UK Fuse box problem

[Beginner's luck]

Hi all,
RCD1 (63A, 230V brand M2 model M263230) went down on my fuse box, the main switch is still on and so is RCD2.
RCD1 controls the lights, central heating and half the plugs in my house.
What puzzles me is that when I switch off all the individual circuits breakers on RCD1, I still can't switch it on, it comes off immediately but, interestingly, the lights do blink for half a second.
I thought initially the problem could be RCD1 needing to be replaced, but if so why would the lights blink when I try to switch it on?
I need to point out that I moved in in that property about 3 years ago and have had some problems before with the main going down, it was always down to the toaster or the oven.
I'm a little lost here, any advice would be greatly appreciated.
Thanks

 

[Wilko]

Hi - sorry to hear about your electrical problem. The RCD likely tripped because it detected current flowing in the earth, instead of the Live and Neutral conductors. This indicates a fault, either in the wiring or an appliance.

Step one is to remove all plugs from sockets. Then turn your central heating thermostat down and boiler controller to be off. Wait till the boiler is quiet then power it down and use the fused isolation switch to effectively disconnect it. Same goes for any dishwashers, washing machines etc. Then try to reset the RCD and tell us how you went .

Edit - just re-read your post. Boiler probably already off, so just find it’s fused connection and switch it off.

 

[Beginner's luck]

Hi, thanks for the advice, I will try tomorrow when It's bright and let you know how it went. Thankfully the shower/oven/fridge are still working, so it's not a complete disaster

 

[SJD]

It is somewhat curious that you are seeing lights briefly blink when trying to reset the RCD, despite all the MCBs being off. I'm assuming nobody was silly enough to wire the lights directly to the RCD output and not via an MCB, but it would not be the first time.

 

[pc1966]

It might be a N-E fault as switching the MCBs off just isolates the L.

 

[brianmoooore]

If there's flash from the lights when an attempt is made to reset the RCD, and the relevant MCB is off, then the supply polarity must be reversed.
It'll be a N-E fault as in between blue and green/yellow wires, but in this case the blue is live.

 

[loz2754]

Or the relevant MCB is welded permanently on

 

[pc1966]

If there's flash from the lights when an attempt is made to reset the RCD, and the relevant MCB is off, then the supply polarity must be reversed.

Well worth double-checking that the suipply polarity (i.e. L & N) is not reversed. While rare, it is a very serious fault as you have (to all intents and purposes) no overload protection on any circuit.

 

[Lucien Nunes]

OP: I would recommend calling an electrician to undertake some testing. The particular symptoms described, especially the lights flashing on when all MCBs are off, could indicate one or more dangerous faults are present that could result in fire or shock if something else goes wrong, as others have mentioned.