Figure 117: Airflow Through The Chassis - Juniper M320 Hardware Manual

M320 Multiservice Edge Router Hardware Guide

Figure 117: Airflow Through the Chassis

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During normal operation, the fans in each fan tray function at less than full speed. The
CB constantly monitors the temperatures detected by sensors on the midplane and
router components, adjusting the speed of the fans as necessary. If the router temperature
exceeds the acceptable maximum, the CB turns off the power supplies. The following
conditions automatically cause the fans to run at full speed and also trigger the indicated
alarm:
A fan fails (red alarm).
One of the fan trays is removed (yellow alarm).
The router temperature exceeds the "temperature warm" threshold (yellow alarm).
The temperature of the router exceeds the maximum ("temperature hot") threshold
(red alarm and automatic shutdown of the power supplies).
To troubleshoot the fans, follow these guidelines:
If the red alarm LED on the craft interface lights, find the source of the problem by
looking at the display on the craft interface. The number of alarm conditions, as well
as the source of each alarm, appears on the screen.
Use the CLI to check the status of the fans. For example, you can issue the following
command to get information about the source of an alarm condition:
user@host> show chassis alarms
For information about the alarms, see
on page 285.
Place your hand near the exhaust vents at the rear of the chassis to determine whether
the fans are pushing air out of the chassis.
"M320 Chassis and Interface Alarm Messages"
Copyright © 2015, Juniper Networks, Inc.