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Cooling System and Airflow in a JSA7800 Device

The cooling system in an JSA7800 device consists of three 8038 fan modules that provide 7000 RPM, 4-pin pulse width modulation (PWM). These fan modules are internal to the chassis, that is, they are NOT hot-insertable or hot-removable.

The airflow for JSA7800 is from front-to-back. This means that cool air is taken in from the front of the chassis, and the hot exhaust air is sent out the back of the chassis.

The AC power supplies used for these units is a 920W output, Juniper P/N: 640-059999. Like the chassis, the airflow on this AC power supply is also front-to-back. These fans operate using the “super-quiet” feature which reduces noise-levels of the fans considerably. This is achieved by controlling the speed of the fans to be just enough to provide adequate cooling as opposed to just running them fast all the time.

Figure 1: Airflow for JSA7800Airflow for JSA7800

Fan Module Status

You can check the status of fan modules through the show system alarms command or by looking at the Information LED on the front panel that indicates the fan status.

Figure 2: JSA7800 Information LEDJSA7800 Information LED
Table 1: Information LED Status

Information LED State

Description

Solid Red

Indicates an overheat condition, which might be caused by cables obstructing the airflow in the system or the ambient room temperature being too warm.

Red (blinking)

Indicates a fan failure. Check for an inoperative fan.

Red (slowly blinking)

Indicates a power failure. Check for a non-operational power supply.

Solid blue

Indicates that the local UID has been activated. Use this function to locate the server in a rack mount environment.

Blinking blue

Indicates that the remote UID is on. Use this function to identify the server from a remote location.

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

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.