Class III Motor:

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augie47

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I am awaiting engineering documentation on an area. It is a closed building where a wood chipper similar to the ones used by power line clearing folks, operates and the chips are stored for later bagging and distribution.
Initial thoughts seem to indicate it will likely be classified as a Class III Div 1 Location.
In reviewing the Code (503.125), I find a requirement that allows TEFC motors but there are also temperature limitations in 503.5.
I don't recall ever having to inspect a motor in a Class III area. Would such a motor need to be marked as suitable in an Class III area or is any TEFC motor acceptable ?
If classification marking is not required, how is 503.5 addressed ? I don;t recall if an off the shelf TEFC motor has a maximum surface temperature rating.
 

rbalex

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Doing this on iPad, so it's a bit slow.

No special marking is needed. A TEFC is fine.

I doubt it will be Division I, but if you read 503.125 carefully it doesn't matter. In fact, for Class III, there's virtually no difference between Division 1 and 2. With good housekeeping it may not even need to be classified at all.
 

augie47

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Tennessee
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State Electrical Inspector (Retired)
Assuming it comes back as a Class III, do I need to be concerned about 503.5 as far as maximum temperature on my motor ?
 

rbalex

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It will relate through 430.7(A)(5). I don't have a copy of NEMA MG-1 readily available, but most Class B rise will have no problem meeting the requirement.
 

james_mcquade

Senior Member
I'm confused.
i thought that class II was for dust and class III was fiber?

if this is is for a wood chiper, wouldn't this be class II or
am i trying to read something that is not there?

thanks,
james
 

rbalex

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I'm confused.i thought that class II was for dust and class III was fiber?if this is is for a wood chiper, wouldn't this be class II oram i trying to read something that is not there?thanks,james
See Sections 500.5(D)(1) FPN No.1 or IN No.1 (depending on NEC edition) for examples of Class III materials and 500.6(B)(3) for examples of Class II, Group G dusts. "Wood" materials may be in either Class; however, unless there is a great deal of fine sanding dry wood, Class II is very unlikely.

I don't know the full process Gus is dealing with, but I believe Class III is unlikely as well.
 
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