EX8208 Site Guidelines and Requirements

Environmental Requirements and Specifications for EX Series Switches

The switch must be installed in a rack or cabinet housed in a dry, clean, well-ventilated, and temperature-controlled environment.

• The site must be as dust-free as possible, because dust can clog air intake vents and filters, reducing the efficiency of the switch cooling system.

• Maintain ambient airflow for normal switch operation. If the airflow is blocked or restricted, or if the intake air is too warm, the switch might overheat, leading to the switch temperature monitor shutting down the switch to protect the hardware components.

Table 1 provides the required environmental conditions for normal switch operation.

General Site Guidelines

• Keep the area around the chassis free from dust and conductive material, such as metal flakes.

• Follow prescribed airflow guidelines to ensure that the cooling system functions properly and that exhaust from other equipment does not blow into the intake vents of the device.

• Follow the prescribed electrostatic discharge (ESD) prevention procedures to prevent damaging the equipment. Static discharge can cause components to fail completely or intermittently over time.

• Install the device in a secure area, so that only authorized personnel can access the device.

Site Electrical Wiring Guidelines

Table 2 describes the factors you must consider while planning the electrical wiring at your site.

Clearance Requirements for Airflow and Hardware Maintenance for an EX8208 Switch

When planning the site for installing an EX8208 switch, you must allow sufficient clearance around the switch.

• Allow at least 6 in. (15.2 cm) of clearance on each side of the chassis. For the cooling system to function properly, the airflow around the chassis must be unrestricted. See Figure 1.

  Figure 1: Airflow Through the EX8208 Switch Chassis

  

• If you are mounting the switch on a rack or cabinet along with other equipment, ensure that the exhaust from other equipment does not blow into the intake vents of the chassis.

• Leave at least 24 in. (61 cm) both in front of and behind the switch. Allow at least 6 in. (15.2 cm) of clearance on each side of the chassis. Leave adequate space at the front of the switch for service personnel to remove and install hardware components. NEBS GR-63 recommends that you allow at least 30 in. (76.2 cm) in front of the rack or cabinet and 24 in. (61 cm) behind the rack or cabinet. See Figure 2.

  Figure 2: Clearance Requirements for Airflow and Hardware Maintenance for an EX8208 Switch Chassis

  

Rack Requirements

You can mount the device on two-post racks or four-post racks.

Rack requirements consist of:

• Rack type

• Mounting bracket hole spacing

• Rack size and strength

• Rack connection to the building structure

Table 3 provides the rack requirements and specifications.

Cabinet Requirements

You can mount the device in a cabinet that contains a 19-in. rack.

Cabinet requirements consist of:

• Cabinet size

• Clearance requirements

• Cabinet airflow requirements

Table 4 provides the cabinet requirements and specifications.

Power Requirements for EX8208 Switch Components

Table 5 lists the power requirements for different hardware components of an EX8208 switch under typical voltage conditions.

Calculating Power Requirements for an EX8208 Switch

Use the information in this topic to calculate power consumption, system thermal output, and number of power supplies required for different EX8208 switch configurations.

Before you begin these calculations:

• Ensure you understand the different switch configurations. See EX8208 Switch Configurations.

• Ensure that you know the power requirements of different switch components. See Power Requirements for EX8208 Switch Components.

• If the switch contains PoE line cards, ensure that you understand the PoE power budget requirements of each line card. See Understanding PoE on EX Series Switches.

This topic describes these tasks.

• Calculating the Power Consumption of Your EX8208 Switch Configuration

• Calculating System Thermal Output for Your EX8208 Switch Configuration

• Calculating the Number of Power Supplies Required for Your EX8208 Switch Configuration

Calculating the Power Consumption of Your EX8208 Switch Configuration

1. Determine the maximum power consumption of the base chassis components (that is, the components other than the line cards):

   • Use Table 6 if your switch is configured for N+1 power redundancy or if your switch is configured for N+N power redundancy and is running Junos OS Release 10.1 or earlier.

   • Use Table 7 only if your switch is running Junos OS Release 10.2 or later and power management is configured for N+N power redundancy.

   Note

   In Junos OS Release 10.2 or later, if power management is configured for N+N redundancy, the maximum fan speed is lowered, reducing the chassis’ maximum power consumption.

   Table 6: Chassis Power Consumption for N+1 Configurations and for N+N Configurations Running Junos OS Release 10.1 or Earlier

   Chassis Component	Base Configuration	Redundant Configuration
   Fan tray	1100 W	1100 W
   Switch Fabric and Routing Engine (SRE) module	200 W	200 W
   Second SRE module	—	200 W
   Switch Fabric module	100 W	100 W
   Total	1400 W	1600 W

   Table 7: Chassis Power Consumption for N+N Configurations Running Junos OS Release 10.2 or Later

   Chassis Component	Base Configuration	Redundant Configuration
   Fan tray	700 W	700 W
   SRE module	200 W	200 W
   SRE module	—	200 W
   SF module	100 W	100 W
   Total	1000 W	1200 W

2. Calculate the maximum internal power consumption of the entire switch by adding in the power requirements of each line card.

   For example, for a switch fully loaded with 8-port SFP+ line cards and using N+1 power redundancy, the maximum internal power consumption:

   = (chassis watts) + 8 (8-port SFP+ line card watts)

   = (1600 W + 8 (450 W))

   = (1600 W + 3600 W)

   = 5200 W

   For switches with PoE line cards, be sure to include the configured PoE power budget for each line card.

