I plan to upgrade an older 40 amp 3 wire feeder to my shop to a safer 4 wire feeder. No issues at all running a #6 solid copper in existing conduit to an un-bonded ground bus-bar in the sub-panel. Problem I have is the Main load center for the house is mounted inside a room in the center of the house, making it not so easy to rout the ground wire from sub-panel into the main panel.
Question I have: would code allow me to connect the feeder ground wire from the detached shop sub-panel to the ufer plate for the Main Panel ? Seems this would be OK since the main panel has the bonded ground/neutral bus-bar. Thanks