Humidity; Altitude - Cisco Catalyst 9200 Series Hardware Installation Manual

Humidity

• Verify that the ambient air temperature within the enclosed or partially enclosed rack is within the chassis
• Plan ahead. A switch that is currently installed in an enclosed or partially enclosed rack might meet
Humidity
High-humidity conditions may cause moisture to enter the system, and cause corrosion of internal components
and degradation of properties such as electrical resistance, thermal conductivity, physical strength, and size.
Extreme moisture buildup inside the system may result in electrical short circuit, which may cause serious
damage to the system. Each system is rated for storage and operation in 10 to 95 percent relative humidity,
non-condensing with a humidity gradation of 10 percent per hour. Buildings in which climate is controlled
by air-conditioning in the warmer months and by heat during the colder months usually maintain an acceptable
level of humidity for system equipment. However, if a system is located in an unusually humid location, a
dehumidifier should be used to maintain the humidity within an acceptable range.

Altitude

Operating a system at high altitude (low pressure) reduces the efficiency of forced and convection cooling
and may result in electrical problems related to arcing and corona effects. This condition may also cause sealed
components with internal pressure, such as electrolytic capacitors, to fail or perform at reduced efficiency.
Cisco Catalyst 9200 Series Switches Hardware Installation Guide
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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.
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.
Preparing for Installation