UG Conduit Boundary Seal

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fun ee

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Location
Texas
an underground conduit run connects a general purpose area (outdoor transformer ATC) to a outdoor Class I , Div II area. I think there are exceptions that would make a seal uncessary. Yet if a boundary seal is all that is needed how can this be done without an explosion proof seal fitting? Please provide any insight on a non-explosion proof seal solution that qualifies here? Everything I see is an explosion proof fitting that is problematic with space constraints.

I am assuming ug conduit if sealed cannot be considered Class I Div I for a potential heavy than air gas accumulation from the Div II area. Welcome feedback on that assumption as well.

Thanks,

Fun EE
 

rbalex

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Location
Mission Viejo, CA
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Professional Electrical Engineer
an underground conduit run connects a general purpose area (outdoor transformer ATC) to a outdoor Class I , Div II area. I think there are exceptions that would make a seal uncessary. Yet if a boundary seal is all that is needed how can this be done without an explosion proof seal fitting? Please provide any insight on a non-explosion proof seal solution that qualifies here? Everything I see is an explosion proof fitting that is problematic with space constraints.

I am assuming ug conduit if sealed cannot be considered Class I Div I for a potential heavy than air gas accumulation from the Div II area. Welcome feedback on that assumption as well.

Thanks,

Fun EE
Assuming the application doesn't fall under Arts 511 - 515, the only possible exception applicable to eliminate seals is Section 501.15(B)(2) Ex No.(1).

That said, any sealing method that "... minimize the amount of gas or vapor within the Division 2 portion of the conduit from being communicated to the conduit beyond the seal" may be suitable [Section 500.8(A)] in light of the next sentence in 501.15(B)(2): "Such seals shall not be required to be explosionproof but shall be identified for the purpose of minimizing passage of gases under normal operating conditions and shall be accessible."

You aren't even required to use a seal fitting at all.

NOTE: Identified does not necessarily mean listed or labeled.
 

fun ee

Member
Location
Texas
Identified method

Identified method

Good. That is my understanding as well that a fitting is not required. Yet have you used or seen another method that is considered identified fitting or not. Can you use Chico without the fitting. The conduit can terminate at the stub up and the cable is going to free air to a CGB into a building bottom.

Thanks,

Chris
 

rbalex

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Staff member
Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
Based on your description, I'd probably use a sealing hub and pack it with duct seal. You should be aware there's a potential 110.3(B) issue if you don't use a compatible sealing compound. There's definitely a 110.3(B) issue if you just poured sealing compound down the raceway.
 
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