Dennis Alwon said:
I just came back from a long walk off a short pier and I was thinking. Unusual for me, but nonetheless, I was thinking.
If I stub a pipe down from the panel into a crawl space put a junction box on it and run thhn wire in the conduit spliced below to NM cable. Is this not legal??? Certainly it is... It is also the same heat situation as a pipe stubbed down with romex in it. Heat travels up in both cases. Yeah? or Nay?
Altho the 10foot piece in 312.5(C)X doesn?t have to be terminated in a box at its top end just like other short raceway sections [300.10X1 + 300.18(A)X], its common to limit the length to 2feet which allows different wirefill. . If you were running the conduit to a jbox, the odds are much lower that you would be able to get that jbox mounted within 2 feet. . If you go over the 2feet limit of Chapter9Tables NotetoTables(4), then 334.80, T310.16, + T310.15(B)(2)(a) become more restrictive than 240.4(D) for 14 + 12gauge wire after you get more than 9 wires in the pipe.
But if you can get the jbox under the panel within 2feet or run multiple HR pipes with each having no more than 9 CCC, then your idea would work.
Side note: When you go over the 2foot mark, on a 120/240 single phase residential, T310.15(B)(2)(a) counts 14/2 the same as 14/3 and 12/2 the same as 12/3 because the neutral doesn?t count as a CCC when all hot conductors of the system are present in the run in question. . So you?re better off running Romex multis for HRs.
David