Lots of good information out there but wanted to confirm that what I'm learning is accurate and also ask a little about aluminum wiring.
I'm finishing my basement (one bedroom, an office, a bathroom, a utility room and a large family room area). Home built in 2014, outside of Denver, CO. My main breaker is in my garage. A while back I added some circuits to my garage and anticipating finishing the basement. I ran an additional three 20A lines to the basement. Like all the other lines, they run up the wall in the garage across the attic and then down through walls and into the basement.
As I'm now doing the rough electrical installation in the basement I'm seeing a few unanticipated needs. I see that the sump pump is running off of the same circuit as the lights (not sure if that's allowed). I also would now like electric heated floors in the bathroom and would also put a chest freezer and fridge in the basement. There are no remaining open slots in my main circuit breaker panel (150amp). Lastly, I converted my electric range to gas recently so I have a spare 40amp 240V line only a few feet above the basement. It is 3 wire + ground. See the 2 pictures for the connection.
Can I utilize this 40amp 240v line to make a subpanel in the basement?**
If so, it seems that once at a subpanel I should have plenty of power for 3-5 new 120v 15-20amp lines to be used in the basement. Is this accurate?**
As it terminates near the back of my range, I would have to splice another appropriate line to it, in a junction box, then run that line to the subpanel. Am I allowed to splice such large conductors in a junction box and run it to the new subpanel? Any special requirements? I assume still accessible to space behind range? (aka can't drywall over it)**
I've only worked with copper before. Is it best to splice it immediately to a new copper line (6ga?) or keep it aluminum back to the new subpanel? I understand I will need correct connectors for this (Polaris?)** Can anyone tell me what gauge this aluminum wire is? Hard to tell with so little showing.
Finally, do I need to protect said new conductors back to the subpanel?** It would run for about 30 feet in the floor joist spaces/unfinished spaces above ceiling line into an unfinished utility room then drop down. PVC? EMT? FMC? Seems like 1-1/8" if PVC based on 6ga conductors. And where does the conduit stop? All the way to the new subpanel box or just until ceiling line? I would prefer to flush mount it in the stud wall but open to either way. Same question for the NM 12-2 or 14-2 coming out of the new subpanel to other circuits in the basement - does it have to be protected until within the stud spaces? I've noticed some pre-existing NM cabling within FMC as they transition from stud space into the ceiling...