Air Flow - Cisco 4948 - Catalyst Switch Installation Manual

Site Requirements
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Failure to observe these guidelines can damage internal chassis components.
The Catalyst 4948E and the Catalyst 4948E-F switches are equipped with internal air temperature
Note
sensors that are triggered at 104°F (40°C) generating a minor alarm and at 131°F (55°C) generating a major
alarm.

Air Flow

The Catalyst 4948E and Catalyst 4948E-F switches are designed to be installed in an environment where
there is a sufficient volume of air available to cool the chassis and the power supplies. Any constraints
placed on the free flow of air through the chassis or an elevated ambient air temperature can cause the
switch to overheat and shut down.
To maintain proper air circulation through the switch chassis, we recommend that you maintain a
minimum 6-inch (15 cm) separation between a wall and the chassis hot air exhaust. Failure to maintain
adequate spacing between chassis can cause the switch chassis that is drawing in the hot exhaust air to
overheat and fail.
If you are installing your Catalyst 4948E or Catalyst 4948E-F switch chassis in an enclosed or partially
enclosed rack, we strongly recommend that you verify that your site meets the following guidelines:
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Note
Catalyst 4948E and Catalyst 4948E-F Switch Installation Guide
2-4
Allow a 2-hour warm-up period to bring the chassis up to normal operating temperature before
turning it on for chassis that have been exposed to abnormally cold temperatures.
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 and at the chassis air exhaust grill by positioning an
external temperature probe approximately 1 inch (2.5 cm) away from the grills.
If the ambient intake air temperature is less than 104°F (40°C), the rack meets the intake air
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temperature criterion.
If the ambient intake air temperature exceeds 104°F (40°C), the system might experience minor
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temperature alarms and is in danger of overheating.
If the ambient intake air temperature equals or is greater than 131°F (55°C), the system will
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experience a major temperature alarm and shut down.
Verify that the enclosed or partially enclosed rack allows an adequate flow of air through the switch
chassis as follows:
If the difference between the measured intake air temperature and the exhaust air temperature
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does not exceed 10°C, there is sufficient airflow in the rack.
If the difference in air temperature exceeds 10°C, there is insufficient airflow to cool the chassis.
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The 10°C temperature differential between the intake and the exhaust must be determined by
taking measurements using external digital temperature probes. Do not use the chassis internal
temperature sensors to measure the temperature differential.
Chapter 2 Preparing for Installation
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