Utility Neutral/neutral Current Question

this topic came up on another thread but its buried pretty deep. it is my understanding from several experienced posters that under normal circumstances all neutral current should flow back to the utility neutral, not the grounded plumbing or rods.



i am trying to figure out why. bear with this simplistic example.



100a service - 3 wires in - A (hot+), B (hot-) and N (neutral).

circuit 1 on A is using 12 amps

circuit 2 on B is using 7 amps

so a total of 5 neutral current amps have to go somewhere.



they could all flow back on N, but if bonded to N at the panel is a low resistence connection to say, copper water pipes, wouldnt some of the current flow there?



is the utility neutral supposed to be so low resistence that none of the current would flow to the grounds? if that is the case i need to call my utility ASAP because a considerable amount of current flows to my main ground.



where i am struggling is i dont see how a utility pole or transformer would be any lower resistance than miles of metal plumbing and since they are bonded together, the current can choose (i know wrong word but im not an electrican or an engineer) either path
      


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