Air Flow
The switch is designed to be installed in an environment where there is a sufficient volume of air available to
cool the supervisor engines, modules, and power supplies. If there are any constraints with regard to the free
flow of air through the chassis, or if the ambient air temperature is elevated, the switch environmental monitor
may then shut down the system to protect the system components.
To maintain proper air circulation through the switch chassis, we recommend that you maintain a minimum
space of 6 inches (15 cm) between a wall and the chassis and power supply unit air intakes or a wall and the
chassis and power supply unit hot air exhausts. In situations where the switch chassis are installed in adjacent
racks, you should allow a minimum space of 12 inches (30.5 cm) between the air intake of one chassis and
the hot air exhaust of another chassis. Failure to maintain adequate spacing between chassis may cause the
switch chassis that is drawing in the hot exhaust air to overheat and fail.
If you are installing your switch in an enclosed or partially enclosed rack, we strongly recommend that you
verify that your site meets the following guidelines:
• Verify that the ambient air temperature within the enclosed or partially enclosed rack is within the chassis
operating temperature limits. After installing the chassis in the rack, power up the chassis and allow the
chassis temperature to stabilize (approximately 2 hours).
Measure the ambient air temperature at the chassis air intake grill by positioning an external temperature
probe 1 inch (2.5 cm) away from the chassis left side, and centered on the chassis both horizontally and
vertically.
Measure the ambient air temperature at the power supply unit air intake grill by positioning an external
temperature probe 1 inch (2.5 cm) away from the chassis front, centered on the power supply unit section
located above the card slots.
• If the ambient intake air temperature is less than 109°F (45°C) at altitudes of 6,000 feet and below,
the rack meets the intake air temperature criterion. At altitudes above that threshold and up to 10,000
feet (3000 m), the air intake should not exceed 104°F (40°C).
• If the ambient intake air temperature exceeds this recommendation, the system may experience
minor temperature alarms and increase fan speeds in response.
• If the ambient intake air temperature equals or is greater than 131°F (55°C), the system may
experience a major temperature alarm with maximum fan speeds in response. If ambient temperature
continues to increase, system will respond with protective shut down.
• Plan ahead. A switch that is currently installed in an enclosed or partially enclosed rack might meet
ambient air temperature and air flow requirements at present. However, if you add more chassis to the
rack or more modules to a chassis in the rack, the additional heat generated might cause the ambient air
temperature at the chassis or power supply unit inlets to exceed recommended conditions which may
trigger thermal alarms.
If installation conditions for inlet temperature and airflow are marginal or not fully met, activate the fan
tray’s NEBS mode, which has more aggressive programming to address restricted spacing and elevated
ambient temperatures. This should result in reduced thermal alarms along with greater acoustic noise
and increased power consumption associated with higher fan speeds.
Cisco Catalyst 9500 Series Switches Hardware Installation Guide
26
Preparing for Installation
Air Flow
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