M40 Router Redundant Cooling System Components
The M40 router cooling system consists of three separate subsystems (see Figure 214):
- Impellers—Two redundant pairs of impellers (top impeller and bottom impeller) cool the Packet Forwarding Engine components (backplane, System Control Board [SCB], FPCs, and Physical Interface Cards [PICs]). During normal operation, both pairs of impellers function at less than full capacity.
- Triple fan assemblies—Three load-sharing fans cool the backplane and the Routing Engine (rear left fan, rear center fan, and rear right fan).
- Power supply integrated fan—A built-in fan cools each power supply.
Each cooling subsystem maintains a separate airflow, and each is monitored independently for temperature control. Figure 214 shows the M40 router cooling system airflow.
Temperature sensors on the backplane, the SCB, and the FPCs control the speed of the impellers. Impeller failure triggers the red alarm LED on the craft interface. If the temperature passes a certain threshold, the JUNOS software turns off the power supplies.
The M40 router is designed to run normally with all three fans sharing the load equally and running at half speed.
Figure 215 shows the M40 router cooling system impeller trays.
Figure 216 shows the M40 router air filter and fan tray.
