I personally would say that's a very reasonable common sense approach, and probably even compliant withthe regs, given that you have given due consideration to the possibility that a single fault could give rise to an unacceoptable level of 'danger or inconvenience'. However, as I'm sure you understand, some people will automatically regard having all circuits covered by a single RCD as 'very poor design' (and probably non-compliant with regs) regardless of any considerations of the actual circumstances of the installation concered (and quite possibly without even giving any thought to such considerations).yep, sure John I understand that. But in this case, I think we can treat it like a submain to a garage/outbuilding, and protect it by a 30ma RCD with MCB's protecting the individual circuits downline. Reason being, I can run the lights in the stairway (with the door to the garage) from the existing house circuit so you're not plunged into darkness. Also, as it is just a bedroom, bathroom and garage, there is no normal instance where an earth fault would occur at night.
I suppose one can argue that, given the vagueness of the regs, there is an implied requirement that not only should the circuits be divided but also that they be divided in such a fashion as to minimise 'danger and inconvenience'. Mind you, as I implied in an earlier post, even if things are arranged so that the sockets circuit remains live in the location of a lighting circuits failure, many (perhaps even most) houses won't have any lighting plugged in to any sockets, let alone turned on, at a time when the lighting circuit fails!Sod's law also means that the electrician has put the lights on the same side of the split-load board as the plug sockets, so it defeats the object of split-loading the board for separate RCD protected circuits in the first place. Strange there isn't any requirement to separate circuit types according to use on a split load board. hmmm.
Kind Regards, John