I am going to be adding a 3-wire fed subpanel to a dwelling. My understanding of the plan of attack is attached below (Please forgive my crappy, minimalistic MS-Paint schematics).
As you'll notice, the ground and neutral are bonded in both the subpanel and service panel. My concern with this is any power on the neutral bar of the sub panel will also be carried by the ground bar, and my fear is that could cause current to flow to anything that's connected to ground, such as the electric stove chassis, any computer cases, light switches, etc.
My plan, attached below (Again, MS-Paint), isolates the ground and neutral bars, and adds a ground electrode at the sub panel. My thought is that this will keep power that is on the neutral off of the ground lines, and off of any metal objects attached to ground(stove chassis, computer cases, etc).
Do my concerns with Plan A have any merit, and if so, would Plan B solve the issues I am worried about?
If Plan B doesn't address my concerns, what can be done to prevent anyone from getting shocked when they touch something that's connected to ground?
I should mention that I am aware that a 3-wire setup is not code. Adding a 4th conductor is not an option, as the person in charge doesn't have the money for that.He has been assured by a trusted, old-school electrician that a 3-wire setup will work, but will not be up to current codes. As such, code compliance isn't my goal, so much as base-line safety is.