The Cisco CRS 8-Slot Line Card Chassis Enhanced router cooling system dissipates the heat generated by the routing system and controls the temperature of components in the chassis. The cooling system has a fully redundant architecture that allows the routing system to continue operating with a single-fault failure (such as a single fan or fan tray failure).

The architecture also supports a redundant load-sharing design.

The complete chassis cooling system includes:

• Two fan trays. Each fan tray contains four fans.
• Temperature sensors (on cards and modules throughout the chassis).
• Control software and logic.
• An air filter, inlet and outlet air vents, and bezels.
• Blanks and impedance carriers for empty chassis slots.
• Modular configuration AC and DC PMs have their own fans.

All four fans in a fan tray operate as a group. So if it is necessary to increase or decrease airflow, all fans in the tray increase or decrease their rotation speed together. When two fan trays are operational in a chassis, the speed of fans in both trays is adjusted together.

Thermal sensors (inlet, exhaust, and hot-spot) located throughout the Cisco CRS 8-slot Line Card Chassis Enhanced router are used to monitor temperature readings and identify when the system is not cooling properly.