Cisco 7010 Replacement Instructions Manual page 5

Fan Tray
The fan tray comprises six individual axial fans and a printed circuit board (with the control circuits)
mounted on a metal plate. (See Figure 2.) The fans draw cooling air through the chassis interior to
maintain an acceptable operating temperature for the internal components. The fan tray slides into
the right side of the chassis from the noninterface processor end of the router. The fans draw air in
through the inlet vents on the opposite side of the chassis, across the processor modules and other
internal components, and out through the exhaust vents adjacent to the fan tray. Figure 4 shows a
top-down view of the chassis, with the fan tray on the far right, and the airflow path created by the
fans. The sides of the chassis must remain unobstructed to ensure adequate airflow and prevent
overheating inside the chassis.
Figure 4
Top view of router
hassis
rflow
ower supply
rflow
A fan control board on the fan tray monitors and controls the operation of the variable-speed fans.
The variable-speed feature enables quieter operation by allowing the fans to operate at less than
maximum speed when doing so provides adequate cooling air to maintain an acceptable operating
temperature for the internal components.
When the internal air temperature is within the normal operating range, the fans operate at the
slowest speed, which is 55 percent of the maximum speed. If the temperature inside the chassis
exceeds the normal range, the fan control board increases the fan speed to provide additional cooling
air to the internal components. If the temperature continues to rise, the fan control board linearly
increases the fan speed until the fans reach full speed (100 percent). If the internal temperature
exceeds the specified threshold, the system environmental monitor shuts down all internal power to
prevent equipment damage from excessive heat.
The fan control board also relays the status of the fans to the system software. All six fans in the
array must be operational. If the system detects a failed or failing fan, it displays a warning message
on the console screen. If the condition is not corrected within two minutes, the entire system will
shut down to protect the internal components against damage from excessive heat. For an example
of this display, refer to the following section, "Prerequisites."
Internal Air Flow—Top-Down View of Chassis
Service (noninterface processor) end
600W AC-Input Power Supply and Fan Tray Replacement Instructions
Chassis fans
Power supply fans
Interface processor end
Product Overview
Fan tray
Power supply
airflow
Chassis
airflow
5