Dual RCD Problem

[Richard Burns]

In addition 'I think' Richard Burns has talked in a post (and drawn some good diagrams) about the 'opposite' RCD tripping. I.e a circuit on the right of the board making the RCD on the left trip. I can't quite get my head around this as there shouldn't be an imbalance. Anyway, that's digressing and I think you should start at the beginning with your N-E tests!

I hope I have not provided unclear information.
One key thing to remember is that (barring irregular voltage transients) if an RCD or RCBO trips then the fault must be on the circuit(s) that the RCD is protecting, the fault cannot be on a circuit not connected to the RCD.

However for a neutral earth fault present on a circuit protected by the RCD, a load on a circuit not protected by the RCD can allow diverted current to flow through the NE fault on the faulty circuit and trip that RCD, however the fault is on the circuit protected by the RCD, not on the circuit that appeared to cause the RCD trip.

 

[Adam W]

When you say "dual RCD" do you mean 2 RCDs inline?