Hello, I have a question regarding the voltage drop calculation for a cable. How do we select the length of the cable?- Is it the one way distance between the source and the equipment or do we need to consider the return path? Can someone please explain this in detail and whether it applies to both AC and DC systems? Thank you.

I have an rv parked behind my house and tired of running extension cords all the time. Okay, I've trenched min 20 inches deep and bought a power panel prewired with circuit breakers and 1ea 50 amp outlet, 1ea 30 amp outlet and 1ea 20 amp gfci outlet. Panel is 165 feet from 100 amp sub panel in basement and will use 1 1/2" sch 40 pvc from 60 amp 2 pole cb using 3ea 4ga (hots & neutral) and 1ea 6 ga ground wire. I filled out all the permit papers and going to the building dept. I found out they "will not issue a permit for permanent power to anything with wheels". My dilemma is go ahead and do it to code and safety without permit, or refile for a sub panel for welder and gfci outlet then remove those outlets and add conduit for my rv power after final is done? They told me to remove the rv batteries and charge them inside - that I didn't need power at the rv. Your input please. Thanks