PTX12008 Cooling System

Fan Trays

Each fan tray contains five dual rotating fans, a non-removable control board, LEDs, and two handles on the front faceplate. The fans in the fan trays have n+1 redundancy─if one fan rotor fails, the remaining fans operate at a higher speed to maintain proper cooling.

The fan trays are hot-insertable and hot-removable field-replaceable units (FRUs): You can remove and replace them without powering off the router or disrupting router functions.

You can install the fan trays in the fan tray slots on the rear panel of the chassis. The fan trays install vertically, side by side, below the power shelf.

In addition to the fans in the fan trays, there is an internal built-in fan in each power supply module (PSM) that helps to cool the PSM components.

The system continuously monitors the temperature of critical parts across the chassis and adjusts the chassis fan speed according to the temperature. The Junos OS Evolved controls the fan speed. Under normal operating conditions, the fans in the fan trays run at less than full speed. If one fan tray fails or appears missing (such as when a Switch Interface Board (SIB) is being replaced), the other fan trays set the fans to full speed. This behavior ensures that the router continues to operate normally as long as the remaining fans cool the chassis sufficiently. Use the show chassis fan command to see the status of individual fans and fan speed. If the maximum temperature specification is exceeded and the system cannot be adequately cooled, the Routing and Control Board shuts down some or all of the hardware components.

See Table 1 for the specifications of the fan trays.

Table 1: Fan Tray Specifications

Specification	Value
Number of fans per fan tray	5
Number of fans per chassis	15
Fan numbering	0 through 4
Volume flow per chassis at 100% fan speed at 77 °F (25 °C)	3170 cubic feet per minute (CFM) when 3 kilowatt (kW) AC/HVAC/HVDC PSMs are installed in all the PSM slots 3350 CFM when DC PSMs are installed in all the PSM slots
Volume flow of the power shelf at 100% fan speed at 77 °F (25 °C) with 3 kW AC/HVAC/HVDC PSMs installed in all the PSM slots	320 CFM
Volume flow of the power shelf at 100% fan speed at 77 °F (25 °C) with DC PSMs installed in all the PSM slots	500 CFM
Height	27.55 in. (69.98 cm)
Width	5.04 in. (12.8 cm)
Depth	4.3 in. (10.9 cm) not including handles; 5.5 in. (14 cm) including handles
Weight	19.3 lb (8.8 kg)

Airflow

The PTX12008 has a front-to-back cooling system. Air flows into the chassis from the ports in the Flexible PIC Concentrators (FPCs) and Routing and Control Boards (RCBs) installed on the front panel of the chassis, passes through the SIBs, and exits from the fan trays and the PSMs installed on the rear panel of the chassis.

Fan Tray LEDs

Each fan tray has one LED labeled FAN TRAY and three LEDs collectively labeled SIB STATUS. The FAN TRAY LED represents the status of the fans in the fan tray. The SIB STATUS LEDs represent the status of the SIBs installed behind the fan tray. The LEDs are located in the top-left corner of the fan trays.

Table 2: Fan Tray and SIB Status LEDs

Name	Color	State	Description
FAN (Fan status)	Green	On steadily	All the fans are operating normally. The system has verified that the fan tray is engaged, that the airflow is in the correct direction, and that all the fans are operating correctly.
	Green	Blinking	The fans are starting up, but are not completely ready.
	Yellow	Blinking	An error is detected in one or more fans in the fan tray. Replace the fan tray as soon as possible. Either the fan has failed or it has become disconnected. To maintain proper airflow through the chassis, leave the fan tray installed in the chassis until you are ready to replace it.
	None	Off	The fan is not receiving power from the fan tray.

The SIB status LEDs are described in SIB Status LEDs.