If you are up for it....
Turn off the CU, isolate the tails (if you have a switch or fuse switch between the head and CU).
Remove the cover and take a picture of the CU so we can see all the terminations, all the neutral bars, RCD's and MCB's
I still hold with the thought that the problem is a simple incorrect neutral termination.
RCD's on the out (feed) side have a blue neutral going to a terminal rail. Only neutrals from circuits on THAT RCD can be terminated.
If you have any instance of say a circuit cable on RCD 2 using the neutral rail of RCD1 the RCD will operate due to imbalence.
Have you checked that every circuit on RCD1 and RCD2 neutrals terminate on the correct neutral strip ?
Turn off the CU, isolate the tails (if you have a switch or fuse switch between the head and CU).
Remove the cover and take a picture of the CU so we can see all the terminations, all the neutral bars, RCD's and MCB's
I still hold with the thought that the problem is a simple incorrect neutral termination.
RCD's on the out (feed) side have a blue neutral going to a terminal rail. Only neutrals from circuits on THAT RCD can be terminated.
If you have any instance of say a circuit cable on RCD 2 using the neutral rail of RCD1 the RCD will operate due to imbalence.
Have you checked that every circuit on RCD1 and RCD2 neutrals terminate on the correct neutral strip ?
