The 4/0 grid may be the GEC, or it may be a 'ground ring' that the various conductive items/equipment are 'bonded to'. ie: an equipotential grid. IF it is a 'eq grid', then it was designed or spec's by a PE/EE.
As to the motor case...sounds like a 'eq grid' to me.
Last edited by HotLine1; 05/07/13 07:33 PM.
