I have a CU with an 80A and 63A RCDs. Soon I'll have the following circuits to split across these RCDs: B32 cooker/hob B32 kitchen ring B32 ground ring B32 upstairs ring B6 kitchen lights B6 ground lights B6 upstairs lights
What makes a sensible split?
That may also be dictated by how the wires enter the new CU. I might lump upstairs lights with kitchen lights to be separate from downstairs lights.
The rest split as per convenient. If there are a lot of computer equipment where an RCD trip would be awkward I would have that on one RCD and the rest on the other if diversity rules allow for the rating of the RCD. Other wise kitchen ring and cooker on one, and other rings on the other?
Anything with a heating element, especially cookers are notorious for tripping RCDs.
My 2p worth.
Non split CU, and everything on its own RCBO would be first choice these days.
Next best option a "high integrity" CU with a two way RCD split, and some non RCD positions as well. Stick the cooker on a RCBO, and for the kitchen ring, then do GF Ring with upstairs lights on one RCD, then 1F ring with downstairs lights and kitchen lights on the other.
If you really only want a two way split, then as above with cooker on upstairs ring RCD, and kitchen sockets on the GF ring RCD.
That's exactly what I have done when getting rid of a whole house RCD. I have not as yet replaced the previously non-RCD protected MCBs (lighting, alarm and landline phone charger) with RCBOs, but will be doing so.
Not a single nuisance trip since the change - likely due to splitting the large number of electronic devices, with leaky filter capacitors between mains and earth, across multiple RCBOs, instead of a single RCD and thus the total leakage is no longer bringing an RCD permanently close to its limit.
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