H3C Technologies H3C S5820V2 Series Switches - Manual (Page 10)

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• Lasting low relative humidity can cause washer contraction and ESD and bring problems including
loose captive screws and circuit failure.
• High temperature can accelerate the aging of insulation materials and significantly lower the
reliability and lifespan of the switch.
For the temperature and humidity requirements of different switch models, see " Appendix A Chassis
views and technical specifications ."
Cleanliness
Dust buildup on the chassis might result in electrostatic adsorption, which causes poor contact of metal
components and contact points, especially when indoor relative humidity is low. In the worst case,
electrostatic adsorption can cause communication failure.
Table 1 Dust concentration limit in the equipment room
Substance Concentration limit (particles/m³)
Dust ≤ 3 x 10 4 (no visible dust on the tabletop over three days)
NOTE:
Dust diameter ≥ 5 μm
The equipment room must also meet limits on salts, acids, and sulfides to eliminate corrosion and
premature aging of components, as shown in Table 2 .
Table 2 Harmful gas limits in the equipment room
Gas Maximum concentration (mg/m 3 )
SO
2
0.2
H
2
S 0.006
NH
3
0.05
Cl
2
0.01
EMI
All electromagnetic interference (EMI) sources, from outside or inside of the switch and application
system, adversely affect the switch in the following ways:
• A conduction pattern of capacitance coupling.
• Inductance coupling.
• Electromagnetic wave radiation.
• Common impedance (including the grounding system) coupling.
To prevent EMI, perform the following tasks:
• If AC power is used, use a single-phase three-wire power receptacle with protection earth (PE) to
filter interference from the power grid.
• Keep the switch far away from radio transmitting stations, radar stations, and high-frequency
devices.