another rcd query

[ezekiel]

if you add a new socket to existing installation (and other requirements are not met) then circuit needs rcd protection (yes?)

if the circuit is already rcd protected is that ok? even if the rcd was protecting half or all the original installation.

 

[luminaire]

if you add a new socket to existing installation (and other requirements are not met) then circuit needs rcd protection (yes?)

Yes, because the extended bit of cable also needs to be RCD protected.

if the circuit is already rcd protected is that ok? even if the rcd was protecting half or all the original installation.

Yes, otherwise every time you do a minor alteration to a circuit you would have to do a CU upgrade, which is not very practicable if you think about it.