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Cooling System and Airflow in an EX4400 Switch

The cooling system in an EX4400 switch consists of two fan modules for the chassis and a single built-in fan in each power supply. The airflow direction depends on the fan modules and power supplies installed in the switch. You can order an EX4400 switch that supports front-to-back (air enters through the front panel of the switch) or back-to-front airflow (air enters through the rear panel of the switch).

Fan Modules

The fan modules are hot-removable and hot-insertable field-replaceable units (FRUs) installed in the rear panel of the switch: You can remove and replace them without powering off the switch or disrupting switch functions.

We ship EX4400 switches with two fan modules (1+1 redundancy) preinstalled in the rear panel of the switch. The fan module slots are numbered 0 and 1, and each slot has a fan icon next to it.

The fan modules are available in two models that have different airflow directions:

  • Front-to-back (cold air enters through the vents on the front panel of the switch and hot air exhausts through the vents on the rear panel), indicated by the AIR OUT label and the Juniper Gold handle.

  • Back-to-front (cold air enters through the vents on the rear panel of the switch and hot air exhausts through the vents on the front panel), indicated by the AIR IN label and the Juniper Azure Blue handle.

Figure 1 shows the fan module used in an EX4400 switch.

Figure 1: Fan Module Used in an EX4400 Switch Air outlet module with fan icon and "AIR OUT" label, featuring hexagonal mesh and mounting features for ventilation system installation.
Note:

You must install all the fan modules and they must be operational for optimal functioning of the switch.

Leave at least 4 in. (10.16 cm) clearance in front and 2 in. (5.08 cm) behind the chassis for airflow.

If the switch is operational while you are replacing fan modules, you must remove only one fan module at a time. The switch continues to operate for 60 seconds without thermal shutdown while you are replacing a fan module.

CAUTION:

Do not mix:

  • Fan modules with different airflow directions in the same chassis.

  • Power supplies with different airflow directions in the same chassis.

  • Power supplies and fan modules with different airflow directions in the same chassis.

If you install power supplies or fan modules with different airflow directions, Junos OS raises an alarm.

Under normal operating conditions, the fan modules operate at a moderate speed. Temperature sensors in the chassis monitor the temperature within the chassis.

If a fan module fails or if the ambient temperature inside the chassis rises above the acceptable range, Junos OS raises an alarm. If the temperature inside the chassis rises above the threshold temperature, the system shuts down automatically.

EX4400 Switches with Front-to-Back Airflow

In the EX4400 switch models that have front-to-back airflow, cold air enters the chassis through the vents on the front panel and hot air exhausts the chassis through the vents on the rear panel.

  • Figure 2 shows the front-to-back airflow through an EX4400-24T switch.

  • Figure 3 shows the front-to-back airflow through an EX4400-24P switch.

  • Figure 4 shows the front-to-back airflow through an EX4400-24MP switch.

  • Figure 5 shows the front-to-back airflow through an EX4400-24X switch.

  • Figure 6 shows the front-to-back airflow through an EX4400-48T switch.

  • Figure 7 shows the front-to-back airflow through an EX4400-48P switch.

  • Figure 8 shows the front-to-back airflow through an EX4400-48XP switch.

  • Figure 9 shows the front-to-back airflow through an EX4400-48MP switch.

  • Figure 11 shows the front-to-back airflow through an EX4400-48F switch.

  • Figure 10 shows the front-to-back airflow through an EX4400-48MXP switch.

