3
Table1-2 Corrosive gas concentration limits in the equipment room
Gas
Average concentration (mg/m
3
)
Maximum concentration (mg/m
3
)
SO
2
0.3
1.0
H
2
S
0.1
0.5
Cl
2
0.1
0.3
HCI
0.1
0.5
HF
0.01
0.03
NH
3
1.0
3.0
O
3
0.05
0.1
NO
X
0.5
1.0
CAUTION:
As a best practice, control the corrosive gas concentrations in the equipment room at their average
values. Make sure the corrosive gas concentrations do not exceed 30 minutes per day at their
maximum values.
To control corrosive gases, use the following guidelines:
•
As a best practice, do not build the equipment room in a place with a high concentration of
corrosive gases.
•
Make sure the equipment room is not connected to sewer, vertical shaft, or septic tank pipelines
and keep it far away from these pipelines. The air inlet of the equipment room must be away
from such pollution sources.
•
Use environmentally friendly materials to decorate the equipment room. Avoid using organic
materials that contains harmful gases, such as sulfur or chlorine-containing insulation cottons,
rubber mats, sound-proof cottons, and avoid using plasterboards with high sulfur concentration.
•
Place fuel (diesel or gasoline) engines separately. Do not place them in the same equipment
room with the device. Make sure the exhausted air of the engines will not flow into the
equipment room or towards the air inlet of the air conditioners.
•
Place batteries separately. Do not place them in the same room with the device.
•
Employ a professional company to monitor and control corrosive gases in the equipment room
regularly.
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, use the following guidelines:
•
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.
