fitted a 12 way split board in place of old 6 way re wirable. 2 light circs, one ok, other trips rcd. dis board has 2 ways off main switch and 5 ways off each rcd. time was running out so i tried faulty circ on one of the 2 ways off main switch. mcb held but still took out one rcd. i split light circ in two and got half lights working, connected other half and rcd trips, mcb ok. all lights work if rcd is off. before you ask i had already put neutral of faulty circ into main neutral block. Dis board is Contactum , cheap, i know ! any help guys ? cheers.