The end goal is to add a 50A receptacle in the garage.
Whomever installed the subpanel ran 1 inch "smurf tube" stubbed out to the ceiling which currently has no conductors. For the new outlet I plan to add a 50A GFCI breaker (the equipment involved holds a lot of liquid). I'll then pull THHN wire (this stuff), through the smurf conduit through the attic to the wall I need the outlet on, then transition to the gray PVC stuff, and run it down the wall to a surface mount box with a 50A receptacle.
The equipment will at times draw 45-47 amps, but for short periods (15-20m), most of the time it will draw less than 30A. Total run should be around 20-25ft.
First, and main question, will 8 awg THHN get it done? I've seen things about derating that indicate runs in the attic need to be lowered to 75*, which might require me to upgrade to 6 awg.
I also see reference to "terminations" which may derate it to the 60* capacities, but I don't understand what that is. Is it what the outlet is rated at?
I plan to pull two black, and two white conductors. Two black for the hot conductors, one white for neutral, and the other white I'll label green somehow (paint, tape, whatever) for the ground. This is mainly to save on costs (a 50ft roll is only $4 more than 25 ft roll).
Is there anything grossly wrong about my approach?