In the prelude to the questions, we gave away the fact this is cellular concrete
floor raceway. What we didn't give away is the detail that tells you its
defining characteristics. Basically, it consists of precast concrete blocks that
are assembled in such a way as to create a row of hollow cells through which
wiring can run. It's a system, and you use metal fittings to connect the blocks.
Also, that row created by the arrangement of cells is parallel to the direction
of the floor member. Wires also must run vertically (to get into the raceway),
and for that purpose you use a header [372.1, 372.2].
The NEC does not provide a list of "Uses Permitted" for this wiring method.
Article 372 is arranged differently from the wiring method Articles that precede
it in chapter order. There's no subsection 10 (Uses Permitted) and what normally
appears in subsection 12 is instead in subsection 3.
- You can't use it in hazardous locations or where subject to corrosion. In
commercial garages, the only place you can use it is for supplying ceiling
outlets or for extensions to the area below the floor (you can't use it the
space between these two planes) [372.3].
- There's no 372.30, either. That's because the raceway support is inherent.
For the same reason, you don't provide supports for the 2x4 wall studs in a
stick frame building when you use them to form the raceway; they are the
- You must use "suitable metal fittings" [374.2]. Connections to cabinets and other enclosures must be made with listed metal raceways and listed fittings [372.6].