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kev.k

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The downstaits socket circuit is tripping the RCD on my neighbours house and I can't find the problem. I disconnected the earth at the CU and turned the circuit on and it was fine so I know the problem is with the earth. It only trips the RCD when the MCB is turned on so i'm assuming it is just an earth fault and not a earth-neutral short.

I have unplugged all appliances and it was still tripping. I disconnected all sockets and sepperated the cables and am confident I have found the responsible cable, I did a insulation resitance test on the cable at 250v and the reading was 347 ohms.

The circuit was fine when they went to be last night and when they woke up this morning it had tripped.

Any ideas what could have caused this?

Thanks
 
sounds like an intermittent fault . when you say you have found the suspect cable, do you mean a section of the ring, i.e. between 2 sockets? if so double check there's nothing connected (boiler/CH is a usual cause, or maybe a fridge. is there a hidden socket/FCU anywhere . e.g. a FCU above wall units in kitchen for cooker hood, any outside lights connected via FCU.
 
sounds like an intermittent fault . when you say you have found the suspect cable, do you mean a section of the ring, i.e. between 2 sockets? if so double check there's nothing connected (boiler/CH is a usual cause, or maybe a fridge. is there a hidden socket/FCU anywhere . e.g. a FCU above wall units in kitchen for cooker hood, any outside lights connected via FCU.
If it’s none of them have a sniff to see if you can smell burning mouse behind the walls.
 
Yes I have found which leg it seems to be between 2 sockets BUT they have just said there is another socket which can't be accessed due to a new kitchen cupboard that was fitted in. This is between the 2 sockets that I believe the fault to be on so could be that. Maybe even a fixing that had slightly nicked the cable and has now only just caused the problem (house movement ove time etc)

I have advised them to go through insurance as i'm not starting to take cupboards apart and then try and put them back together but just been frustrating me so wanted to see if it sounded like I could have missed something
 
Thought of a mouse myself, the wiring is under the floors as there is a crawl space under the house so got under the and checked the cable run but no problem under there
 
first check the suspect section gor continuity. L-L, N-N, E-E. if 1 has an unusually high reading could indicate damaged cable. you will probably need to access that hidden socket, even if it means cutting a hole in the back of the cupboard.

if push come to shove, you could diss all 3 conductors of the suspect section and convert to 2 x 20A radials.
 
Thanks guys, i've passed on it I don't need this on a Sunday when the footy's on :D

Was just getting annoyed with it though and wanted to check really on what would be causing it to trip as was only doing it when the MCB was turned on. From my understanding if it is a neutral-earth fault the RCD would be tripping with the MCB off. Is that right? The RCD was staying on if the sockets MCB was off but then you try and turn the sockets MCB on then the RCD trips so am I right in thinking it is a fault with the earth only?

Thanks again
 
The fault is not the earth but is probably a fault between live conductors and earth. For future reference it is not a good idea to disconnect the earth and energise a circuit.
 
Thanks guys, i've passed on it I don't need this on a Sunday when the footy's on :D

Was just getting annoyed with it though and wanted to check really on what would be causing it to trip as was only doing it when the MCB was turned on. From my understanding if it is a neutral-earth fault the RCD would be tripping with the MCB off. Is that right? The RCD was staying on if the sockets MCB was off but then you try and turn the sockets MCB on then the RCD trips so am I right in thinking it is a fault with the earth only?

Thanks again
you should be thinking that it's a fault between L and E, not a fault on the earth only.
 
The fault is not the earth but is probably a fault between live conductors and earth. For future reference it is not a good idea to disconnect the earth and energise a circuit.
sometimes that can help with fault finding, but care has to be taken whilst doing such. keep away from small children and pets. do not pass GO.do not collect £200.
 

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