The Objective: Run a combo Heat/Cool Window unit, 1 switched light and some outlets to a detached storage shed 140 ft from home. Temperature goal is 60F min in winter and 80F max in summer. Located in North Texas. One light and outlets are for rare use. This will 100% be climate controlled storage of personal items to be accessed maybe 2-3 times per month.
What I have: Home built in 2019 with 200a main panel which is 220 ft away from where the subpanel will go in the shed. Distance from main panel to exterior of the home is approx 80ft. Then I have 1 1/2 in. conduit from the house to the shed using sweeping 90 degree fittings buried at least 18 inches. This is 140 ft. Distances are as the wire runs, not the crow flies.
My plan: (Revised based on suggestions) Install XXX amp breaker in main panel. For 240V, run quantity of 4 XX gauge copper feeder wire: two live, one neutral, One ground, a distance of 220 ft to a disconnect at the shed. Disconnect goes to subpanel. Then two branch circuits: One 240v for HVAC. Other for outlets and light circuit (GFCI).
My Primary Question: What size copper wire should I use as the feeder?
I have read differing opinions on this. Some leaning on the very cautious side and some leaning on the "don't overcomplicate it" side.
If I plan for breaking amps (40) at <3% voltage drop, I'll need 2awg? If I plan for normal operating amps (20? guessing) at <3% voltage drop, I'll need 4awg? If I plan for breaking amps (40) at <8% voltage drop, I'll need 6awg? If I plan for normal operating amps (20? guessing) at <8% voltage drop, I'll need 10awg?
Also, I'm fairly sure that shed will need it's own dedicated ground rod. But will it also need a ground feeder back to the main breaker? I have read that is a new requirement but don't understand why it requires both (if correct). If so, what size wire should I use to connect? Is it just naked ground like in romex?
Any other things I need to consider that I haven't will be appreciated. I have tried by best to research existing posts and books but I'm stuck currently on what to do. Thank you.