When a conduit leaves and re-enters the same classified location (e.g., Class I, Division 2)....

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sdoobs

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does the conduit need seals? In this case, the conduit is leaving a C1D2 area going underground- routed through an unclassified area to the same C1D2 area, where it stubs back up.
 
Technically, you have described two boundaries and Section 501.15(B)(2) would apply. None of the Exceptions would apply.
 
rbalex said:
Technically, you have described two boundaries and Section 501.15(B)(2) would apply. None of the Exceptions would apply.
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Agreed- leaving and entering. Working with the inspector on a variance as adding seal offs would simply be protecting each stub up from the same classified area they are in. The "spirit" of the code in this scenario doesn't seem to fit.
 
I’m not sure where my mind is at; but nhee2’s response reminded me that the seal is not required to be explosionproof. See the last sentence of Section 501.15(B)(2) main text.

Your described intallation has been discussed by CMP 14 several times. It is unlikely that boundary seals would ever be eliminated entirely in the future, but they have relaxed the idea that they are explosionproof.

The real question is how is the Class I, Division 2 location created. That is, is the location created from the same source or multiple sources? It is a common practice to make a giant Class I, Division 2 location from multiple sources in order to avoid boundary seals.

EDIT ADD: The open question now is what fitting to use as a seal fitting because Polywater doesn't meet all the requirements of 501.15(C). Its good stuff though.
 
rbalex said:
EDIT ADD: The open question now is what fitting to use as a seal fitting because Polywater doesn't meet all the requirements of 501.15(C). Its good stuff though.
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Does it have to, based on the exception to 501.15(C)?

We've also had debates internally whether 501.15(B)(2) exception 4 would apply in this case - is the underground conduit considered 'outdoor' if both risers are outdoors?
 
Thank you both for the information. But to answer your question on how the C1D2 location was created- from multiple sources. Both ends of this conduit bank stub on the edge of one giant boundary- but within the boundary. If we were able to excavate in a straight line, we could avoid this altogether. However, we essentially have to saddle out of the boundary and back in based on existing structures that interfere with "ideal" routing.
 
nhee2 said:
Does it have to, based on the exception to 501.15(C)?

We've also had debates internally whether 501.15(B)(2) exception 4 would apply in this case - is the underground conduit considered 'outdoor' if both risers are outdoors?
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both ends of these conduits stub into rated enclosures with sealed and intrinsically safe devices. Was designed to not require seals, but the inspector and engineer have slightly different interpretations of "leaving" or "entering" the classified area.
 
nhee2 said:
Does it have to, based on the exception to 501.15(C)?

We've also had debates internally whether 501.15(B)(2) exception 4 would apply in this case - is the underground conduit considered 'outdoor' if both risers are outdoors?
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CMP 14 has the same problem or did as far as I know
 
OK. Let's make a few comments that left the OP question open.

  • The 501.15 (C) Exception doesn't clarify how an “non-explosionproof” seal should be created. It leaves it to, it “…identified for the purpose of minimizing the passage of gases permitted under normal operating conditions and shall be accessible.”
  • Identified is a defined term that doesn't necessarily mean listed or labeled. So what does it mean?
  • Underground and outdoors are not specifically defined NEC terms. As of 2023 the NEC states Exception 4 applies to aboveground installations. (BTW I was the original author for the exception as submitted by API)
 
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rbalex said:
Underground and outdoors are not specifically defined NEC terms. As of 2023 the NEC states Exception 4 applies to aboveground installations. (BTW I was the original author for the exception as submitted by API)
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Interesting - i had interpreted the old language to apply to above ground only, but others had not. The new wording makes it clear.
 
rbalex said:
Identified is a defined term that doesn't necessarily mean listed or labeled. So what does it mean?
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Polywater markets and identifies in their literature as meeting 501.15(B) requirements. Although I am sure that some will find that self-evaluation insufficient.
 
nhee2 said:
Polywater markets and identifies in their literature as meeting 501.15(B) requirements. Although I am sure that some will find that self-evaluation insufficient.
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Well maybe/maybe not. That's why Section 500.8(A)(3) was written. CMP 14 couldn't convince CMP 1 to revise the definition of identified to be a bit more liberal sufficiently so we developed suitability based on FedOSHA’s definition of acceptable.
 
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