Hi All,

I have a Wyler 12 way split load CU (NHrS12SL).

For various reasons, I will be having a qualified sparky do the work, but wanted to check my options...

Currently our CU has most of the power circuits on the RCD side, and 3 lighting circuits (which could maybe be reduced to 2 (combine the 2 downstairs circuits into 1 (its not a mansion). And the immersion is also on the non RCD side.

I am thinking it is time to give at least the lighting circuits RCD protection, but would like to avoid the cost of a new
Box (which would allow 2 RCDs).

Could this be done by replacing the MCBs on the non-RCD side with RCBOs, and could these be as slim as the existing MCBs? Or would it need the double width type?

Any suggestions as to which circuits to put where (without doing too much messing, or we might as well go for a new box). Current setup is 3 power radials, one ring main, cooker and a spare 32 A (which might eventually feed a second mini ring for the kitchen) on the RCD side, and as noted above, 3 lighting and 1 immersion heater on the Non-RCD.