THE worst kind of faultWhat about a fault on another circuit that is manifesting itself when an unrelated circuit is energised?
THE worst kind of faultWhat about a fault on another circuit that is manifesting itself when an unrelated circuit is energised?
I may be missing something but I'm struggling to think of how that could be happening in the OP's case. If the sockets circuit in question really is totally unloaded (including removal of the boiler's fuse), then I can't see how "energising the circuit" (switching it's MCB on) could affect any other circuit - it would merely be "energising" a pile of cables which were not connected to anything.What about a fault on another circuit that is manifesting itself when an unrelated circuit is energised?
I am struggling to see why/how, in terms of RCD operation, that would be any different from a N-CPC fault. All an RCD knows is that there is an L-N imbalance and, if such an imbalance exists, it neither knows nor cares where the 'missing neutral current' has gone. Perhaps you could explain what you are thinking of?What about a Neutral to GROUND fault where the incoming Neutral is not at the same potential as the GROUND ( not the CPC "Earth" ) at the fault site.
Yes, but I was talking in the context of the OP's situation, not 'in general'. What you describe would be a 'permanent' situation, which would result in the RCD tripping whenever there was sufficient total load on the local network (even if there were no load within the actual installation). AIUI, in the OP's case, the RCD trips don't occur if he isolates the L of one of his sockets circuits (with no loads connected to that circuit) - so I don't see how the mechanism you describe could be responsible.<diagram>
Which could be creating a Neutral to Ground fault. If you move point B to the consumer unit neutral bar then potential difference A to B created by the Neutral current from one appliance could be enough to have a 30 mA ground current.all seems fine apart from some Cu corrosion on the wires leading to a socket on a damp wall.
Indeed - but if (as apparently in the OP's case), opening a single-pole MCB on one (totally unloaded) circuit prevents the RCD trips, that excludes a lot of the hypothetical things that could be causing the problem if that were not the case. In particular, AFAICS, it excludes any N-cpc or N-ground fault as the cause, doesn't it?My point is when looking for faults that are tripping an RCD keep an open mind about what the possible causes are.
Nothing changed on the circuit at all, nor have I hammered in any nails around the sockets! Just tested after disconnecting the faceplate entirely with the same
That's true - but in the OP's case it appears that switch off the (presumably single-pole) MCB for the circuit stops the RCD trips from occurring, which would not normally be the case if there were a N-E fault.Removing a fuse does not disconnect neutral. In the main the switch on a fused connection unit (FCU) does so ensure it is switched off.
That's the point - with everything unplugged and the boiler fuse removed (and maybe its FCU switched off), switching on the circuit's MCB should not result in any increase in load - so shouldn't result in a trip even if there were an N-E fault.I seem to remember it was you who pointed out how load will cause neutral - earth faults to trip a RCD although in this case he does say no load.
Assuming TN-C-S supply. Didn't think at time of first post but with a TT supply then earth neutral fault could trip RCD with no load.That's the point - with everything unplugged and the boiler fuse removed (and maybe its FCU switched off), switching on the circuit's MCB should not result in any increase in load - so shouldn't result in a trip even if there were an N-E fault.I seem to remember it was you who pointed out how load will cause neutral - earth faults to trip a RCD although in this case he does say no load.
Kind Regards, John
Which is the same as Neutral to GROUND ( Not Earth ) fault on a TN-C-S system. The potential that forces a current on the Neutral through the RCD sensor coil is the potential difference between the incoming Neutral and the local Ground.Assuming TN-C-S supply. Didn't think at time of first post but with a TT supply then earth neutral fault could trip RCD with no load.
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