Class I, Div II and transformers

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CKMEYER

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My question may not be posed in the right forum here, but it does relate to the NEC. I am designing an electrical distribution system for a project in the Middle East and they feel they would rather have it designed to IEC/Atex standards as opposed to NEC. Often with any new project involving a classified area, I am asked about my transformer and whether it comlplies with the area classification. I actually keep a stack of photocopied 501.100-2(b) and 450.22 standards-because the transformers are 99% of the time outdoor, dry type. My question is, would anyone have any idea which IEC standard would be most likely to discuss transformer installion in a classified area? I would assume somewhere in IEC 60076, but if there is a similar section for the IEC as there is for NEC, I would appreciate any points in the right direction.

Thanks!
 
First and foremost welcome to the forum:).
... My question is, would anyone have any idea which IEC standard would be most likely to discuss transformer installion [sic] in a classified area?...
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Yes, I have an idea ? it doesn?t exist. What does exist is various recognized protection techniques permitted in Zone classified locations.

Some of the differences between the NEC and IEC have blurred over the last 15 years, especially with CENELEC and the ATEX directive; but there are still some remnants and this is one of them.

In general, before NEC ?Zones? were adopted, once a location had been classified, the NEC emphasis was identifying what types of equipment and wiring methods were acceptable; with IEC, the emphasis was determining which protection techniques could be applied in a given Zone. A major consequence was there was no ?General Purpose? equipment permitted in IEC ?Zone? classified locations.

The NEC now recognizes various protection techniques have general application, although the protection technique is still not required to be part of the marking in ?Division? classified locations. The CENELEC/ATEX implementation of IEC now requires that equipment must be marked with their appropriate Zones, as well as their Class, Group and protection technique. Technically, ?General Purpose? equipment still isn?t permitted in IEC Zones classified locations.
 
Thank you for your response, that is exactly what I was afraid of. Although, it does make my life easier in a sense, since now I only have to explain "no stamp, no good!"

Now off to learn about what they allow/disallow as far as protection schemes in a Zone 1 area...:)
 
CKMEYER said:
Thank you for your response, that is exactly what I was afraid of. Although, it does make my life easier in a sense, since now I only have to explain "no stamp, no good!"

Now off to learn about what they allow/disallow as far as protection schemes in a Zone 1 area...:)
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I am not sure there is any protection scheme approved for a large transformer in a zone 1 area. Maybe pressurization. i doubt there is a flameproof enclosure that big.
 
petersonra said:
I am not sure there is any protection scheme approved for a large transformer in a zone 1 area. Maybe pressurization. i doubt there is a flameproof enclosure that big.
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You might be surprised ;) I certainly was. (About a third of my refinery experience is IEC design.) More importantly though, they don't have to be Ex d. There are several acceptable Zone 1 protection techniques. See Section 505.8 for a few examples; Ex p is only one of them.

Forgetting US Zones, a careful evaluation of IEC Zones indicates that rather than being a subset of Division 1, Zone 1 is an intersection of Division 1 and Division 2. That is, if a facility is classified by say API RP 500, or NFPA 497 and then the same facility correctly reclassified by IEC 60079-0, there would be many locations classified Division 2 that would be reclassified Zone 1. At the "bottom end," some locations may be Unclassified under NEC but Zone 2 under IEC. The converse is also true, Unclassified under IEC but Division 2 under NEC.

The NEC simply "force-fit" Division 1 = Zone 0 + Zone 1 and Division 2 = Zone 2.
 
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That's an excellent introductiuon, sunmmary and "crash course" from the CENELEC perspective; thanks for the link.
 
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