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Cisco ASR 903 Router Hardware Installation Guide
OL-25178-05
Chapter2 Preparing for Installation
Site Planning
Air Flow GuidelinesCool air is circulated through the CiscoASR 903 Router by a fan tray located along the right side of the
router. Air flow is side-to-side, right to left, as shown in “CiscoASR 903 Router Chassis Air Flow”.
Figure2-1 CiscoASR 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 CiscoASR 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.
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