I am going to be installing a 400A(320 continuous) single phase meter base on an upcoming single family dwelling job. I will have 2/0 conductors supplying a 200A panel in the house and #3 conductors supplying a separate 100A building located on the property. If the only GE that is present on site is a concrete encased electrode attached to the footing rebar, is #4 CU the largest size conductor I would be required to install? If a metal underground water pipe was present, would #2CU then have to be installed? Also, is a driven ground required at the separate building? It will be a 3 wire feed from the meter base to the building. Thanks.