W

      MX480 DC Normal-capacity

      ~98 %

      1112 W3

      MX480 DC High-capacity

      ~98 %

      1112 W3

      1 These values are at full load and nominal voltage.

      2 For this configuration, total power is 1090 W.

      3 Zone 0 requirement.

    4. Calculate thermal output (BTUs). To calculate this, multiply the input power requirement (in watts) by 3.41.

      Table 6: Calculating Thermal Output

      Power Supply

      Thermal Output (BTUs per hour)

      MX480 AC Normal-capacity (high-line)

      1282 * 3.41 = 4372 BTU/hr

      MX480 AC High-capacity (high-line)

      1225 * 3.41 = 4177 BTU/hr

      MX480 DC Normal-capacity

      1112 * 3.41 = 3792 BTU/hr1

      MX480 DC High-capacity

      1112 * 3.41 = 3792 BTU/hr1

      1 Zone 0 output.

    Modified: 2016-03-28