both rcds trip on a dual rcd

[piz]

Hello Guys
Can you help me please I have just changed cu old wylex to dual rcd board when I test the rcd trip times on one circuit both rcds trip at 123 x1 and 40 x 5 this is a ring main circuit 32amp
I have left cu off till morning be safe prob be ok when I do rest of checks but scratching my heasd at the mo

 

[Sintra]

Hello Guys
Can you help me please I have just changed cu old wylex to dual rcd board when I test the rcd trip times on one circuit both rcds trip at 123 x1 and 40 x 5 this is a ring main circuit 32amp
I have left cu off till morning be safe prob be ok when I do rest of checks but scratching my heasd at the mo

Have you got neutral bars split correctly at cu 1 from each RCD?

You could also possibly have a borrowed neutral possibly on stair lighting circuit.

 

[piz]

Yeah netural bars split ok and ring main circuit at fault

 

[Sintra]

Yeah netural bars split ok and ring main circuit at fault

Have you tried RCD test on another circuit apart from the ring to see if only 1 trips?

 

[neil2jo]

Easiest test is run continuity between all the circuits, i.e take neutral from circuit A and test against circuit B and so on, time consuming but should reveal that you have shared phase/neutral....then you need to find where it is.

Where I stated circuit A and B. A is from a circuit on RCD1, B is from a circuit on RCD2 side

 

[Roger]

Easiest test is run continuity between all the circuits, i.e take neutral from circuit A and test against circuit B and so on, time consuming but should reveal that you have shared phase/neutral....then you need to find where it is.

Where I stated circuit A and B. A is from a circuit on RCD1, B is from a circuit on RCD2 side

Hi there,
Came across this and thought this might help me.So from CU connect to neutral circuit A with wander lead and then go round whole house and see if its common against A and B.Repeat and do with phase.
Understanding correctly ?
To help find fault could you disconnect all fasia sockets and go from one to another ? so you could identify the route of the ring .Connect neutral and phase together with socket removed and just do a continuity at next suspected socket on one of the cable in the box ,and so on and so on.This will then give a clearer idea as to where the route might have become broken or bridged and what floorboard to remove.
Fault finding is the challenge

Cheers

 

[Spudnik]

No, just IR test between a circuit N on RCD A across to a circuit N from RCD B.

You could also blanket test to start with between the 2 N bars to see if it is a borrowed N.

It should read clear.