On 19/03/2019 13:39, PeterC wrote:
The CU is a Wylex from the early '90s ('91 - 2 IIRC). All MCB, 30mA RCD on
rings, cooker, shower etc. and 100mA on lighting circuits.
As I'd need 30mA on the lights for the fitting in the bathroom I thought of
replacing the two MCBs with miniature Wylex RCBOs, so it's 100mA - 30mA.
I rather like the mini-RCBOs as they are 2-pole.
Would this be a valid arrangement (assuming that the RCBOs will actually
fit!)?


If the 100mA RCD is time delayed then this is correct.

However even if the 100mA RCD is not time delayed then you not made the
situation worse and complied with the 17th edition on bathroom lighting
circuits.

--
Adam