OP
guest119
Just reading through my thread and am still a bit muddled, multiple answers have been given one leaning towards entering the main switch of the DB that has been added to and others have said it's the multi pole device closest to the origin as possible...
So for example if I installed a new circuit from an existing board, and this board is fed from a LV panel and this panel fed from a transformer feeder pillar oon the load side of the transformer, I would need to determine the Main switch on the feeder pillar???
Main switch at the origin is just that, not any sub board.
Overcurrent device at the origin is just that, not any subsequent breaker.
Sometimes you can source main tails size, fuses etc from drawings etc if available from maintenance or if you are lucky, in the switch room.
As regards origin, think of it as AFTER metering.