Class 1 div 1 group d vs. Class 1 div 2

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Jonusmc

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Hello all,
My company had recently built a C1D2 machine [I was not with the company then and have no exp. with Explosion proofing machines, but am trying to remedy that], and now we have need to quote a Class 1 Div 1 Group d machine. I have yet to find what the criteria is to determine whether or not I can use a Purge system rated for that type or do I always have to use Nema/type 7 enclosures. I will need documentation to back my decision. Thanks all J
 
Jonusmc said:
Hello all,
My company had recently built a C1D2 machine [I was not with the company then and have no exp. with Explosion proofing machines, but am trying to remedy that], and now we have need to quote a Class 1 Div 1 Group d machine. I have yet to find what the criteria is to determine whether or not I can use a Purge system rated for that type or do I always have to use Nema/type 7 enclosures. I will need documentation to back my decision. Thanks all J
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Purging/Pressurizing - NFPA 496. Also see the various other Protection Technique options in Section 500.7. Most ANSI/ISA/NFPA/UL application references for the Protection Techniques are in Section 500.2

EDIT ADD: Not all the Protection Techniques in 500.7 will apply to your equipment.
 
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Robert,
thanks for the reply - I have both of those standards open on my screen. I believe I read that the use of type 7 enclosures is the only way to go unless the AHJ allows the use of appropriate purging equipment [but I can't find that document now]. Do you know of this particular requirement - or is it invalid? Or is either way allowed? And if either way is allowed, can you point me closer to the text in either standard for me to read. The text is verrrrrrry dry. Thanks J
 
An AHJ may determine if a purged/pressurized system is applicable or installed properly – just as with any installation. However, they must accept it as a Protection Technique:

500.7 Protection Techniques. Section 500.7(A) through (L) shall be acceptable protection techniques for electrical and electronic equipment in hazardous (classified) locations. [rbalex note: Underline mine]
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Purged/Pressurized is Protection Technique 500.7(D).

NFPA 496 may be reviewed here. It does require a free registration and is just as dry. It is also terribly difficult to use, but the content is all there. (It's better to have a paper or printable pdf copy)
 
I should have said the online version is terribly difficult to use. The Standard itself may be dry, but it's pretty straight-forward.
 
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