Problems with Dual RCD consumer unit

[Ando1972]

I have a dual RCD consumer unit which I have a fault with an RCD tripping when any of the two socket circuits are powered up.
I did find a neutral to earth fault at one of the sockets on the downstairs ring main which has been rectified and IR test proves this ok.
What I found was that when I powered everything back on for that side of the board and the RCD protecting the circuits at this side of the board was ok , did not trip.
But when I closed the RCD that protects the other circuits on the other side of the board it tripped.
I opened the MCB for the socket circuit that had initially been faulty , reset the RCD that had tripped then closed the MCB for the sockets and again this tripped.
I reset the RCD again and then one by one closed each MCB for the circuits protected by this RCD and the only circuit that tripped this on this side was the upstair socket circuit.
An IR test on this circuit was found to be ok.
Would the problem be neutrals that are possibly tied together from each side of the board somewhere , didn't have time to continue looking in to this at the time.

 

[ColJack]

sounds like crossed neutrals or lives, or maybe as you say an interlinked ring..
there's also the possibility of having the neutrals in the wrong place in the board..

 

[oharaf]

I woulkd go for the interlinked circuits, good luck finding that one!! Let us know

 

[Ando1972]

If this was the case would the RCD that is protecting the ring circuit that was repaired not also trip?

 

[bongos]

If this was the case would the RCD that is protecting the ring circuit that was repaired not also trip?

I would have thought they would both trip as you would have a L/N imbalance on both. Bit like they do when you discover a shared neutral on the lights...