If I have a conduit with 6 wires (3 separate circuits), and I want them to split at some point, can I send the conduit (A) to a 4-inch square junction box and then send 2 wires to leave the junction box in conduit B, and 4 wires to leave the junction box in conduit C?
All without splicing, just continuous run through the junction box.
Also, is splicing or no-splicing recommended one way or the other?
No, there is no requirement to make splices in a junction box.
However, if you're not making any splices, and never plan to. You can use a conduit body, instead of a junction box. Conduit bodies come in various configurations, though it sounds like a simple T type conduit body would be applicable to your situation.
Yes, you can do that all day. It's a regular trick of mine.
What's more, if pass-through is the only thing happening in the junction box, it counts legally as a conduit body, and cubic inches fall under conduit body rules rather than box-fill rules, which means you can put a lot more wires "through" it.
All things being equal, not splicing a wire is better than splicing it for no reason. A properly done wire nut will not fail, but avoiding it still removes that small chance of a mistake. It's also less to inspect.
Though I like to leave 12-18" slack somewhere in case I ever need to splice off those wires.
Regardless, like any electrical box, it can't be covered up by building construction. You have to be able to access the cover without tools.
There should be no requirement for actually cutting a cable that passes through a junction box.
Of course, that depends on your local code requirements.
In terms of safety, simply passing a cable through would not normally be construed as adding to any kind of fire hazard as long as there is room in the J-box..
