Service Conductors Outside Building - NEC 230.6

[BDB]

We have multiple buildings where the service disconnecting means is not on the first floor. 230.6(2) says that raceways encased in either at least 2" of concrete or brick are considered outside of the building. The question came up methods to encase these, and I'd really appreciate thoughts from folks who have dealt with this, and installed service conductors passing through multiple floors. Here are ideas that I know of:

1. Cast in place concrete, in a vertical column about 20' high.
2. CMU wall, 8x8x16 blocks, no grout in the cells.
3. Metal stud wall with (2) layers of 1/2" concrete board, both sides.

 

[Beaches EE]

IIRC, we did a project a few years ago and the conductors were enclosed using your option 3. We did not have to transcend floors, it was all on the same level. We did have to break through CMU demising walls and butted the encasement to the block.

 

[charlie b]

I once did a design that called for your option 1. WA State requires the disconnect within 15 feet of the outer wall. The main panel was on the second level, and the ceiling of the first level was about 18 feet high (I don't remember exact dimensions). So they only needed to encase the service conductors for about 5 feet above the floor of the first level.

 

[don_resqcapt19]

In my opinion items 2 and 3 don't meet the requirements of the code language.

 

[LarryFine]

How difficult would it be to actually have them outside?

 

[BDB]

It'd be pretty tough to get them up the face of the building. Most of these have an exterior stair along the same wall as the gear, and our client doesn't really like the exposed conduits, anyways... I was trying to think of a way to form around (12) 4" c. for a service without a bunch of custom work, and I'm leaning towards a commercial Sonotube large enough to fit them all in with 2" cover all the way around.

Beaches EE, do you remember if you guys built a fire rated assembly using the cement board, or did you just wrap the conduits without using mineral wool?

 

[kwired]

In my opinion items 2 and 3 don't meet the requirements of the code language.

I second that.

Also 8x8 blocks with cells poured still doesn't give you 2 inches of concrete on all sides if using 4 inch conduit but would work with 3 inch (maybe 3.5" need to check actual dimensions) or smaller and is centered in the block.

I'd give owner cost of running up outside wall vs encasing it inside and unless owner absolutely doesn't want it outside will probably see the outside route is significantly less cost.

Service disconnect at lower level (even if outdoors or find a way to make an electrical closet with minimum needed space indoors) then run feeders through inside to the same location would not need to be encased.

 

[LarryFine]

The advantage to the outside run is that any aesthetic covering need not be 2" thick.

 

[kwired]

The advantage to the outside run is that any aesthetic covering need not be 2" thick.

Correct. Even a few mils of paint can work.