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Determining High-Voltage Universal Power Requirements for Your MX2020 Router

This topic describes the MX2020 HVAC/HVDC power subsystem, power zones, and power usage to help you determine which Power Supply Modules (PSMs) are suitable for your router configuration.

We recommend that you provision power according to the maximum input current listed in the power subsystem electrical specifications (see MX2000 Router DC (-48 V) Power Subsystem Electrical Specifications).

MX 2020 Power Subsystem Components

The MX2020 HVAC/HVDC power system is comprised of two subsystems. Each subsystem provides power to:

  • 10 line-card slots, housing 10 Modular Port Concentrators (MPCs)

  • Nine Universal (HVAC/HVDC) Power Supply Modules (PSMs)

  • Two Universal (HVAC/HVDC) Power Distribution Modules (PDMs)

  • Two fan trays

  • Eight Switch Fabric Boards (SFBs)

  • Two Control Board and Routing Engines (CB-REs)

Calculating the HVAC/HVDC Power Requirements for Your MX2020 Router

Follow these steps to calculate the HVAC/HVDC power requirements for your MX2020 Router configuration.

  1. Calculate the total output power required for your MX2020 FRUs. Table 1 shows the maximum power usage for the MX2020 HVAC/HVDC power subsystem FRUs.

    Table 1: HVAC/HVDC Power Usage for MX2020 Router


    Model Number

    Power Requirement (Watts) with 91% Efficiency

    Base chassis



    Fan trays (upper and lower)


    1500 W * 4 = 6000 W



    1980 W * 20 = 39600 W



    150 W * 18 = 3000 W



    250 W * 2 = 500 W

    SFB—slots 0 through 7


    540 W * 8 = 4320 W

    MX2020 HVAC/HVDC power subsystem (upper and lower half of chassis, 19 A feeds to each PDM input)

    3000 W * 8 PSMs=24,000 W (+ 1 PSM@3000 W redundant capacity)


    The power reservation for the critical FRUs is 7360 W. With power droop-sharing between the two zones, the power reservation for critical FRUs is reduced to 5662 W. This number assumes a 70/30% load on the power zones when droop sharing is enabled.

  2. Evaluate the power budget, including the budget for each configuration if applicable, and check the required power against the maximum output power of available PSM options. Table 2 lists the MX2020 PSMs, their maximum output power, and unused power (or power deficit).

    Table 2: MX2020 PSM Output Power Budget

    Power Supply Module

    Maximum Output Power of Power Supply Module (Watt)

    Maximum Output Power for System (Watt)—including redundant capacity

    MX2020 Universal (HVAC/HVDC) PSM

    3000 W for single feed

    3400 W for dual feed

    3000 * 18 PSM with single feed = 54,000 W (PSM redundancy)

    3400 * 17 PSM with dual feed = 57,800 W (feed redundancy)

  3. Calculate input power. Divide the total output requirement by the efficiency of the PSM. Refer to Table 3.

    Table 3: Calculating Input Power

    Power Supply Module

    Power Supply Module Efficiency

    Input Power Requirement (Watt)—per PSM

    MX2020 Universal (HVAC/HVDC) PSM


    3300 W for single feed, 3800 W for dual feed

  4. Calculate thermal output (BTUs) for cooling requirements. Multiply the input power requirement (in watts) by 3.41. Refer to Table 4.

    Table 4: Calculating Typical Thermal Output (BTUs)

    Loaded Chassis Heat Load

    Typical Thermal Output (BTUs per hour)

    Loaded chassis configuration

    (Typical power divided by 0.91) * 3.41 = BTU/hr.

    (BTU = 36,274 divided by 0.91) * 3.41 = 11,690 BTU/hr.

    36,274 KW of output power consumed by the chassis. This is the typical output the chassis can consume in a redundant configuration.