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Cooling System and Airflow in an OCX1100 Switches

 

The cooling system in an OCX1100-48SX switch consists of four fan modules and a single fan in each power supply. OCX1100 switches provide back-to-front airflow (air enters through the vents on the rear panel of the switch chassis), indicated by the label AIR IN (AFI), or front-to-back (air exhausts through the vents on the rear panel of the switch chassis), indicated by the label AIR OUT (AFO)—depending on the fan modules and power supplies installed in the switch.

Fan Modules

The OCX1100 switches fan modules are hot-insertable and hot-removable field-replaceable units (FRUs).

All OCX1100-48SX switches are shipped with four fan modules preinstalled in the rear panel of the switch. Each switch can accommodate four fan modules in the fan module slots on the rear panel of the switch. The fan module slots are numbered 0 through 3 and each slot has a fan icon next to it.

Figure 1 shows the fan module used in an OCX1100 switch:

Figure 1: Fan Module Used in an OCX1100 Switch
Fan Module Used in an OCX1100
Switch
Caution

You must remove only one fan module at a time for replacement from the rear panel of the chassis. The switch continues to operate without thermal shutdown for a limited period of time (30 seconds) during the replacement of a fan module.

Note

Four fan modules must be installed for optimal functioning of the switch.

The fan modules are available in two models that have different airflow directions—back-to-front (air enters through the vents on the rear panel of the switch chassis), indicated by the label AIR IN (AFI), and front-to-back (air exhausts through the vents on the rear panel of the switch chassis), indicated by the label AIR OUT (AFO). Table 1 lists the available fan module models and the direction of airflow in them.

Table 1: Fan Modules in OCX1100-48SX Switches

Fan Module

Label on the Fan Module

OCX-FAN-X-AFO

AIR OUT (AFO)

OCX-FAN-X-AFI

AIR IN (AFI)

Airflow Direction in OCX1100-48SX Switch Models

Table 2 shows the direction of airflow in OCX1100-48SX switch models as shipped.

Table 2: Airflow Direction in OCX1100-48SX Switch Models

Model Number

Fan Modules and Power Supply

Direction of Airflow

OCX1100-48SX-AFO

The switch ships with four fan modules and two AC power supplies installed; all bearing the label AIR OUT (AFO).

Front-to-back—that is, air intake to cool the chassis is through the vents on the front panel of the chassis and hot air exhausts through the vents on the rear panel of the chassis.

OCX1100-48SX-D-AFO

The switch ships with four fan modules and two DC power supplies installed; all bearing the label AIR OUT (AFO).

Front-to-back—that is, air intake to cool the chassis is through the vents on the front panel of the chassis and hot air exhausts through the vents on the rear panel of the chassis.

OCX1100-48SX-AFI

The switch ships with four fan modules and two AC power supplies installed; all bearing the label AIR IN (AFI).

Back-to-front—that is, air intake to cool the chassis is through the vents on the rear panel of the chassis and hot air exhausts through the vents on the front panel of the chassis.

OCX1100-48SX-D-AFI

The switch ships with four fan modules and two DC power supplies installed; all bearing the label AIR IN (AFI).

Back-to-front—that is, air intake to cool the chassis is through the vents on the rear panel of the chassis and hot air exhausts through the vents on the front panel of the chassis.

Figure 2 shows the location of labels on the power supplies and fan modules of an OCX1100-48SX switch.

Figure 2: Location of Airflow Labels on the Power Supplies and Fan Modules of an OCX1100-48SX Switch
Location of Airflow
Labels on the Power Supplies and Fan Modules of an OCX1100-48SX Switch
  1
Airflow labels on the fan modules
  2
Airflow labels on the power supplies
Caution

Do not install:

  • AC and DC power supplies in the same chassis.

  • AC power supplies in DC switch models or DC power supplies in AC switch models.

  • Power supplies and fan modules with different airflow labels (AIR IN (AFI) and AIR OUT (AFO)) in the same chassis

  • Fan modules with different airflow labels (AIR IN (AFI) and AIR OUT (AFO)) in the same chassis.

Front-to-Back Airflow

In the OCX1100 switch models that have front-to-back airflow, the air intake to cool the chassis is through the vents on the front panel of the switch and hot air exhausts through the vents on the rear panel. See Figure 3.

Figure 3: Front-to-Back Airflow Through OCX1100-48SX Switch Chassis
Front-to-Back Airflow Through
OCX1100-48SX Switch Chassis

You must install only power supplies that have AIR OUT (AFO) labels in switches in which the fan modules have AIR OUT (AFO) labels.

Back-to-Front Airflow

In the OCX1100 switch models that have back-to-front airflow, the air intake to cool the chassis is through the vents on the rear panel and hot air exhausts through the vents on the front panel of the switch. See Figure 4.

Figure 4: Back-to-Front Airflow Through the OCX1100-48SX Switch Chassis
Back-to-Front Airflow Through
the OCX1100-48SX Switch Chassis

You must install only power supplies that have AIR IN (AFI) labels in switches in which the fan modules have AIR IN (AFI) labels.

Do Not Install AIR IN (AFI) and AIR OUT (AFO) Components in the Same Chassis

Do not install power supplies and fan modules with different airflow labels (AIR IN (AFI) and AIR OUT (AFO)) in the same chassis. If the fan modules have AIR IN (AFI) labels, the power supplies must also have AIR IN (AFI) labels; if the fan modules have AIR OUT (AFO) labels, the power supplies must also have AIR OUT (AFO) labels.

The labels on the power supplies and fan modules should match the labels on the switch chassis.

Mixing components with AIR IN (AFI) and AIR OUT (AFO) labels in the same chassis hampers the performance of the cooling system of the switch and leads to overheating of the chassis.

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

Caution

The system raises an alarm if a fan module 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.

Positioning the Switch

In front-to-back airflow, indicated by the label AIR OUT (AFO) on the fan modules and power supplies, hot air exhausts through the vents on the rear panel of the switch. In back-to-front airflow, indicated by the label AIR IN (AFI) on the fan modules and power supplies, hot air exhausts through the vents on the front panel of the switch.

In data center deployments, position the switch in such a manner that the AIR IN (AFI) labels on switch components are next to the cold aisle, and AIR OUT (AFO) labels on switch components are next to the hot aisle.