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Class II, Division 2 Enclosures

Class II, Division 2 Enclosures

Class II, Division 2 Enclosures

(OP)
NEC 502.4(B)(4) requires all boxes and fittings to be "dusttight".  NEC 500.2 defines dustight as "enclosures constructed so that dust will not enter under specified test conditions".  It has a fine print note:

FPN: See ANSI/ISA 12.12.01-2000, Nonincendive Electrical Equipment for Use in Class I and II, Division 2, and Class III, Divisions 1 and 2 Hazardous (Classified) Locations , and UL 1604-1994, Electrical Equipment for Use in Class I and II, Division 2 and Class III Hazardous (Classified) Locations.

I would assume the ANSI/ISA 12.12.01-2000 deals mostly with instrumentation.  Looking at the scope of UL 1604-1994 (not wanting to pay over $500 just for the standard) it appears that UL 1604 applies mostly to equipment and not to enclosures just by themselves (although the equipment may be in an enclosure).

I would normally assume that a NEMA 4, 6, or 12 enclosure would be "dusttight", however the Hoffman Catalog in their NEMA standards table for applications specifically mentions "non-hazardous" and also states that for dust, lint, fibers, and flyings that they are not to be Class II.  

I have not seen any enclosures specifically UL 1604 listed.  MY QUESTIONS ARE THESE:  What do most people use for boxes and enclosures in a Class II, Division 2 location?  Does anyone know of enclosures specifically rated for Class II, Division 2 locations?  PLEASE NOTE THAT "DUSTTIGHT" IS NOT THE SAME AS "DUST-IGNITIONPROOF", WHICH IS A NEMA 9 CLASSIFICATION OR EXPLOSIONPROOF WHICH IS A NEMA 7 CLASSIFICATION.

RE: Class II, Division 2 Enclosures


It is possible that Hoffman doesn't feel that testing required to establish a NEMA type 7 NRTL listing is cost effective, or too great a liability if misapplied by the end user.
  
I believe there has been a similar problem with their NEMA type 12 and “JIC” enclosures substituted for type 3, 3R, 4 and 4X (!) duty.
  

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