ElectricPersonality
Member
- Location
- Philadelphia, PA
NFPA 497 show a depression in the ground identified as a trench as a class i Div i location for flammable gasses in class i div 2. I have a few questions for anyone with some experience here.
1) Correct to say that a handhole would be the same as the trench shown in NFPA 497?
2) I am trying to understand the reasoning why the trench is classified as class i div i?
2) Also, why wouldn't a lighter than air gas be considered as less of a hazard in this situation, and perhaps not be considered a class i div 1 area given there is little risk from a gas entering the handhole from above grade and the conduit seal at the equipment in the class i div 2 area would prevent gas from migrating back to an unclassified area at the other end (I am speaking specifically about an outdoor location with conduits underground except where the stub out at equipment at each end).
3) if seal offs are required, seems likely there may not be enough room to install them inside a handhole. Any practical way to provide sealing inside a handhole with limitied space. Seal the lid of the handhole instead?
1) Correct to say that a handhole would be the same as the trench shown in NFPA 497?
2) I am trying to understand the reasoning why the trench is classified as class i div i?
2) Also, why wouldn't a lighter than air gas be considered as less of a hazard in this situation, and perhaps not be considered a class i div 1 area given there is little risk from a gas entering the handhole from above grade and the conduit seal at the equipment in the class i div 2 area would prevent gas from migrating back to an unclassified area at the other end (I am speaking specifically about an outdoor location with conduits underground except where the stub out at equipment at each end).
3) if seal offs are required, seems likely there may not be enough room to install them inside a handhole. Any practical way to provide sealing inside a handhole with limitied space. Seal the lid of the handhole instead?
