Several years ago, my father converted a 240V subpanel to 120V by repurposing one of the 3 available insulated conductors for the ground wire and using the other 2 conductors for the hot and neutral. The #6/3 cable has no bare wire.
Now he needs 240V back at that location but wants to also retain the 120V circuits. His idea is to use bare #4 copper wire (which he has on hand) to provide the grounding conductor for this subpanel.
Will this be an acceptable solution? If he uses the bare conductor, must it be encased in conduit or can it be run, and supported, parallel to the existing cable without conduit or other protection?
I'm not worried about an inspection but I do want to ensure he is safe and doesn't cause a shock or potential fire.
