I am combining a bunch of underutilized circuits, pulling them out of the breaker panel into an 8x6x4 junction box above it where I will combine about 10 cables into 3 circuits fed to the breaker panel through one conduit and stranded wire.
- Any issue with using 1/2 inch smurf tube between the new box and the panel? Why? Because I have some from a previous project, I have connectors, it's easy.
- I believe I can run one ground wire through the tube for everything, is that right? Same size as the largest wire in use? (I think one size lower is allowed but I have no reason to do that, it's only four feet of wire).
- I believe I should run one neutral per breaker through the tube, right? I think I can combine two neutrals into one as an MWBC, but there's no good reason to do that and it creates assorted problems.
- Box fill: I'll have about 10 cables in, another few going through the box that I haven't talked about, and the conduit to the panel... total about 30 conducting wires, biggest is #10, 12 grounds, no devices ... I need about 90 cu in and I'll have almost 200. So that's good right?
- Conduit fill: Maybe 8 #12 stranded wires and a ground in a 1/2 inch NM tube .. somewhere around 35% fill I think so also good?
Is there anything else I should be aware of?
Why am I doing this (not part of the question but in case it matters): It's a 40-space panel and it's completely full. All the cables are coming in the top side, it's a terrible rat's nest above the panel that I can't tidy up because the cables are intertwined with little slack. And a solid wall of copper inside the panel above the main breaker with cables doubled and tripled up through every single knockout. This little project will significantly improve the mess both above and just inside the breaker panel.