Figure 2: Front-to-Back Airflow Through an EX4400-24T Switch Chassis Diagram showing airflow in a server chassis with green arrows indicating cooling from front to rear.
Figure 3: Front-to-Back Airflow Through an EX4400-24P Switch Chassis Diagram showing airflow in a server chassis with green arrows from front intake to rear exhaust for cooling components.
Figure 4: Front-to-Back Airflow Through an EX4400-24MP Switch Chassis Diagram showing airflow in a server chassis with green arrows moving from front to rear for cooling components.
Figure 5: Front-to-Back Airflow Through an EX4400-24X Switch Chassis Diagram of server chassis with green arrows showing airflow from front to rear for cooling; includes components and slots.
Figure 6: Front-to-Back Airflow Through an EX4400-48T Switch Chassis Diagram showing airflow in a server chassis with green arrows indicating air enters from the front and exits through the rear for cooling.
Figure 7: Front-to-Back Airflow Through an EX4400-48P Switch Chassis Diagram showing server chassis airflow with green arrows indicating air entering through the front and exiting through the rear panel.
Figure 8: Front-to-Back Airflow Through an EX4400-48XP Switch Chassis Diagram showing server chassis airflow with green arrows indicating air entering through the front and exiting through the rear panel.
Figure 9: Front-to-Back Airflow Through an EX4400-48MP Switch Chassis Diagram showing airflow in a server chassis with green arrows indicating air moving from front to rear for cooling.
Figure 10: Front-to-Back Airflow Through an EX4400-48MXP Switch Chassis Diagram showing airflow in a server chassis with green arrows indicating air moving from front to rear for cooling.
Figure 11: Front-to-Back Airflow Through an EX4400-48F Switch Chassis Diagram of airflow in a server chassis with green arrows showing air moving from front to rear for cooling.

Mixing components with different airflow directions in the same chassis hampers the performance of the cooling system of the switch and leads to overheating of the chassis.

EX4400 Switches with Back-to-Front Airflow

In the EX4400 switch models that have back-to-front airflow, cold air enters the chassis through the vents on the rear panel of the switch and hot air exhausts the chassis through the vents on the front panel.

  • Figure 12 shows the back-to-front airflow through an EX4400-24T switch.

  • Figure 13 shows the back-to-front airflow through an EX4400-24X switch.

  • Figure 14 shows the back-to-front airflow through an EX4400-48T switch.

  • Figure 15 shows the back-to-front airflow through an EX4400-48F switch.

Figure 12: Back-to-Front Airflow Through an EX4400-24T Switch Chassis Diagram of a server chassis layout showing airflow direction with green arrows from front panel on left to rear panel on right for cooling.
Figure 13: Back-to-Front Airflow Through an EX4400-24X Switch Chassis Diagram of airflow in server chassis with green arrows showing intake at front and exhaust at rear for cooling components.
Figure 14: Back-to-Front Airflow Through an EX4400-48T Switch Chassis Diagram of airflow in a computer chassis with green arrows showing air movement from front to rear for component cooling.
Figure 15: Back-to-Front Airflow Through an EX4400-48F Switch Chassis Airflow diagram in computer chassis with green arrows showing airflow from front to rear, illustrating cooling mechanisms.

Mixing components with different airflow directions in the same chassis hampers the performance of the cooling system of the switch and leads to overheating of the chassis.

How to Position the Switch

Position the switch with front-to-back airflow in such a manner that the AIR OUT labels on the fan modules and power supplies are next to the hot aisle (see Figure 16).

Figure 16: Deployment of Switches with Front-to-Back Airflow Through the Switch Chassis Deployment of Switches with Front-to-Back Airflow Through the Switch Chassis

Position the switch with back-to-front airflow in such a manner that the AIR IN labels on the fan modules and power supplies are next to the cold aisle (see Figure 17).

Figure 17: Deployment of Switches with Back-to-Front Airflow Through the Switch Chassis Deployment of Switches with Back-to-Front Airflow Through the Switch Chassis

Fan Module Status

Each fan module has a status LED on it that indicates the status of the fan module (see Figure 18).

Figure 18: Fan Module LED Rear view of a network device with console and management ports, reset and USB port, cooling fans labeled AIR OUT, power input, and empty expansion slots.

Table 1 describes the LED.

Table 1: Fan Module Status LED

State

Description

Lit green

The fan module is functioning normally.

Unlit

Indicates one of the following:

  • The fan module is not installed properly.

  • The fan module is not functioning normally.

  • The airflow direction of the fan module does not match with the airflow direction of the other components installed in the switch.