Determining DC Power Requirements for Your MX2020 Router
This topic describes the MX2020 DC power subsystem, power zones, and DC 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 Power Subsystem Electrical Specifications).
MX 2020 DC Power Subsystem Components
The MX2020 DC power system is comprised of two subsystems. Each subsystem provides power to:
10 linecard slots
Nine DC Power Supply Modules (PSMs)
Two DC Power Distribution Modules (PDMs)
20 Modular Port Concentrators (MPCs) (10 MPCs per zone)
Two fan trays
Eight Switch Fabric Boards (SFBs)
Two Control Board and Routing Engines (CBREs)
Understanding Power Zones in the MX2020 DC Power Subsystem
The MX2020 DC power subsystem has two power zones: zone 0 and zone 1. Some FRUs draw power only from zone 0, some FRUs draw power only from zone 1, and some FRUs draw power from both zone 0 and zone 1. When calculating power requirements, ensure there is adequate power for each zone. Each zone needs to provide 70% of the total power required by shared FRUs. This means 140% of the power required by the FRUs is available in the two power zones combined.
There are two types of DC power subsystems available for the MX2020: a “base” DC power subsystem (MX2020BASEDC) and an “optimized” or premium DC power subsystem (MX2020PREMIUM2DC). The fan trays in an optimized DC power subsystem draw power from the power zones differently than the fan trays in a base DC power subsystem. In a base DC power subsystem, two of the four fan trays draw power from both zones. In the optimized DC power subsystem, two of the fan trays draw power from only one zone. Because of this, the optimized power subsystem requires less power. Since the two fantrays share power in a zone, they only require 100% of the power they are rated at (not 140%). This is a net savings of 40% * 1700W/fantray * 2 for the system and half that amount per power zone.
70% of the total power from zone 0 + zone 1 must be provided by EACH zone in the calculation.
Four DC Power Supply Modules (PSMs) per zone are mandatory for the MX2020 router with DC Power Distribution Modules (PDMs).
As illustrated in Figure 1 and described in Table 1, the power zones in the MX2020 DC base power subsystem distribute power to FRUs as follows:
Zone 0 powers only line card slots 09, and fan tray 1
Zone 1 powers only line card slots 1019, and fan tray 3
Zone 0 + Zone 1 (both zones provide power) to CBRE slot 0 and CBRE slot 1, fabric card slots 07, and fan tray 0 and 2
Table 1: MX2020 DC Power Zoning (Base DC Power Implementations)
Chassis Power Configuration  Power Zone  Power Distribution Module (PDM)  Power Supply Module (PSM)  Components Receiving Power 

DC power to lower half of MX2020 components  Lower (zone 0)  PDM 0 and 1  PSM slots 0 through 8 

DC power to upper half of MX2020 components  Upper (zone 1)  PDM 2 and 3  PSM slots 9 through 17 

Zone 0 + Zone 1 

As illustrated in Figure 2 and described in Table 2, the power zones in MX2020 DC optimized power subsystems distribute power to FRUs as follows:
Zone 0 powers only line card slots 17, and fan trays 0 and 1
Zone 1 powers only line card slots 1016, and fan trays 2 and 3
Zone 0 and Zone 1 (both zones provide power) to CBRE slot 0 and CBRE slot 1, and fabric card slots 07
Table 2: MX2020 DC Power Zoning (Optimized DC Power Implementations)
Chassis Power Configuration  Power Zone  Power Distribution Module (PDM)  Power Supply Module (PSM)  Components Receiving Power 

DC power to lower half of MX2020 components  Lower (zone 0)  PDM 0 and 1  PSM slots 1 through 7 

DC power to upper half of MX2020 components  Upper (zone 1)  PDM 2 and 3  PSM slots 10 through 16 

Zone 0 + Zone 1 

Calculating the DC Power Requirements for Your MX2020 Router
Follow these steps to calculate the DC power requirements for your MX2020 Router configuration.
 Calculate the total output power required for your MX2020
FRUs.Table 3 shows
the typical power usage for the MX2020 DC power subsystem FRUs.
Table 3: Typical DC Power Usage for MX2020 Router
Component
Model Number
Power Requirement (Watts) with 91% Efficiency
Base chassis
CHASBPMX2020
Fan trays (upper and lower)
MX2000FANTRAY
1700 W * 4 = 6800 W
MPC
MPC3D16XGESFPP
440 W * 20 = 8800 W
ADC
ADC
150 W * 20 = 3000 W
CBRE
REMX20001800X4
250 W * 2 = 500 W
SFB—slots 0 through 7
MX2000SFB
220 W * 8 = 1760 W
MX2020 DC power subsystem (upper and lower half of chassis, 60 A feeds to each PDM input)
MX2020 DC power subsystem (upper and lower half of chassis, 80 A feeds to each PDM input)
2100 W * 8 PSMs=16,800 W (+ 1 PSM@2100 W redundant capacity)
2500 W * 8 PSMs=20,000 W (+ 1 PSM@2500 W redundant capacity)
MX2020 DC power subsystem (upper and lower half of chassis, 240V feeds to each PDM input)
2500 W * 8 PSMs=20,000 W (+ 1 PSM@2500 W redundant capacity)
Note The power reservation for the critical FRUs is 7360 W. With power droopsharing 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.
 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 4 lists the MX2020 PSMs,
their maximum output power, and unused power (or power deficit).
Table 4: MX2020 PSM DC Output Power Budget
Power Supply Module
Maximum Output Power of Power Supply Module (Watt)
Maximum Output Power for System (Watt)—including redundant capacity
MX2020 DC PSM 60 A (feed to each input)
2100
37,800
MX2020 DC PSM 80 A or DC PSM (240 V China) (feed to each input)
2500
45,000
 Calculate input power. Divide the total output requirement
by the efficiency of the PSM. Refer to Table 5.
Table 5: Calculating DC Input Power
Power Supply Module
Power Supply Module Efficiency
Output Power Requirement (Watt)—per PSM
Input Power Requirement (Watt)—per PSM
MX2020 DC PSM 60 A
91%
2100
2307
MX2020 DC PSM 80 A or DC PSM (240 V China)
91%
2500
2747
 Calculate thermal output (BTUs) for cooling requirements.
Multiply the input power requirement (in watts) by 3.41. Refer to Table 6.
Table 6: Calculating DC Thermal Output (BTUs)
Power Distribution Module
Thermal Output (BTUs per hour)
MX2020 DC PDM
34.5 KW divided by 0.91 * 3.41 = 129,280 BTU/hr (Zone 0 output. The calculation method for Zone 1 is the same as for Zone 0).
34.5 KW of output power consumed by the chassis. This is the maximum output the chassis can consume in a redundant configuration. The input power is 34.5 divided by 0.91 = 37.9 KW.