If you're using RCBOs, swap for an MCB from the same maker.
If using a split way board, the so called "17th Edition" boards have
typically 3 busbars: 2 with RCD protection and one direct to the isolator.
Spare MCB on the unprotected busbar should do it.


Is this to use different RCDs for sockets and lighting ?

Reasons not to use all RCBOs ? How much more expensive or unreliable
are they than separate RCD and MCB ?


Major changes from the 16th:

RCD protection (30mA) required on:

a) All sockets (you may leave a couple out for fridge and freezer, sockets
must be marked)

b) All circuits to a location containing a bath or shower, even the feed to
the SELV transformer for any low voltage lights. This includes bedrooms
with en-suites. Sockets (except shaver sockets) 3m from zone 1.

c) In practise all circuits need RCD protection anyway, unless they are
buried 50mm or mechanically protected in other (specific and approved)
ways.

and

d) Zones in bathrooms changed - no zone 3 anymore.

e) Volt drops on final circuits used to be 4% of nominal (230V). It's now 3%
for lighting and 5% for everything else. Unlikely to be a problem.


Thanks,
Simon.