Cthusky
I’ll try to keep this as short as possible. First look at Service-Equipment in the definitions then section 230.91(NEC 2002) allows the service disconnect to be located immediately adjacent to the overcurrent device (main breaker). Both the transfer switch and the distribution panel are considered service-equipment. 250.24(C) specifies that the grounding electrode conductor be connected to the service-equipment, that could be either the transfer switch or the distribution panel adjacent to the transfer switch, both are consider service-equipment. Either place you land the grounding electrode conductor, only three conductors between the transfer switch and the dist panel is all that is required between the two panels using the Edison three-wire system.
