Suppose I have an existing 120/240v 200amp single phase panel which the client wants to retain as a sub-panel on a new upgraded 120/208v 600amp 3p 4w service. This is a small service station being converted to a auto car wash. What changes, if any, must be made to the single-phase panel in order to make the switch. Also, must the 600amp panel be sized to include the 200amp single phase sub-panel load. Can the panels be run side-by-side with the sub-panel tapped in above the main panel so that only the CT and service & entrance conductors are sized for the total load?

Thanx in advance [Linked Image])

CAB