503.9A vs 503.9C

[bobby mercier]

In 503.9A they talk about how a luminaire should be built.

In 503.9C they dont mention it. Beacause i am in a Class 3 location, i think that the luminaire should be at least DUSTTIGHT

am i right

thanks

Bobby

[ October 19, 2004, 11:11 AM: Message edited by: bobby mercier ]

 

[rbalex]

Re: 503.9A vs 503.9C

Pendent mounted luminaries [503.9(C)] are also ?fixed? so 503.9(A) applies too.

The ?basic? equipment requirements for Class III are found in the second paragraph of 503.1:

Equipment installed in Class III locations shall be able to function at full rating without developing surface temperatures high enough to cause excessive dehydration or gradual carbonization of accumulated fibers or flyings. Organic material that is carbonized or excessively dry is highly susceptible to spontaneous ignition. The maximum surface temperatures under operating conditions shall not exceed 165?C (329?F) for equipment that is not subject to overloading, and 120?C (248?F) for equipment (such as motors or power transformers) that may be overloaded.

Another relevant Section to review is 500.8. Read the entire section (its long) and pay special attention to 500.8(B) Ex No. 4.

The fixtures do not necessarily need to be "Dusttight," but they do need to be marked for Class III.

 

[bobby mercier]

Re: 503.9A vs 503.9C

Originally posted by rbalex:
Pendent mounted luminaries [503.9(C)] are also ?fixed? so 503.9(A) applies too.

The ?basic? equipment requirements for Class III are found in the second paragraph of 503.1:

Equipment installed in Class III locations shall be able to function at full rating without developing surface temperatures high enough to cause excessive dehydration or gradual carbonization of accumulated fibers or flyings. Organic material that is carbonized or excessively dry is highly susceptible to spontaneous ignition. The maximum surface temperatures under operating conditions shall not exceed 165?C (329?F) for equipment that is not subject to overloading, and 120?C (248?F) for equipment (such as motors or power transformers) that may be overloaded.

Another relevant Section to review is 500.8. Read the entire section (its long) and pay special attention to 500.8(B) Ex No. 4.

The fixtures do not necessarily need to be "Dusttight," but they do need to be marked for Class III.

But could you tell me why in all wood working plants (sawmill)that we visit,luminaires are not classified at all. They are not even dusttight.

 

[rbalex]

Re: 503.9A vs 503.9C

Most likely the luminaries themselves are not actually in the Classified location. The key is to see if there is any significant sawdust buildup on them. If not, or if "good housekeeping" prevents the build up from lasting very long, then the physical location of the luminaries may not be classified. And if the material doesn't get "on" the luminaries, it probably doesn't get "in" them either. The hazard radius from the source of ignitable materials is probably less than 3 feet.

Class III is different from Class I and II, because you are really just trying to avoid a simple fire rather than a fire and explosion. If you look carefully, you see there is virtually no difference between Division 1 or 2 in Class III installations.