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Table 300.50 - Minimum Cover Requirements (Over 1000V)

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    Table 300.50 - Minimum Cover Requirements (Over 1000V)

    So Table 300.50, Column 4 has the minimum cover requirements for "Raceways Under Buildings or Exterior Concrete Slabs, 100 mm (4 in.) Minimum Thickness" and it's 4in below 40kV.
    Based on my understanding, I need 4" between the top of my conduit and the top surface of the slab. With column 4 specifying the minimum thickness of slab as 4in, then this would mean that my conduit is buried directly below the slab, as a minimum. Is this correct?

    Then I read footnote "d", which says "The slab shall extend a minimum of 150 mm (6 in.) beyond the underground installation, and a warning ribbon
    or other effective means suitable for the conditions shall be placed above the underground installation. "
    Does this mean that I need the slab to extend 6in below the bottom of the conduit?

    For example, if installing a 6in conduit (to simplify, let's say it has an OD of 6in), this would mean slab would have a thickness of 16in (4in above conduit + 6in conduit diameter + 6in below conduit)?


    I believe that the 6" extension is on each side of the raceway for the slab on top of the raceway. So if your raceway were 6" wide your concrete slab would need to be 18" wide with 6" overhanging each side of the raceway.


    All responses based on the 2017 NEC unless otherwise noted


      I see now, this makes sense.
      This would allow 6" on each side in order to protect the conduits.
      Thanks Infinity