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; MX960 chassis with high-capacity AC power supplies; MX960 high-capacity second-generation AC power supplies; and MX960 high-voltage second-generation universal 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.

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	FANTRAY-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).

   Note:

   The following power consumption figures are representational and may have round-off errors. Refer the Power Calculator tool for exact power requirements.

   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)	3400 W (one feed)	–	Power exceeded	Power exceeded
   	4100 W (two feeds)	8200 W (two feeds)		1165 W	875 W
   MX960 DC normal-capacity	2800 W	5600 W	–	Power exceeded	Power exceeded
   MX960 AC high-capacity second-generation	2300 W (one feed)	4230 W (one feed)		Power exceeded	Power exceeded
   	5100 W (two feeds)	10200 W (two feeds)		2165 W	1875 W
   MX960 high-voltage second-generation (HVAC or HVDC)	5100 W	10200 W		Power exceeded
   MX960 DC high-capacity	1700 W (one feed)	3400 W (one feed)	–	Power exceeded	Power exceeded
   	4100 W (two feeds)	8200 W (two feeds)		1165 W	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
   MX960 AC high-capacity second-generation	91 %	3225 W
   MX960 (HVAC or HVDC) high-voltage second-generation universal	91 %	3225 W

   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
   MX960 AC high-capacity second-generation	3225 * 3.41 = 10997 BTU/hr1
   MX960 (HVAC or HVDC) high-voltage second-generation universal	3225 * 3.41 = 10997 BTU/hr1

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