Looking to update the electrical setup currently in my detached garage - read through many posts on here of similar projects, but nothing with exactly the same specs. Hoping to find some right answers / make sure what I'm doing makes sense.
Currently, the 12 AWG THHN being fed through conduit out to my detached garage (50 ft. from house) is being powered via a 12 AWG Romex line indoors, in a junction box on a basement wall. This is also tied to a kill switch that has a separate line, ran up to a kitchen receptacle.
1950's house, so much of the awful wiring throughout is grandfathered in I believe, but the garage is on the same circuit as many other major lines - to my kitchen lights/outlets, basement lights, etc. I currently am trying to put the garage on its own circuit, using a 40 amp double-pole breaker that is not being used in my breaker box. I'm not certain if this is a true 240V breaker, though I believe it is based on the plug in the kitchen (the breaker used to be for an electric range)
My plan is to put a subpanel in the garage with 2 breakers, a 15A for the lights and 20A for outlets (power tools will be used) I know everyone always says the bigger the better for a garage subpanel - I don't need it. Lights and those outlets are the most I'd need. Just trying to make sure I get the correct wire (8 AWG THHN-2 / THWN) but don't know specifics as far as how many hots/neutrals/etc. needed for this sub-panel, if I actually need to keep a kill switch in the house for power sent to the garage (and if so, how is this done since the current setup of Romex to THHN is not ideal?) Most of what I'm seeing in looking at THHN-2 in 8 AWG are sold as single wires, so I want to make sure I order correctly and get the wiring done well. Or is there a better solution altogether? Any help is appreciated!