Class 2 DIV 2 sealing method
- Thread starter Mporter4
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- Mission Viejo, CA
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- Professional Electrical Engineer
Is there a consistent pressure differential between the classified and unclassified locations? If so, which is the more positive?
- Location
- Mission Viejo, CA
- Occupation
- Professional Electrical Engineer
He was asking about Class II. Seals have little use in Class II. See 502.15. However you're correct, a 4X rating alone isn't acceptable; the enclosure must be dusttight.[502.10(B)(4)] See the notes for Table 110.20 for dusttight rated enclosures.
- Location
- Mission Viejo, CA
- Occupation
- Professional Electrical Engineer
I agree it's almost certain the enclosure is also some form of Type 3; I just don't want it to be assumed. Otherwise, assuming the wireway is also effectively dusttight, I think the OP description is probably OK - with no seals at all. Unlike Class I, where gasses are expected to enter the enclosure, Class II expects the enclosure to essentially prohibit the ingress of dusts.
I agree with you guys regarding NEMA 4X and NEMA 12 but from a manufacturers point of view it's a matter of how it is listed with UL even though it appears to be a no brainer.
Also, when NEMA 12 is considered you are talking about dust which there is a concern about it building up on top of the enclosure and its flamability which is not a concern with NEMA 4X as I had discussed as much with my engineers while employed with a transformer manufacturer. So it may not be that simple.
Also, when NEMA 12 is considered you are talking about dust which there is a concern about it building up on top of the enclosure and its flamability which is not a concern with NEMA 4X as I had discussed as much with my engineers while employed with a transformer manufacturer. So it may not be that simple.
- Location
- Mission Viejo, CA
- Occupation
- Professional Electrical Engineer
I'm not quite sure if we're at cross points or not.
Enclosures are not required to be specifically listed or marked for Class II, Division 2 [See Sect 500.8 (C)(6)(a) & (b)]; they only need to be of Type 3, 3S, 3SX, 3X, 5, 12, 12K, or 13 (dusttight) which are all "ordinary location" classifications in UL terminology. Oddly enough, while Type 4/4X basically meets all the dusttight criteria, that Type marking alone is not recognized; but, as we have mentioned, Type 4/4X enclosures are usually multi-marked as one of the other recognized Types.
Enclosures are not required to be specifically listed or marked for Class II, Division 2 [See Sect 500.8 (C)(6)(a) & (b)]; they only need to be of Type 3, 3S, 3SX, 3X, 5, 12, 12K, or 13 (dusttight) which are all "ordinary location" classifications in UL terminology. Oddly enough, while Type 4/4X basically meets all the dusttight criteria, that Type marking alone is not recognized; but, as we have mentioned, Type 4/4X enclosures are usually multi-marked as one of the other recognized Types.
It may end up being as to how ornery the AHJ is on a particular day if they allow it or not.
When I was with a manufacture who was a preferred supplier of NEMA 4X encapsulated transformers for one of the largest petroleum companies I would never approve their use in a NEMA12 environment because they weren't listed as such even though I knew how they were engineered and manufactured. To be quite frank the core and coils were the same and the enclosures were very similar with the exception of the additional details that were necessary to seal the NEMA 4X enclosure.
What it involves for the manufacturer is how you would like to market the product if differentiating it from other in your product pine as well as other manufactures, the cost to manufactures, as well as the cost of getting a UL listing
When I was with a manufacture who was a preferred supplier of NEMA 4X encapsulated transformers for one of the largest petroleum companies I would never approve their use in a NEMA12 environment because they weren't listed as such even though I knew how they were engineered and manufactured. To be quite frank the core and coils were the same and the enclosures were very similar with the exception of the additional details that were necessary to seal the NEMA 4X enclosure.
What it involves for the manufacturer is how you would like to market the product if differentiating it from other in your product pine as well as other manufactures, the cost to manufactures, as well as the cost of getting a UL listing
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