Shared/borrowed neutral?

[ac1995]

Hi,
I have an ongoing issue with an RCD which keeps tripping when bathroom light (not on RCD) is turned off.

The issue doesn’t happen every time the bathroom light is switched off but only ever trips when I turn it off. It happens mainly at night and there doesn’t seem to be much of a link otherwise to anything else in the house.

I’ve had an electrician round who tested at CU for multiple issues including shared neutral but said that wasn’t the case…

I have very basic electrical knowledge and just don’t understand how one circuit can affect another if they’re not linked? Any explanation or thoughts/advice would be greatly appreciated!

 

[littlespark]

Did the electrician test the rcd itself with an rcd tester?

This makes sure it trips within the stated time of 40ms, but can also test at what threshold it trips at.
Perhaps age has caused it to become weaker and tripping out at the slightest thing.

 

[ac1995]

Did the electrician test the rcd itself with an rcd tester?

This makes sure it trips within the stated time of 40ms, but can also test at what threshold it trips at.
Perhaps age has caused it to become weaker and tripping out at the slightest thing.

Hi yes they did test the RCD itself and all seems to be fine - the guy thought it must a faulty appliance/plug but I still don’t understand how it only trips when the light is turned off since the lighting circuit and sockets are separate circuits and the lights aren’t covered by an RCD, thanks