I'm trying to do some improvements on an existing structure that leaves me little room for maneuvering. I'll break it down as simply as possible. I have two large PVC junction boxes (completely nonmetallic) separated by a standard 2x4 stud. It's a total distance of 4 inches. I need to get 120/240 200A from one junction box to another. That's two 3/0 THWN-2 (ungrounded), one 2/0 THWN-2 (grounded), and one 2AWG THWN-2 (grounding).
I really don't want to put a 2-inch conduit between the boxes. That requires drilling a hole 2 1/2 inches in the stud, leaving only 1/2 of stud on either side. Basically, there's no stud left there (and it's a load-bearing wall).
I had a thought that I could run four 3/4" 4-inch-long PVC conduits (completely nonmetallic) tightly grouped together (just a few millimeters from each other) from one junction box, through the stud, to the other junction box and put one conductor in each conduit. Electrically, this should work perfectly. As there are no metallic components anywhere in the boxes or conduit, there should be no inducted voltages or inductive heating. But there's electrical theory, and then there's the code.
In general, the code would seem to prohibit this. I think I may have found something in the code that will support it, but it's not very clear, and I could use some help interpreting. First there's this:
300.3(B) Conductors of the Same Circuit. All conductors of the same circuit and, where used, the grounded conductor and all equipment grounding conductors and bonding conductors shall be contained within the same raceway, auxiliary gutter, cable tray, cablebus assembly, trench, cable, or cord, unless otherwise permitted in accordance with 300.3(B)(1) through (B)(4).
300.3(B)(1) is only for parallel installations and doesn't apply. 300.3(B)(2) is only for grounding and bonding conductors and doesn't apply. 300.3(B)(4) is a special rule for enclosures, pull boxes, and neutrals, and doesn't apply.
But 300.3(B)(3) is interesting, and may provide me the out I need. Maybe.
300.3(B)(3) Nonferrous Wiring Methods. Conductors in wiring methods with a nonmetallic or other nonmagnetic sheath, where run in different raceways, auxiliary gutters, cable trays, trenches, cables, or cords, shall comply with the provisions of 300.20(B). Conductors in single-conductor Type MI cable with a nonmagnetic sheath shall comply with the provisions of 332.31. Conductors of single-conductor Type MC cable with a nonmagnetic sheath shall comply with the provisions of 330.31, 330.116, and 300.20(B).
This isn't Type MI or Type MC, so the last two sentences don't apply. But the first sentence seems to leave things wide-open as long as everything is nonmetallic. It doesn't read very well, but it seems to say that the conductors can be in separate conduits as long as everything is nonmetallic. It's restricted by 300.20(B), but that doesn't seem to hinder me any:
300.20(B) Individual conductors. Where a single conductor carrying alternating current passes through metal with magnetic properties, the inductive effect shall be minimized by (1) cutting slots in the metal between the individual holes through with the individual conductors pass or (2) passing all the conductors in the circuit through an insulating wall sufficiently large for all of the conductors of the circuit.
Since everything here is non-metallic, I would be in compliance with 300.20(B). So everything here hinges on the reading of the first sentence of 300.3(B)(3). 300.3(B)(3) is listed as an exception to the requirement in 300.3(B) that all conductors be in the same conduit, and the first sentence of 300.3(B)(3) appears to permit my proposed solution, and my proposed solution complies with 300.20(B) since it never passes through anything metal.
Thoughts? Again, we're talking about 4 inches of conduit here, and I'm struggling to comply with both the electric code and the building code (can't structurally compromise the load-bearing wall).
