Figure 47: Cisco ASR 903 Router Chassis Air Flow
The fan trays maintain acceptable operating temperatures for the internal components by drawing in cool air
through the vents, and circulating the air through the chassis.
The following guidelines will help you plan your equipment rack configuration:
• To ensure adequate air flow through the equipment rack, we recommend that you maintain a clearance
of at least 80 mm on each side of the rack at all times.
• If airflow through the equipment rack and the routers that occupy it is blocked or restricted, or if the
ambient air being drawn into the rack is too warm, an overtemperature condition can occur within the
rack and the routers that occupy it.
• The site should also be as dust-free as possible. Dust tends to clog the router fans, reducing the flow of
cooling air through the equipment rack and the routers that occupy it, thus increasing the risk of an
overtemperature condition.
• Enclosed racks must have adequate ventilation. Ensure that the rack is not congested, because each router
generates heat. An enclosed rack should have louvered sides and a fan to provide cooling air. Heat that
is generated by the equipment near the bottom of the rack can be drawn upward into the intake ports of
the equipment above.
• When mounting a chassis in an open rack, ensure that the rack frame does not block the side intakes and
the exhaust fans.
• When rack-installed equipment fails, especially equipment in an enclosed rack, try operating the equipment
by itself, if possible. Power off all other equipment in the rack (and in adjacent racks) to give the router
maximum cooling air and clean power.
• Avoid locating the Cisco ASR 903 Router in a location in which the chassis air intake vents may draw
in the exhaust air from adjacent equipment. Consider how the air flows through the router; the airflow
direction is side to side, with ambient air drawn in from the vents located on the front right of the chassis.
• Ensure that cables do not obstruct the air-inlet and air-exhaust grid of the chassis as it may lead to improper
ventilation, overheating of the equipment, and dust accumulation.
Air Flow Guidelines for Enclosed Rack Installation
To install a Cisco ASR 903 Router in a 4-post enclosed cabinet, the front and rear doors of the cabinet must
be removed or be perforated with a minimum of 65% open area (70% for ETSI 800mm racks).
Cisco ASR 903 and ASR 903U Aggregation Services Router Hardware Installation Guide
59
Preparing for Installation
Air Flow Guidelines for Enclosed Rack Installation