The title ' Ever heard of this '.
Know of one installation where the 2W service to the dwelling, the water Grounding Electrode Conductor (GEC) carried approximately 2/3rds of the Grounded conductor current back to the pole mounted transformer.
As I remember, the transformer supplied 8 other dwellings.
This dwelling then had a 3W system installed and when turning 'off' all of one leg CB's the GEC still carried about 50% of the grounded service conductor current in comparison with the undgrounded conductor current.
When the ungrounded service conductor had 30A the grounded service conductor had about 15A.
The city and the local utility were not concerned.
I would have liked to check each service drop to each of the dwelling's to determine if any of the other units had the same readings.
