Underground distribution systems sealing conduits

[lectrican]

The 6th largest city in the country is making everyone seal conduits, used or not, that emerge into the bottom of a slab mount SES. They are considering the actual conduit an underground distribution system. Mike Holt's handbook, 2020, shows what I feel is correct, a panel that's mounted underground. Thoughts? Thanks...

230.8

 

[infinity]

230.8 seems pretty clear the raceways, both used and unused need to be sealed to keep air from moving through them.

230.8 Raceway Seal. Where a service raceway enters a building or structure from an underground distribution system, it shall be sealed in accordance with 300.5(G). Spare or unused raceways shall also be sealed. Sealants shall be identified for use with the cable insulation, shield, or other components.

 

[lectrican]

What about above ground distribution systems? Mikes handbook clearly depicts a basement panel.

 

[infinity]

Look at 300.5(G).

 

[lectrican]

1. How will moisture contact live parts above grade?

2. The 2020 info note concerning vapor leads to hazardous locations.

Underground is below grade. I believe this is misunderstood.

 

[kwired]

1. How will moisture contact live parts above grade?

2. The 2020 info note concerning vapor leads to hazardous locations.

Underground is below grade. I believe this is misunderstood.

Phoenix maybe one place this is not as important simply because of lower condensing probability.

Though an underground raceway that fills with condensation seals itself pretty well just like a P trap in a drain pipe does.

 

[lectrican]

None of the surrounding cities have asked for it. They might now though.

 

[tom baker]

Here in the Seattle area, we have a lot of condensation as the conduit heat up during day, cool off. Duct seal is simple and fast, there are other products I use when water is an issue, IE at the bottom of a hill.

 

[kwired]

The 6th largest city in the country is making everyone seal conduits, used or not, that emerge into the bottom of a slab mount SES. They are considering the actual conduit an underground distribution system. Mike Holt's handbook, 2020, shows what I feel is correct, a panel that's mounted underground. Thoughts? Thanks...

230.8

Not a new section or requirement, likely someone happened to notice it wasn't being enforced in the area and brought attention to it.

Looked at 2002 code and same section is pretty much identical. Pretty certain this had been a requirement before then but that is about time code made some major overhaul of how things are organized and it may have been basically same requirement but in different location in the code.

I know were dinged for not doing that back in the early to mid 1990's.