NEC 2011 article 500.8

[ahmed.attia]

article 500.8 states under (D)Temperature that:
the temperature marking specified in 500.8(C) shall not exceed the ignition temperature
of the specific gas or vapor to be encountered

now how come when the equipment is being chosen to withstand the case where the
substance will ignite and keep functioning that i will choose an equipment with T6 marking (85 degree c) while
the substance ignites at a 100 for example
in that case the equipment will be useless

 

[GoldDigger]

article 500.8 states under (D)Temperature that:
the temperature marking specified in 500.8(C) shall not exceed the ignition temperature
of the specific gas or vapor to be encountered

now how come when the equipment is being chosen to withstand the case where the
substance will ignite and keep functioning that i will choose an equipment with T6 marking (85 degree c) while
the substance ignites at a 100 for example
in that case the equipment will be useless

The maximum temperature which the equipment can produce, which might cause ignition, is a different number from the external temperature ar which the equipment can safely continue to operate.

 

[ahmed.attia]

??

??

The maximum temperature which the equipment can produce, which might cause ignition, is a different number from the external temperature ar which the equipment can safely continue to operate.

so if i need to specify an explosion proof luminaire will i not use the same temp. markings (T1-T6) to indicate that

it can withstand that temperature or there is another marking to indicate that and table 500.8(C) only indicates the

heat produced by the equipment or i've got it all wrong and there is only one marking which is for heat dissipiated

by luminaire.

 

[ahmed.attia]

500.8(4)

500.8(4)

and 500.8(4) indicates otherwise as i understood from the paragraph

 

[GoldDigger]

and 500.8(4) indicates otherwise as i understood from the paragraph

That section and the table clearly indicate the maximum surface temperature the device will reach under normal operation if the surrounding (ambient) temperature is held at 40C.
It says absolutely nothing about what ambient temperature the device can withstand when operating.
It sounds like you were asking in your original post about the maximum ambient temperature for operation. If you did not ask about that, then I misunderstood you.

If you need the device to have a surface temperature below some limit when the ambient is above 40C, then you will have to get the information for that ambient from the manufacturer or just not use the device at a higher ambient.