RCD not tripping

[keefy]

OK this one has be beat!

Replaced 2 DB's (one night storage and one 24 hour) with a dual board but adapting it so I have 2 different supplies coming in. Earth is common in the boards, but then it's common throughout. Neutral is definitely split. All connected up, tested the RCD and it did not operate with the test button. Tested on ramp and it it tripped at 50 mA. Tried second and third RCD and they are all the same so I think I can rule them out.

The only way I can get the test button to work is by splitting the neutrals on the ring, at any socket! It then works fine until you put a load on then it trips out instantly.

There is a dual source storage heater which I have completely disconnected, but still this same problem occurs. Checked all connections in the right place, checked every socket.

HELP!

 

[keefy]

Quiuck update....

Now have everything bar the ring disconnected, still the same problem!

 

[highspark]

Have you disconnected the ring and tried? Polarity ok on sockets?

 

[Amp David]

Are the neutrals into and out of the RCD terminated in the correct terminals?

 

[Amp David]

Do you have a photo of it?

 

[SPARTYKUS]

Did you test all circuits first, IR, did you do Ze if so what. Just wondered what the general picture is. Is there separation of circuits, live and neutral? Maybe someone has borrowed a neutral for something from somewhere they shouldnt.
Wha
ts the I delta n of the RCDs

 

[MarkieSparkie]

You say you have disconnected all the final circuits bar the RFC, if you have done this by switching OFF single pole MCBs, disconnect the corresponding neutrals from the neutral busbar otherwise you will not have true isolation from the RCD and fault finding will be difficult if not impossible with this type of tripping fault.

 

[keefy]

OK, thanks for all the advice but I think I have it sussed now. With everything disconnected from the board, including neutrals and earths, from all the other circuits I still had a problem on the ring. What was confusing me, and bear in mind I am full of cold and did not want to work today (boo hoo), was that the neutrals one minute were causing the fault and the next seemingly not. I was inadvertently switching a fused spur and switching the fault on and off.

The installation was allegedly tested a few weeks ago by a 'testing specialist' so I came to it assuming that he had done is job properly... WRONG. In my haste to get the sockets on over lunch time so I could get warm I thought I would just switch on for the time being, and that was the start of the problems. I just got myself in a pickle with the RCD working then not working. If I had left switching on until after testing I would have found the fault quicker.

Turns out to be a N - E fault on the fused spur on the ring. Not the first time I have had a N - E fault that does wierd things so be warned.

Moral of the story, NEVER assume someone did the testing before you properly, NEVER switch on until you have tested properly, and stay in bed when you feel like crap!

Cheers.

 

[Amp David]

never presume anything

 

[1shortcircuit]

Always test the installation before commencing any work regardless of who has been there first and how recently. Only today I found yet another ring that was not a ring, all new cable just final link missing AGAIN!!!

I was in the clear because I tested the circuit first and reported my findings immediately. Made me feel good apart from the fact that it added extra time to my working day today.

 

[SPARTYKUS]

Keefy well done for getting to bottom of it.

Spent 2 hrs yesterday looking at one circuit, shower, never really worked properly, one of those nightmare jobs where the fault is intermittent...so catch it when you can. Turns out there were a number of infractions, ended up dismantling everything, in end was the neutral link in the garage style CU-the original installer had clamped onto the tri rated cables insulation, and it was just intermittently touching solder. Presented as 30V on L-N (246 L-E).

Bloke that fitted it is a lecturer apparently. Hes also run a bit of 10mm2 from the henleys to supply it (large section of single insulation showing, 10mm protected by 80 supply fuse). Hmm.