3. Calculate the maximum system power consumption by dividing the maximum internal power consumption by the efficiency of the power supply. This accounts for the loss of energy within the power supply. Note

   The efficiency of a 2000 W AC power supply is approximately 90 percent when input is high-voltage line (200–240 VAC).

   The efficiency of a 2000 W AC power supply is approximately 87 percent when input is low-voltage line (100–120 VAC).

   For example, for a switch fully loaded with 8-port SFP+ line cards and using N+1 power redundancy with high-voltage line input, the maximum system power consumption:

   = (maximum internal power consumption) / (power supply efficiency)

   = (5200 W) / (0.90)

   = 5778 W

Calculating System Thermal Output for Your EX8208 Switch Configuration

Use the following procedure to calculate the system thermal output in British thermal units (BTU) per hour for your switch configuration.

1. Determine the maximum system power consumption of your switch in watts. See Calculating the Power Consumption of Your EX8208 Switch Configuration for how to do so.
2. Multiply the maximum system power consumption by 3.41.

   For example, for a switch fully loaded with 8-port SFP+ line cards and using N+1 power redundancy with high-voltage line input, the system thermal output:

   = (maximum system power consumption) x (3.41)

   = (5778 W) x (3.41) =

   = 19,703 BTU/hr

Calculating the Number of Power Supplies Required for Your EX8208 Switch Configuration

Use this procedure to calculate the number of power supplies required by your switch configuration. The required power configuration for EX8208 switches is N+1. You can optionally configure your switch for N+N configuration. For example, you might want dual power feed redundancy with AC power supplies, which requires an N+N configuration.

1. Determine the power requirement of the base chassis (that is, the combined power requirements of the fan tray, SRE module or modules, and the SF module) by consulting Table 8.

   The watt values shown in Table 8 are the amount of power reserved by power management for the chassis in its power budget. It uses these values when calculating used and available power and when determining whether sufficient power exists to meet N, N+1, or N+N requirements.

   Starting with Junos OS Release 10.2, when power management is configured for N+N power redundancy, it reserves less power for the chassis so that more power is available for line cards.

   Table 8: Power Reserved for the Chassis

   	Junos OS Release 10.1 or Earlier	Junos OS Release 10.2 or Later
   N+1 Configuration	1600 W	1600 W
   N+N Configuration	1600 W	1200 W

   Note

   The amount of power that power management reserves for the chassis is a set value that does not vary depending on chassis components installed. The reserved power is the same for base and redundant configurations and for switches that do not have all base chassis components installed.

2. To the power reserved for the chassis, add the power requirements of the line cards.

   For line card power requirements, refer to Power Requirements for EX8208 Switch Components. Do not include the PoE power budgets for PoE line cards in this step. Use only the base power requirements for all line cards.

   For example, for a switch fully loaded with 8-port SFP+ line cards and using N+1 power redundancy, the total power requirement:

   = reserved chassis watts + 8 (8–port SFP + line card watts)

   = 1600 W + 8 (450) W

   = 1600 W + 3600 W

   = 5200 W

   For a switch fully loaded with 8-port SFP+ line cards, using N+N power redundancy, and running Junos OS Release 10.2, the total power requirement:

   = reserved chassis watts + 8 (8–port SFP + line card watts)

   = 1200 W + 8 (450) W

   = 1200 W + 3600 W

   = 4800 W

3. Calculate the number of power supplies (N) required to meet the total power requirement by dividing the total power requirement by the output wattage of one power supply and then rounding up. Note

   If the input is high-voltage line (200–220 VAC), the output wattage of a 2000 W AC power supply is 2000 W.

   If the input is low-voltage line (100–120 VAC), the output wattage of a 2000 W AC power supply is 1200 W.

   For example, for a switch fully loaded with 8-port SFP+ line cards and using N+1 power redundancy with high-voltage line input , the required power supplies (N):

   = (total power requirement) / (output wattage of power supply)

   = (5200 W) / (2000 W)

   = 2.6

   = 3 (rounded up)

   For a switch fully loaded with 8-port SFP+ line cards, using N+N power redundancy with high-voltage line input, and running Junos OS Release 10.2, the required power supplies (N):

   = (total power requirement) / (output wattage of power supply)

   = (4800 W) / (2000 W)

   = 2.4

   = 3 (rounded up)

4. Add the number of power supplies needed to achieve the required power redundancy:

   • To achieve N+1 power redundancy, add a single power supply.

     For example, for a switch fully loaded with 8-port SFP+ line cards and using high-voltage line input, the total number of power supplies:

     = N + 1

     = 3 + 1

     = 4

   • To achieve N+N power redundancy, add N power supplies.

     For example, for a switch fully loaded with 8-port SFP+ line cards and using high-voltage line input, the total number of power supplies:

     = N + N

     = 3 + 3

     = 6

5. If the switch has PoE line cards:
   1. Add the configured PoE power budgets for PoE line cards to the total power requirement value that you calculated in step 2.
   2. Calculate the number of power supplies needed to meet the new total power requirement by dividing the total power requirement by the output wattage of one power supply and then rounding up.
   3. Compare this result to the N+1 or N+N value you calculated in step 4. Use the greater of the two values to determine how many power supplies you require.