aaronbailey52
Member
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.
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.
