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Calculating Power Requirements for MX960 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 current is calculated. Finally, you calculate the thermal output. A sample configuration is provided in Table 1.

We recommend that you provision power according to the maximum input current listed in the power supply electrical specifications (see Electrical Specifications for the MX960 AC Power Supply and Electrical Specifications for the MX960 DC Power Supply).

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 MX960 chassis with DC power supplies and MX960 chassis with high-capacity AC power supplies are zoned. MX960 chassis with normal-capacity AC power supplies have one overall zone. Zoning means 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.

Three AC power supplies are mandatory for MX960 chassis with normal-capacity AC power supplies.

Table 1: MX960 Zoning

Chassis Power Configuration

Zone

Power Supply (PEM)

Components Receiving Power

MX960 DC (normal-capacity and high-capacity power supplies); MX960 AC (high-capacity power supplies)

Zone 0

PEM 0 or 2

  • Lower fan tray

  • DPC/MPC slots 6 through 11

  • SCB slots 1 through 2

MX960 DC (normal-capacity and high-capacity power supplies); MX960 AC (high-capacity power supplies)

Zone 1

PEM 1 or 3

  • Upper fan tray

  • DPC/MPC slots 0 through 5

  • SCB slot 0

The following sample configuration shows an MX960 chassis with:

  • Four high-capacity AC power supplies (using two feeds for each power supply); two supplies are active, two are redundant

  • Six 16 port 10 GbE MPC with SFP+ interfaces (slots 0 through 5)

  • Two SCBs with two (redundant) RE-1800x2 routing engines (SCB slot 0 and SCB slot 1)

  • SCB (SCB slot 6)

  • Five 16 port 10 GbE MPC with SFP+ interfaces (slots 7 through 11)

  • High-capacity cooling system (upper and lower fan trays)

    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 MX960 Router as shown in Table 2.

    Table 2: Sample Power Requirements for an MX960 Router

    Chassis Component

    Part Number

    Power Requirement

    Zone

    Base system

    MX960BASE-AC-HIGH

    50 W1

    High-capacity cooling system

    FFANTRAY-MX960-HC

    320 W * 2 = 640 W

    Zone 0 (lower fan tray) and Zone 1 (upper fan tray)

    MPC - slots 0 through 5

    MPC-3D-16XGE-SFPP

    440 W * 6 = 2640 W

    Zone 1

    MPC - slots 7 through 11

    MPC-3D-16XGE-SFPP

    440 W * 5 = 2200 W

    Zone 0

    SCB 0

    SCBE2-MX with

    RE-S-1800X2-8G

    185 W

    90 W

    Zone 1

    SCB 1

    SCBE2-MX with

    RE-S-1800X2-8G

    185 W

    90 W

    Zone 0

    SCB 2 - slot 6

    SCBE2-MX

    185 W

    Zone 0

    MX960 normal-capacity AC (not zoned)

    Zone 0 total output power

    Zone 1 total output power

    6265 W

    3005 W

    3260 W

    1 Divided equally between zone 0 and zone 1.

  2. Evaluate the power budget, including the budget for each zone if applicable. In this step, we check the required power against the maximum output power of available power supply options.

    Table 3 lists the power supplies, their maximum output power, and unused power (or a power deficit).

    Table 3: Calculating Power Budget

    Power Supply

    Maximum Output Power of Power Supply

    Maximum Output Power for System

    Nonzoned Unused Power

    Zone 0 Unused Power1

    Zone 1 Unused Power2

    MX960 AC normal-capacity

    1700 W

    5100 W

    Power exceeded (non-zoned; 5100 W - 6160 = power exceeded)

    MX960 AC high-capacity

    1700 W (one feed)

    4100 W (two feeds)

    3400 W (one feed)

    8200 W (two feeds)

    Power exceeded

    1165 W

    Power exceeded

    875 W

    MX960 DC normal-capacity

    2800 W

    5600 W

    Power exceeded

    Power exceeded

    MX960 DC high-capacity

    1700 W (one feed)

    4100 W (two feeds)

    3400 W (one feed)

    8200 W (two feeds)

    Power exceeded

    1165 W

    Power exceeded

    875 W

    1 For this configuration, output power is 2935 W.

    2 For this configuration, output power is 3225 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 4.Note

    MX960 AC and MX960 DC normal-capacity power supplies are not included in the following table, because their power budget was exceeded in the sample configuration.

    Table 4: Calculating Input Power

    Power Supply

    Power Supply Efficiency1

    Input Power Requirement2

    MX960 AC high-capacity

    ~88 %

    3335 W3

    MX960 DC high-capacity

    86 %

    3413 W3

    1 These values are at full load and nominal voltage.

    2 For this configuration, total power for zone 0 is 2935 W. The calculation method for zone 1 is the same as zone 0.

    3 Zone 0 requirement.

  4. Calculate thermal output (BTUs). To calculate this, multiply the input power requirement (in watts) by 3.41 as shown in Table 5.

    Table 5: Calculating Thermal Output

    Power Supply

    Thermal Output (BTUs per hour)

    MX960 AC high-capacity

    3335 * 3.41 = 11,372 BTU/hr1

    MX960 DC high-capacity

    3413 * 3.41 = 11,638 BTU/hr1

    1 Zone 0 output. The calculation method for zone 1 is the same as for zone 0.