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230 •
Use in Hazardous Environments
Classification Meeting CENELEC and IEC
6.3.4 Temperature Classes
The maximum surface temperature for electrical components of explosion
protection group I is 150 °C (danger due to coal dust deposits) or 450 °C (if
there is no danger of coal dust deposit).
In line with the maximum surface temperature for all ignition protection types,
the electrical components are subdivided into temperature classes, as far as
electrical components of explosion protection group II are concerned. Here the
temperatures refer to a surrounding temperature of 40 °C for operation and
testing of the electrical components. The lowest ignition temperature of the
existing explosive atmosphere must be higher than the maximum surface
temperature.
Tab. 6-3: Temperature classes
Temperature Classes
T1
T2
T3
T4
T5
T6
The following table represents the division and attributes of the materials to
the temperature classes and material groups in percent:
Tab. 6-4: Material groups in percent
Temperature classes
T1
26.6 %
Explosion group
IIA
85.2 %
Maximum Surface
Temperature
450 °C
300 °C
200 °C
135 °C
100 °C
85°C
T2
T3
42.8 %
25.5 %
94.9 %
IIB
IIC
13.8 %
1.0 %
Ignition Temperature
of the Combustible Materials
> 450 °C
> 300 °C to 450 °C
> 200 °C to 300 °C
> 135 °C to 200 °C
>100 °C to 135 °C
> 85 °C to 100 °C
T4
T5
4.9 %
0 %
*
Number of classified materials
*
T6
Total
0.2 %
432
*
Total
501
WAGO-I/O-SYSTEM 750
Bus System
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