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    Cooling System and Airflow in an EX4500 Switch

    The cooling system in an EX4500 switch consists of a single fan tray. The fan tray is a hot-insertable and hot-removable field-replaceable unit (FRU). The fan tray contains five fans (see Figure 1).

    Figure 1: Fan Tray Used in an EX4500 Switch

    Fan Tray Used in an EX4500 Switch

    The fan tray installs horizontally in the rear of the chassis. The fan tray has two handles, one on each side that facilitate handling of the fan tray.

    You remove and replace the fan tray from the rear of the chassis. The switch continues to operate for a limited time (30 seconds) during the replacement of the fan tray without thermal shutdown.

    The fan tray provides front-to-back or back-to-front airflow depending on the switch model you purchase. Table 1 shows the different EX4500 switch models and their direction of airflow.

    Note: The side of the switch where the network ports are located is the front of the switch.

    Table 1: Airfow Direction in EX4500 Switch Models

    Model

    Direction of Airflow

    EX4500-40F-FB

    Front-to-back

    EX4500-40F-BF

    Back-to-front

    EX4500-40F-FB- C

    Front-to-back

    EX4500-40F-BF-C

    Back-to-front

    EX4500-40F-DC-C

    Front-to-back

    EX4500-40F-VC1-FB

    Front-to-back

    EX4500-40F-VC1-BF

    Back-to-front

    EX4500-40F-VC1-DC

    Front-to-back

    In the EX4500 switch models that have front-to-back airflow, the air intake to cool the chassis is located on the front of the chassis. Air is pulled into the chassis and pushed toward the fan tray. Hot air exhausts from the rear of the chassis. See Figure 2.

    Figure 2: Front-to-Back Airflow Through the EX4500 Switch Chassis

    Front-to-Back Airflow Through
the EX4500 Switch Chassis

    In the EX4500 switch models that have back-to-front airflow, the air intake to cool the chassis is located on the rear of the chassis. Air is pulled into the chassis and pushed away from the fan tray. Hot air exhausts from the front of the chassis. See Figure 3.

    Figure 3: Back-to-Front Airflow Through the EX4500 Switch Chassis

    Back-to-Front Airflow Through
the EX4500 Switch Chassis

    Each fan tray has colored intake or exhaust labels that are visible through the fan tray vents. The INTAKE label is orange. The EXHAUST label is green.

    Note: Only one of the labels, INTAKE or EXHAUST, is visible through the vents of the installed fan tray.

    The color of the label visible through the vents of the installed fan tray must match the color of the ejector lever on the installed power supply. The color match indicates that the power supply has the correct airflow for this model. See AC Power Supply in EX4500 Switches.

    Caution: To prevent overheating of the chassis, verify that the color of the label visible through the vents of the installed fan tray matches the color of the ejector lever of the installed power supply. A color match indicates that the direction of airflow through the fan tray matches the direction of airflow of the power supply.

    Temperature sensors in the chassis monitor the temperature within the chassis. The fan tray used in the switch comes with load-sharing redundancy that can tolerate a single fan failure at room temperature (below 113° F/45° C) to still provide sufficient cooling.

    Under normal operating conditions, the fans in the fan tray run at less than full speed. If a fan fails or the ambient temperature rises above the threshold 113° F (45° C), the speed of the remaining fans is automatically adjusted to keep the temperature within the acceptable range, 32° F (0° C) through 113° F (45° C).

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

    You can check the status of fans and the chassis temperature from the Environment Status option in the Status menu on the LCD panel. See LCD Panel in EX4500 Switches.

    You cannot replace a single fan. If one or more fans fail, you must replace the entire fan tray.

    Published: 2013-01-30