Humidity; Altitude; Dust And Particles; Corrosion - Cisco Catalyst 6840 Series Hardware Installation Manual

Humidity

Figure 12: Catalyst 6840-X Switch Internal Air Flow
Related Topics
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 to operate at 5 to 90 percent relative humidity, with a humidity
gradation of 10 percent per hour. In storage, a system can withstand 5 to 95 percent relative humidity. 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.

Dust and Particles

Fans cool power supplies and system components by drawing in room-temperature air and exhausting heated
air out through various openings in the chassis. However, fans also ingest dust and other particles, causing
contaminant buildup in the system and increased internal chassis temperature. A clean operating environment
can greatly reduce the negative effects of dust and other particles, which act as insulators and interfere with
the mechanical components in the system. The standards listed below provide guidelines for acceptable
working environments and acceptable levels of suspended particulate matter:
• National Electrical Manufacturers Association (NEMA) Type 1
• International Electrotechnical Commission (IEC) IP-20

Corrosion

Corrosion of system connectors is a gradual process that may eventually lead to intermittent failures of electrical
circuits. The oil from a person's fingers or prolonged exposure to high temperature or humidity may corrode
the gold-plated edge connectors and pin connectors on various components in the system. To prevent corrosion,
Catalyst 6840-X Switch Series Hardware Installation Guide
24
Installing the Fan Tray, on page 62
Preparing for Installation