390 Underfloor Raceways.

Underfloor raceways include raceways and associated components designed and intended for installation beneath or flush with the surface of a floor for the installation of cables and electrical conductors.
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Underfloor raceways include raceways and associated components designed and intended for installation beneath or flush with the surface of a floor for the installation of cables and electrical conductors.

MA amendments.

390.23. Revise this section to read as follows:

390.23 Ampacity of Conductors. The ampacity adjustment factors in 310.15(C)(1) shall not apply where 30 or fewer current-carrying conductors occupy no more than 20 percent of the interior cross-sectional area of underfloor raceways.

Click here to see the Massachusetts amendments to the 2023 NEC®.

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390 Underfloor Raceways.

Below is a Real Question from our Electrical Continuing Education Courses for Electrical License Renewal:

Which of the following is true regarding Underfloor Raceways installed in Massachusetts?

A: The ampacity adjustment factors in 310.15(C)(1) apply when more than 30 current-carrying conductors occupy more than 20 percent of the interior cross-sectional area of underfloor raceways.
B: The ampacity adjustment factors in 310.15(C)(1) never apply.
C: The ampacity adjustment factors in 310.15(C)(1) shall apply to all conductors installed in underfloor raceways.
D: The ampacity adjustment factors in 310.15(A) shall apply to all conductors installed in underfloor raceways.
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