What level of current flow would you expect to see in the main grounding electrode conductor or in grounding conductors to ground bus in electrical rooms? Measured between 200 and 700 mA in various grounding conductors from main ground bus to ground bus in electrical rooms during a site visit to project under construction. Installed 4/0 ground conductor from main ground bus to first ground bus in each electrical room riser and extend to ground bus in each room for 6 floors.