ken m,
You mentioned running 4 wire from meter to panel. Is this a 3W 120/240V system?
Have made some calculations where, 5 feet of RMC, EMT, Alum RMC, and RNC have been the conduits between the meter and the Main-panelboard and a #6 GEC to a ground rod from the meter and a #4 GEC from the panelboard to the water grounding electrode and assumed 25 ohms between the ground rod and the underground water electrode.
For a 200A Residential 120/240V 3W 1Ø Service and using 2/0 Copper in the raceways as noted above, for a 30 ampere unbalanced load ( where one of the Ungrounded conductors carries 30A more than the other ungrounded conductor, thus the grounded conductor [ neutral ] is carrying 30 amps) the:
RMC carries about 48 percent of the 30 Amps and the 2/0 copper about 52 percent.
EMT carries about 27 percent of the 30 Amps and the 2/0 copper about 73 percent.
The Alum RMC carries about 78 percent and the 2/0 carries about 22 percent.
and the the PVC carries 0 percent.
The grounding electrode (GE) system as noted above varied from about .003A to about .01A of the 30A parallel paths of the 2/0, the raceway(s), and the GE system.
Metallic raceways do carry an appreciable amount of the grounded conductor current on an "all" metallic raceway service installation as discribed above.
There are Many thousands of such services installed.
