The existing (old) sub-panel is fed by 2 phases and an uninsulated neutral conductor. There is no ground bus, return conductor to the service entrance, nor connection to a ground rod. The conductors are in conduit when leaving the main panel and arriving at the sub-panel, but not in between (they're stapled to the flat roof under the roof's insulation & paper).
I want to replace the sub-panel with a modern one with safe breakers and add a ground conductor, which will be run via another route (I want to keep the project manageable, so don't want to run new conductors).
Since the neutral conductor is uninsulated, it is in contact with the sub-panel (it is in the conduit bringing the feed conductors into the sub-panel). In a sub-panel the neutral and ground are not supposed to be connected.
My question is this: How do I install this new sub-panel and new ground conductor such that the neutral and ground are separate?
JJ