UK RCD issue baffling me

brianmoooore · 2024-10-31T23:53:27+0000

ChiliTom said:
So am I right in saying when I use a socket for a kettle the current is going from the mains through the LH RCD to the MCB to the kettle and the return current is then going down the neutral back through the LH RCD (all ok at this point) up to the neutral bar where the RH RCD neutral is also connected, but because there is a N to E fault in a circuit that side the current is instead flowing down the RH RCD neutral to the earth somewhere which then trips the RCD as there was a imbalance (due to no live current being drawn that side)

Yes, that's the general idea, but there might also be a balanced current flowing through the RH RCD as well, if the RH circuits are in use. May be 30A flowing through the live of the RH RCD, but if there's 30.02A flowing through the neutral of the same RCD, even for just a few milliseconds, then off it goes.

ChiliTom · 2024-10-31T23:56:23+0000

brianmoooore said:
Yes, that's the general idea, but there might also be a balanced current flowing through the RH RCD as well, if the RH circuits are in use. May be 30A flowing through the live of the RH RCD, but if there's 30.02A flowing through the neutral of the same RCD, even for just a few milliseconds, then off it goes.

But instead of the lighting current returning form the circuit down its neutral the sockets neutral current is going the other way trying to get to earth through the failt