I've been doing a lot of reading and planning for a run of 8/3 NM-B that is required for a new oven/micro combo in our kitchen remodel. We currently have 10/2. While I have quite a bit of basic home and other electrical experience, we want to be sure that we add this new run properly since I haven't done that before.
I've already started running the 8/3 and began about 1/3rd of distance by cutting out some ceiling and running one end down through an exposed HVAC return vent in the kitchen wall, through a few studs behind the fridge, and have wired it up to the installed oven next to there.
The other end of the wire is a lot more fun since the house is 2 story without attic access anywhere. From the opened ceiling above a walkway, we intend to bring the 8/3 down into 1" EMT behind some new large cove moulding for about 6 feet, then into the wall and down about 6ft to run through a fireblock and under our stairs (an unfinished and not exposed area that I'm having to cut into from garage to access). From there we'll go back up the insulated exterior garage wall on the opposite side of the stairs. At that point I'll add a surface mount 4x4x1.5 steel box, and then 1" EMT again along the garage ceiling and into the wall above the panel.
I know all about protecting the romex from damage (hence the EMT behind cove moulding and on garage ceiling), as well as stapling in the wall every 4' and securing the EMT to the ceiling, as well as most of the other basics.
My main questions though before we work on the rest of this:
1) Is it ok to have this cable non-continuous? It may be significantly easier to run this cable through some of the EMT bends in the garage by having a splice (with junction box and proper #8 wire nuts of course) in at least one place, but obviously continuous wire (and especially ground) is better. Additionally we bought a 125ft bundle but the total run should only be about 60-70ft, so that's a lot of extra to pull.
2) For the EMT to wall transitions in the garage, is it best to use a junction box? I imagine so because the connection from there to EMT can be very solid, and then the hole at the back of the junction box is centered and provides more distance from the edge of the wall surface to the wire (1.25" distance NEC rule).
3) For the ceiling to EMT (behind cove moulding) to wall transitions, should we use bent EMT pipe through the sheetrock with tightened Romex to EMT adapters on the ends within the ceiling/wall, or could we just use a straight EMT pipe and add nailing plates on the back of the cove moulding at the ends where the cable comes out and goes into the ceiling/wall? The latter seems easier since I don't have a 1" EMT bender (though realize I have to find one for the garage ceiling work).
4) We have to add a new 40A double pole breaker in the panel for this. Is it recommended to try and match the existing brand/model breakers exactly?
5) Should we upgrade this circuit to AFIC? We don't currently have any and I'm not sure of the usefulness only on a 240v to oven/micro combo.