Tripping out BOTH RCDs

[robsparx]

did a cu change on friday. tt system, simple split load board, dual rcds. Theres a fault on one of the lighting circuits. when one of the light switches is turned on it trips out BOTH rcds on the CU.

going back to the house shortly to further investigate. would this be a borrowed neutral on the lighting circuit?

 

[tenheads]

defo borrowed neutral common fault now with these bleedin rcd,s no way to sort it other than rewire it

 

[piz]

Hello A bit new to this game but have expirenced this! since then before I change a cu check continuity on all neturals the only ones that have continuity should be the ring main if the lighting circuit has continuity would be easy to tell customer more money to fix the fault
also tell them if you change fuse board will show up faults on old cookers washers etc
Nic say it is ok to leave on same circuit if you make a note in the cert at customers request

 

[andekoch]

Landing lights seem to have this problem when wired in days of old (as mentioned in a previous reply). Sometimes it is easier to run a neutral from the CU to the offending light from the appropriate RCD. First saw this on the CU change I was using for my NIC visit as well.