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# Calculating Power Requirements for the SRX5400 Services Gateway

The information in this topic helps you determine which power supply configurations are suitable for various services gateway configurations, as well as which configurations 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.

We recommend that you provision power according to the maximum input current listed in the power supply electrical specifications (see SRX5400 Services Gateway AC Power Supply Specifications and SRX5400 Services Gateway DC Power Supply Specifications).

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.

The following sample configuration shows an SRX5400 Services Gateway chassis with various power supplies and:

• Two SRX5K-SPC-4-15-320 (SPC2) Services Processing Card (SPC) (slots 1 and 2)

• One SRX5K-MPC (IOC2) with two MICs installed in it (slot 1/0)

• One switch control board SRX5K-SCB (SCB1) or SRX5K-SCBE (SCB2) and one Routing Engine SRX5K-RE-13-20 (RE1) or SRX5K­RE-1800X4 (RE2) installed in it (SCB slot 0)

1. Calculate the power requirements (usage) as shown in Table 1.

Table 1: Sample Power Requirements for an SRX5400 Services Gateway

Chassis Component

Part Number

Power Requirement

Base system

SRX5400-CHAS

40 W

Fan tray

SRX5400-FAN

75 W

MPC - slot 1/0

IOC2

SRX-MIC-2X40-QSFP

SRX-QSFP-40G-SR4

570 W

SPC - slots 1 and 2

SCP2

585 W * 2 = 1170 W

SCB 0

SCB1 with

RE1

Or

150 W

90 W

SCB2 with

RE2

>150 W

90 W

Total power requirement

2095 W

Total power requirement excluding cooling system

2020 W

2. Evaluate the power budget. 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 2 lists the power supplies, their maximum output power, and unused power (or a power deficit) for an AC-powered services gateway. Table 3 lists the power supplies, their maximum output power, and unused power (or a power deficit) for a DC-powered services gateway.

Table 2: Calculating Power Budget, AC-Powered Chassis

Maximum Output Power of Power Supply

Maximum Output Power for System

Unused Power

1167 W (low-line)

1167W x 2 = 2334 W

(2+1 Redundancy)

2334 - 2095 = 239W

2050 W (high-line)

2050 x 2 = 4100 W

(2+1 Redundancy)

4100 - 2095 = 2005W

Table 3: Calculating Power Budget, DC Powered Chassis

Maximum Output Power of Power Supply

Maximum Output Power for System

Unused Power

2400 W (DIP=0)

2400 W

(1+1 Redundancy)

2400 - 2095 = 305 W

2600 W (DIP=1)

2600W

(1+1 Redundancy)

2600 - 2095 = 505 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 Here we include the power drawn by the cooling system.

Table 4: Calculating System Input Power

Power Supply

Power Supply Efficiency1

Input Power Requirement

SRX5400 AC

89 %

2095/0.89 = 2354 W

SRX5400 DC

~98 %

2095/0.98 = 2138 W

1 These values are at full load and nominal voltage.

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

Table 5: Calculating System Thermal Output

Power Supply

Thermal Output (BTUs per hour)

SRX5400 AC

2354 * 3.41 = 8027 BTU/hr

SRX5400 DC

2138 * 3.41 = 7291 BTU/hr

The following sample configuration shows an SRX5400 Services Gateway chassis with various power supplies and:

• Two SRX5K-SPC-4-15-320 (SPC2) Services Processing Card (SPC) (slots 1 and 2)

• One IOC3 (SRX5K-MPC3-40G10G or SRX5K-MPC3-100G10G) (slot 1/0)

• One switch control board SRX5K-SCB3 (SCB3) and one Routing Engine RE2 installed in SCB slot 0

1. Calculate the power requirements (usage) as shown in Table 6.

Table 6: Sample Power Requirements for an SRX5400 Services Gateway with SCB3, IOC3, and RE2

Chassis Component

Part Number

Power Requirement

Base system

SRX5400-CHAS

40 W

Fan tray

SRX5400-FAN

75 W

MPC - slot 1/0

IOC3

607 W

SPC - slots 1 and 2

SCP2

585 W * 2 = 1170 W

SCB 0

SCB3

RE2

300 W

90 W

Total power requirement

2282 W

Total power requirement excluding cooling system

2207 W

2. Evaluate the power budget. 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 7 lists the power supplies, their maximum output power, and unused power (or a power deficit) for an AC-powered services gateway. Table 8 lists the power supplies, their maximum output power, and unused power (or a power deficit) for an AC-powered services gateway.

Table 7: Calculating Power Budget, AC-Powered Chassis

Maximum Output Power of Power Supply

Maximum Output Power for System

Unused Power

1167 W (low-line)

1167 x 2 = 2334 W

(2+1 Redundancy)

2334 - 2282 = 52W

2050 W (high-line)

2050 x 2 = 4100 W

(2+1 Redundancy)

4100 - 2282 = 1818 W

Table 8: Calculating Power Budget, DC Powered Chassis

Maximum Output Power of Power Supply

Maximum Output Power for System

Unused Power

2400 W (DIP=0)

2400W

(1+1 Redundancy)

2400 - 2282 = 118W

2600 W (DIP=1)

2600W

(1+1 Redundancy)

2600 - 2282 = 318 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 9 Here we include the power drawn by the cooling system.

Table 9: Calculating System Input Power

Power Supply

Power Supply Efficiency1

Input Power Requirement

SRX5400 AC

89 %

2282/0.89 = 2564 W

SRX5400 DC

~98 %

2282/0.98 = 2329 W

1 These values are at full load and nominal voltage.

4. Calculate thermal output (BTUs) for the system. To calculate this value, multiply the total input power requirement (in watts) by 3.41 as shown in Table 10.

Table 10: Calculating System Thermal Output

Power Supply

Thermal Output (BTUs per hour)

SRX5400 AC

2564 * 3.41 = 8743 BTU/hr

SRX5400 DC

2329 * 3.41 = 7941 BTU/hr