H3C Technologies H3C S7500E Series Switches - Manual (Page 14)

4
Substance Particle diameter Concentration limit
Dust (sedimentation) 75 μm to 150 μm ≤ 1.5 mg/(m 2 h)
Sand ≥ 150 μm ≤ 30 mg/m 3
The equipment room must also meet strict limits on salts, acids, and sulfides to eliminate corrosion and
premature aging of components, as shown in Table 4 .
Table 4 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
NO
2
0.04
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 to make sure the EMI levels do not exceed the compliant range.
• Use electromagnetic shielding, for example, shielded interface cables, when necessary.
• To prevent signal ports from getting damaged by over-voltage or over-current caused by lightning
strikes, only route interface cables indoors.
Grounding
Using a good grounding system to protect your switch against lightning shocks, interferences, and ESD
is essential to the operating reliability of your switch. Make sure the resistance between the chassis and
the ground is less than 1 ohm. For more information about the grounding methods of the S7500E series,
see "Installing the switch."
Power
Perform the following steps to satisfy the power supply requirements of the S7500E series: