Required junction box larger than joist

Question

I have 2-2-2-4 AL SER cable running from my main panel in my unfinished basement to a sub panel in my attached garage. Since I have conduit for the last 5 to 6 feet to protect the conductors once they are on the garage wall side, information suggests I need a junction box mounted to one of the ceiling joists to splice the #2 THHN/THWN-2 wires to their corresponding conductor in the SER cable.

Using a 1-1/2 inch conduit and a straight horizontal run, tables show I need a 12 x 12 junction box. But this is larger than the width of the 2 x 10 floor joist. Is this correct?

And what is the correct method of splicing the 2-2-2-4 conductors to the the #2 THHN/THWN-2 conductors inside the junction box, do I use special connectors, or are there big wire nuts for wires this large?

Answer 1

Ok first, you do need physical protection.

You don't need to use electrical grade conduit for physical protection. Any old thing you use is fine as long as the inspector is satisfied with it. Gas pipe, something you bend on a metal brake, you name it.

When you do use (something, possibly electrical grade conduit) for physical protection, you don't need to follow chapter and verse of the rules for using electrical conduit as a wiring method. Since it is not illegal to use cable inside conduit, you can simply send the SER on down the pipe. If there is a burr at the top of the pipe you would need a fitting or clamp, e.g. at the absolute worst a connector to pipe thread, a pipe coupler, and then a threaded cable clamp.

Answer 2

Either cable all the way, and wood or conduit for protection where needed, or wires and conduit all the way. You really don't want to splice the big stuff unless you really have to.

I mentioned wood: plywood or other wood can be used to protect the cable from damage - easy and inexpensive.