Wet Location?

[bphgravity]

Is it the intent of the definition, "location, wet? to include conduits installed in slabs that are on grade but isolated from the earth by a 6 mil. vapor barrier?

Keep in mind 250.52(3) which uses similar wording.

 

[cpal]

Which way does the moisture barrier allow the moisture to travel???


I struggle with this but I believe there is an argument to be made when considering the definition, that the barrier separates the slab from the earth and it is not a wet location.

Is this a philosophical question or is some one installing conductors without a W in the designator interior to a structure??

 

[lowryder88h]

wet location

wet location

Or is it a catch 22?? It seems you could go either way. Does the moisture shyphon down through the masonary or concrete slab?? Its one to ponder!!

 

[Bob NH]

Or is it a catch 22?? It seems you could go either way. Does the moisture siphon down through the masonary or concrete slab?? Its one to ponder!!

Water travels like electricity travels, from a source of higher potential to a sink of lower potential. Usually, there is considered to be water under the slab and the vapor barrier is to prevent it from coming in. If there is a source of water inside, such as a cistern, then the barrier would prevent it from going out.

One could certainly argue that a concrete slab on 6 mil polyethylene is not in "direct contact with the earth", the term used in the definition of "Locations, wet" in Article 110. The problem is that the floor is likely to be a wet location if the top surface of the floor is below ground level and subject to infiltration.

Any conduit under the slab is certainly in a wet location.

I would allow anything above the level of the surrounding ground to be considered "not a wet location" unless there is a likely source of flooding inside. If it is below ground level and not clearly protected against infiltration, then they would have to prove to me that it is not a wet location.

 

[Cavie]

Bryan, If the slab is isolated from the earth, what's up with the UFER ground?. I do believe condensation comes into play here. I have NEVER pulled a wire out of a conduit in a slab that did not have water in it.

 

[Dennis Alwon]

Bryan, If the slab is isolated from the earth, what's up with the UFER ground?. I do believe condensation comes into play here. I have NEVER pulled a wire out of a conduit in a slab that did not have water in it.

I totally agree. Around these neck of the woods if it is a slab at grade level it is considered outdoor( wet location). Thats the safe way to go with it so why not do it that way.

 

[raider1]

I too feel that condensation is a real factor to consider. I have never see a conduit in a slab that didn't have moisture in it even if it was in the middle of a building with no high water table.

Chris

 

[George Stolz]

I don't think we could technically use a vapor barrier slab for a Ufer, but I do believe it is a wet location regardless of how dry it may be, by it's residence in the Wet definition.

They could include the Sahara Desert in the "Wet Location" definition - if they did, users of the NEC would need to ignore their preconceptions and treat it as wet, when it came to wiring methods in that location.

JMO,

 

[Jim W in Tampa]

Bryan, If the slab is isolated from the earth, what's up with the UFER ground?. I do believe condensation comes into play here. I have NEVER pulled a wire out of a conduit in a slab that did not have water in it.

I have and i am also in FL.Few years back i was doing many fire jobs on residential.Often the house were gutted.What i found was that the wires to the typical islands were romex sleeved in pvc and no damage or signs of water.And i was looking.And i replaced it with romex and passed.Typical install here is house pad 2 feet or more above road,pvc a few inched under slab that has plastic on top.And i am only 50 miles north of the OP.Believe what you like but i see it as no hazard if just under house pad,not saying 2 feet just few inches.