Barn subpanel wiring
I know 4 wires are required for subpanel wiring 2 hot, 1 neutral and 1 ground. I also know that the ground bus and neutral bus are to be isolated at the subpanel which makes sense if you have the 4 wires from the main panel. But I have never heard an explanation as to why you cannot wire the subpanel in a way similar to the main panel, with 2 hot from the main panel with no neutral or ground from main. The subpanel would have neutral and ground on connected bus bars but separate from the main panel. I know that this works and apparently without problems because I have seen this in several older barns and outbuildings in my area.