Cooling System Redundancy - Cisco CRS-1 System Description

Carrier routing system 4-slot line card chassis

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Cooling System Overview

When there are no active alarms or failures, the fan control software checks temperature sensors every

Note

two to three minutes.

Thermal Alarms

Local thermal sensors (on individual cards) monitor temperatures and generate a thermal alarm when the

cooling system is not cooling properly. A temperature sensor might trip in response to elevated ambient

air temperature, a clogged air filter or other airflow blockage, or a combination of these causes. A fan

failure causes a fault message, but if no thermal sensors have tripped, the fan control remains unchanged.

When a thermal sensor reports a thermal alarm, the sensor passes the fault condition to its local service

processor (SP), which then notifies the system controller on the route processor (RP). The system

controller passes the fault condition to the SP on the fan controller. The fan control software then takes

appropriate action to resolve the fault.

When a thermal sensor trips, the fan control software tries to resolve the problem (for example, by

increasing fan speed). The software performs a series of steps to prevent chassis components from

getting anywhere near reliability-reducing, chip-destroying temperatures. If the fault continues, the

software shuts down the card or module to prevent permanent damage to the components.

Cooling System Redundancy

The redundant architecture of the cooling system allows the cooling system to continue operating even

when certain components fail. The cooling system can withstand the failure of any one of the following

components and still continue to properly cool the line card chassis:

•

When a cooling system component fails, it should be replaced within 24 hours.

Note

Cisco CRS Carrier Routing System 4-Slot Line Card Chassis System Description

3-4

Any one of the four fans in the fan tray

One or two of the four AC rectifiers in the AC power shelf

One or two of the four DC power supplies in the DC power shelf

Chapter 3

Chassis Cooling System

OL-10805-10

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