RCD tripping, advice

[bartkusal]

Hello, to everyone, would like some clues and ideas please, from obviously more experienced members on this forum.
Have attended the call out from customer, apparently his sockets don’t work. The board is old with plug in BS1361 cartridge fuses, as soon as I put the only one ring circuit fuse in it, then it trips the RCD which serves other 4 circuits, so I know obviously the fault is in the ring, wanted to do the full 3 step test on it but access in the board is terrible where you need to take the casings apart but they all imbedded sort of in the wall and stuff. It is inthe council flat. The only quick test in the board I done is line end to end which was fine, then with all the cables in their terminals I checked the continuity between them, I got the continuity between all of them on that circuit which is obviously wrong. Started going through the flat and opening sockets etc. all good, no works has been done, no nails through the walls, was wondering about squashed cable somewhere, finally found the offending part of that ring. It is a heating system which is taped of through FCU of one of the sockets,with boiler and all other associated parts: timers ,thermostatic valves, pumps,room stats connected one 12 way terminal block in one of those Plan S,Y,W systems and so on, as long as I disconnect that part of the ring by just taking the fuse out of FCU, everything is fine, I am not very familiar with the heating system wiring , that it is still to be learned, I suppose it could be anything you name it, so that where my question stands what you think could bewrong, it just seems that all conductors touching each other somewhere what could cause that. Obviously The customer is all happy that he is got power back on , but wants me to look further when I have time.
Thanks everyone reading it, and all you advice will be much appreciated, thanks in advance

 

[bartkusal]

Sorry, for the gaps between words in some places, it was ok before I presed the post the thread button...

 

[Richard]

Hopefully this has taught you that the first thing to do with a fault like this is to physically disconnect everything you can from the ring to eliminate faulty appliances, which seem more often than not to clear it! As for your heating system, I can't really answer you. I would probibly try and identify exactly what the fault is (i.e l/e or n/e) and then disconnect each componant individulaly until you clear that faulty.

 

[Richard]

You may or may not find these drawings of use. Central Heating Controls and Zoning - DIYWiki

 

[Farmelectrics]

Disconnect all appliances then do your ir test if the readings are ok plug appliances back in one at a time until you locate faulty appliance

 

[Edd]

With That Colosal wall of Text i managed,, I hope to work out that with the fuse removed from the heating system then all works.

You will need to IR test the items in the heating system by disconcting (keep earths conected) each item, Zone valve, boiler, pump etc.
you should narrow it down easy, probley quicker than it took me to read that wall of text! good luck

 

[bartkusal]

Thanks Richard for your reply, yes , that was the first thing I done, disconected everything, and just becouse I seen on the board fuse named heater I presumed heating system it was on its own circuit,but obviosly that was immersion heater instead, and I just later found that FCU with boiler and everything else taped of it....thanks...live and learn ah...

 

[bartkusal]

Verry funny Edd, honest, the text was fine before I posted, sorry anyway:wink5:

 

[bartkusal]

Post now edited,thanks for your replies, will go tomorrow and have a go at finding the faulty part as per Edds advice...

 

[Swicade]

Disconnect the feed wire to the boiler itself then start testing........8/10 i've found it's been the boiler causing RCD tripping (or a component within it). If it solves the problem and the feed cable to the boiler is all ok then you need a boiler engineer to dive into the boiler itself.

IF with the boiler disconnect you still have RCD tripping then the fun starts as you've then got to go through the whole heating wiring system step by step (refer to post #4).