If you have a multi unit dwelling (residential) with separate services (existing) and you do a panel changeout and it had no grounding per say. To bring up to code do you run all your grounds to 1 ground rod and water main or keep each service on their own ground rods and water mains (if several to bldg all existing) ??
Where an ac system is connected to a grounding electrode in or at a building or structure, the same electrode shall be used to ground conductor enclosures and equipment in or on that building or structure. Where separate services, feeders, or branch circuits supply a building and are required to be connected to a grounding electrode(s), the same grounding electrode(s) shall be used.
Two or more grounding electrodes that are bonded together shall be considered as a single grounding electrode system in this sense.