As you'll note, the floor and impartial are bonded in both the subpanel and carrier panel. My situation with that is any strength on the neutral bar of the sub panel can also be carried by way of the floor bar, and my worry is that could purpose modern-day to drift to some thing that is related to floor, which includes the electric range chassis, any laptop instances, light switches, etc. This most effective requires 2 wires, however it calls for a transformer. In this case you're making the outbuilding its own principal panel, with its very own local grounding machine. It's miles electrically isolated from the deliver by using the transformer, so neutral is regionally derived and also you do not (and should not) connect it to the main building's neutral/floor in any manner. Has been confident with the aid of a trusted, old-college electrician that a 3-twine setup will work, but will not be as much as modern-day codes. As such, code compliance isn't my aim, a lot as base-line safety is.