cliveb
Head Pro
I needed to do some work on a lighting circuit. After disabling the appropriate circuit breaker, I was surprised that cutting a cable caused the RCD on the CU to trip.
There can't have been any power on that circuit, so why did it happen?
I have a hypothesis: I think the neutrals and earths of all the circuits are tied together at the CU.
So does cutting the cable (which obviously shorts the earth to neutral) create a leakage path between neutral and earth for other circuits that are live at the time which causes the RCD to trip?
That sort of makes sense to me, but of course I could be way off.
If that is the case, it seems a little irritating that it's necessary to power down the whole house just to work on a lighting circuit.
Doing so means you can't plug a work light into a socket to see what you're doing. How do real electricians deal with this?
There can't have been any power on that circuit, so why did it happen?
I have a hypothesis: I think the neutrals and earths of all the circuits are tied together at the CU.
So does cutting the cable (which obviously shorts the earth to neutral) create a leakage path between neutral and earth for other circuits that are live at the time which causes the RCD to trip?
That sort of makes sense to me, but of course I could be way off.
If that is the case, it seems a little irritating that it's necessary to power down the whole house just to work on a lighting circuit.
Doing so means you can't plug a work light into a socket to see what you're doing. How do real electricians deal with this?