Wire in a conduit in a slab

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Depends. If the slab is on grade with dirt below it then you cannot use NM cable as the raceway interior is considered a wet location.
 
Since it's a kitchen island I would assume that it's a short run with 2 elbows. 12-2 UF will work just size the raceway accordingly.
 
A few comments:

- I would think that compacted base rock is not the same as earth, and so the definition of "Location, Wet" does not automatically make the slab a wet location.

- As the slab is not above grade, even if the slab is a wet location, 300.9 does not tell us that the interior of a conduit in it is a wet location.

- 300.5(B) tells us that if the conduit is underground, then the interior of the conduit is a wet location. But is "underground" the same as "below grade"?

I can see an argument that grade is the top of the slab, and underground is below the slab and base rock. In which case I would say the interior of the conduit is not a wet location. But if underground starts at the top of the slab, then the interior of the conduit is a wet location under 300.5(B).

Cheers, Wayne
 
A raceway in a concrete slab in contact with the earth is a wet location by Article 100 definition.

Location, Wet. Installations underground or in concrete slabs or masonry in direct contact with the earth; in locations subject to saturation with water or other liquids, such as vehicle washing areas; and in unprotected locations exposed to weather.
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without getting into base rock or the vapor barrier detail and whether or not is a wet location, you can either install UF cable and be done or ask the AHJ for clarifications. Install 3/4" or 1" conduit so it is easier to pull and will allow future expansion.

IMO, per NEC it is wet location (even though it may never get wet).
 
The building codes typically require the vapor barrier for the very purpose of preventing the slab from being a wet location. If the vapor barrier is installed, the slab in not in direct contact with the earth and the slab is not a wet location.
 
wwhitney said:
- As the slab is not above grade, even if the slab is a wet location, 300.9 does not tell us that the interior of a conduit in it is a wet location.

- 300.5(B) tells us that if the conduit is underground, then the interior of the conduit is a wet location.
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The interior of a conduit is not a location; the conductors are located wherever the conduit is located.
 
infinity said:
A raceway in a concrete slab in contact with the earth is a wet location by Article 100 definition.
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Indeed, which immediately raises the question of whether a slab cast again compacted base rock, rather than native soil, is "in direct contact with earth."

And I see no comments so far on whether 300.5(B) applies, i.e. whether in the slab itself is "underground".

Cheers, Wayne
 
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