250.52 and Definition of Wet Location

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aaronbailey52

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250.52 (2011)
Note: Concrete containing insulation, vapor barriers, films or similar items separating it from the earth isn?t considered to be in ?direct contact? with the earth.

100 (2008)
Location, Wet. Installations underground or in concrete slabs or masonry in direct contact with the earth;

For 250.52, the conclusion I've drawn from much too much googling is that there is a consensus as to it being critical for the bottom of a slab or footing to be in direct contact with the earth, i.e. no vapor barrier beneath, even though the concrete is in direct contact with the earth from the sides. Is it reasonable or is it bonkers to then consider conduit in slab on grade above a vapor barrier to be in a wet location, even though per 250.52 it is not in direct contact with the earth, even though it is???

I have a contractor who installed plenum data cables in slab on grade and several "buildings" per NEC definition of building all tied to one grounding electrode (triad tied to centrally located ground bus bar in one of them). All electrical rooms are bonded to building steel, or will be (why would they power everything up before finishing all grounding and bonding connections??? Is that stupid or are my thoughts clouded by the moisture behind my ears???). So, if my footings, etc, are not in direct earth contact, my structural steel is not a grounding electrode. But, if I'm not in direct earth contact with my slab/footings, then how do I get my plenum rated cables replaced when I'm sure they will fill up with water, eventually.
 
Even if it is a wet location (and in my opinion it is) what NEC section requires the data cables to be listed for a wet location?
 
It's not an NEC requirement, but it seems CMP data cables are generally quite permeable to water and apt to fail due to intrusion of moisture.
 
aaronbailey52 said:
It's not an NEC requirement, but it seems CMP data cables are generally quite permeable to water and apt to fail due to intrusion of moisture.
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I would think that would only be at the cut ends, not in the middle, as for embedding Cat-5 cables directly in concrete, now way would I ever do this, first crack and it breaks, and concrete does crack.

Or did you mean putting them in conduit that is embedded in the concrete?
 
In conduit. I'm unclear on the exact routing, as I stepped into this project about halfway through. Some of the conduits are in slab, only. Others I believe pass under or through the slab then underground through a courtyard to an adjacent building. I'd like to get all of the cables replaced. The ones throught he courtyard should be pretty straightforward, but the others might be tricky.

I have plenty of language in the spec to "install per manufacturer's instructions," so I guess if I can get the manufacturer on board, I won't have to have an answer ready for why the data cable conduits are in direct contact with the earth, while the foundation is not in direct contact with the earth. Then I can get both deficiencies remediated at no additional cost, due to clear violation of the specifications. Problem solved, I guess. Now if only the cable manufacturer would return my emails...
 
aaronbailey52 said:
250.52 (2011)
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aaronbailey52 said:
Note: Concrete containing insulation, vapor barriers, films or similar items separating it from the earth isn?t considered to be in ?direct contact? with the earth.



This is assuming the vapor barrier completely covers the sides. In 40 years I haven't seen this happen. If the sides are exposed to the drit then it IS NOT seperated from the earth. That's the opinion of all the AHJ's I've talked too.

It would kinda defeat the UFER Grounding process since vapor barrier is required in Florida.
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aaronbailey52 said:
This is assuming the vapor barrier completely covers the sides. In 40 years I haven't seen this happen. If the sides are exposed to the drit then it IS NOT seperated from the earth. That's the opinion of all the AHJ's I've talked too.

It would kinda defeat the UFER Grounding process since vapor barrier is required in Florida.
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I would think either the UFER works or the vapor barrier works. I can't see how they would both work.
 
Vapor barrier

Vapor barrier

Cavie said:
aaronbailey52 said:
250.52 (2011)
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aaronbailey52 said:
Note: Concrete containing insulation, vapor barriers, films or similar items separating it from the earth isn?t considered to be in ?direct contact? with the earth.



This is assuming the vapor barrier completely covers the sides. In 40 years I haven't seen this happen. If the sides are exposed to the drit then it IS NOT seperated from the earth. That's the opinion of all the AHJ's I've talked too.

It would kinda defeat the UFER Grounding process since vapor barrier is required in Florida.
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I agree, the UFER would be non-compliant. The IRC R403.1 requires foundation footer to be in contact with the native soil(hardpan) with the stemwalls to be mastic sealed. In addition, a 1" insulation cover is required over the exterior side foundations with adjoining heated structures. With due respect, the footer will not have a barrier overlap under the footer to meet code unless the local jurisdiction adopts an exception. Is this the case?
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Different areas have different construction methods.

I can't recall seeing a footing with a vapor barrier or insulation. I see slabs and foundation walls with vapor barriers and insulation.
 
Foundation code in Florida?

Foundation code in Florida?

realolman said:
I would think either the UFER works or the vapor barrier works. I can't see how they would both work.
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The NEC 2011 changes seem to lack requirements covering this vapor barrier issue in 250.52(A)(3). I wonder if Florida is addressing amendments pinpointing the use of vapor barriers and slab footer/stemwall insulation usage limitations to comply with the IRC 403?
 
I suppose it's obvious why you'd want a vapor barrier and insulation in a poured floor, but I can't imagine why you'd want it in a footer.
 
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