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NOTE: This is an unformatted excerpt from our online fire protection training library.

Classification Basics

Class I and Class II Temperatures:

From NEC 500.8(B):

Equipment shall be marked to show the class, group, and operating temperature or temperature class referenced to a 40° C ambient... The temperature class, if provided, shall be indicated using the temperature class (T Codes) shown in Table 500.8(B). The temperature class (T Code) marked on equipment nameplates shall be in accordance with Table 500.8(B). Equipment for Class I and Class II shall be marked with the maximum safe operating temperature, as determined by simultaneous exposure to the combinations of Class I and Class II conditions.

        (FPN): Since there is no consistent relationship between explosion properties and ignition temperature, the two are independent requirements.

Table 500.8(C)
Classification of Maximum Surface Temperature

Maximum
Temperature
C�        F�
450     842
300     572
280     536
260     500
230     446
215     419
200     392
180     356
165     329
160     320
135     275
120     248
100     212
  85     185      Temperature
Class (T Code)
 
T1
T2
T2A
T2B
T2C
T2D
T3
T3A
T3B
T3C
T4
T4A
T5
T6      
NOTE: This is an unformatted excerpt from our online fire protection training library.

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