I am rewiring an old house (50s) with romex to have the flexibilitiy to run it outside conduits when necessary and to further protect the wire from creatures plus making it easier to upgrade in the future (not breaking drywall, etc). So, on the subject of emt conduit inside walls, I would imagine that given that the romex is not requried to be in conduits whilst inside walls then the fact that the romex is not inside a conduit all the way would then acceptable. The situation is depicted below:

In this particular situation the electrical box is inside the concrete exterior wall since there is a cavity in the concrete wall for the box only (and no indentation in the walls for any wire), so I can not connect the emt conduit to the box (yep, I reamed the conduit and also using bushings whenever the wires exit the conduit). Also, I don't want to drill larger holes in the joists (at least not with the exterior walls) for the conduit, so the conduit does not go all the way to the attic; and once in the attic the wire should travel in conduits unless very impractical. Given that the wire is not travelling 100% of the time inside inside the conduits I assume that derating of the conduit is not necessary and that I can fill the conduit even to 100%. Also, I would rather not drill larger holes on the joist for the conduit. I just want to double check and make sure that this is acceptable?

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    I can't quite understand what you're trying to achieve. What is the purpose of the conduit? Why are you mixing conduit and type NM cable? You mention protecting the wiring from creatures, and making it easier to upgrade in the future. Both of those are functions of conduit, so I'm not sure why you're using NM cable. – Tester101 Oct 28 '15 at 10:28
  • The conduit will further protect the wires inside the wall (nails, screws, etc), the conduit will make it much easier to upgrade, replace, or run another wire if needed. I am using nm-b because during its travel path there will be small spots whereby it is not going to be inside a conduit (I could use a junciton box to transition from romex to thnn,but it seems simply to simply employ romex). – tk3000 Oct 28 '15 at 13:00
  • If you're using conduit for protection, and to make upgrading easier. Then the conduit should be continuous from above the ceiling, to the box. Leaving gaps, means the NM cable is unprotected at some points within the wall. – Tester101 Oct 28 '15 at 13:26
  • Gaps also pretty much negate most of the "ease of upgrade" since you're going to have to tear out some wallboard to get to the end of the conduit. – JPhi1618 Oct 28 '15 at 13:57
  • yeah, but this situation is very specific due to the fact that it is an exterior concrete wall. The vast majority of the walls will not fall in this category and the conduit will go all the way to the attic. Still I have to verify whether or not the conduit could go all the way to attic (don't want to drill large hoses in important joist). At the bottom the conduit would be very close to the power outlet (there simply would be no fitting connecting the conduit to the outlet due to clearance issues in this case) – tk3000 Oct 28 '15 at 14:56

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