I have a question very similar to How to attach to electrical subpanel?. I'm in Washington State, Jefferson County. PoCo is Mason PUD 1. AHJ is WA state L&I.
I want to run at least 70A, but future proof for 100A. Both panels are flush mounted, so their backs are against the exterior sheathing. I think for 100A, I want 3@2 AL XHHW-2 and 1@8 AWG bare copper. I think that fits (with spare room) in 1-1/2" Sched 40 PVC. I have (at least?) 4 90-degree elbows, as shown in the picture below. #1 is a transition from down from the main panel to run in the ground. #2 is a bend around the main building. #3 is a bend towards the outbuilding. #4 is a bend back up the wall of the outbuilding toward the panel.
First question: I've seen comments about expansion joints. Are those a must? A suggestion? We do get snow in WA, but not a lot.
Second question: I've seen comments about using Schedule 80 above grade? A must or a suggestion? There is foot traffic between the buildings (between angle 3 and 4), but that's about it. I had one inspector I talked to say 40 is fine. Might another inspector say something different?
Third question: I saw a comment in another question that XHHW-2 must be in a conduit. Does that mean I can't go straight from conduit into the panel boxes? If not, is there a wire I can use that can? I'd prefer no splices.
Fourth question: At each panel, I'll have a transition between the panel and the conduit. Is that included in the "bends"? If so, any thoughts on how I deal with the 360-degree bend limit? Moving panel placement isn't a viable option (if needed, I can go into details why).
Fifth question: What is the best transition fittings between the panels and conduit? In the question I referenced above, the suggestion was an LB (like https://www.homedepot.com/p/Carlon-1-1-2-in-Schedule-40-and-80-PVC-Type-LB-Conduit-Body-Case-of-6-E986HR/202380271). My concern with that is the building walls are thin (the outbuilding is probably 1/2" plywood - nothing else). With the panels flush-mounted inside, the back of the LB would extend maybe an inch into the box. I then saw a suggestion to add a nipple. Before I'm done, I am almost to the front of the box. And I still don't think I have a mechanical connection between this fitting and the box. Hence my question... Should I transition from PVC to metal and use something like https://www.mcmaster.com/rigid-conduit-fittings/shape~90-elbow/connectors-for-medium-wall-imc-and-thick-wall-rigid-steel-conduit/ or does that also push me over 360 degrees and again after adding a nipple, push me either far from the exterior wall or far into the box?