Fault on kitchen ring

[TheCodboy]

Hi all. Had a phone call about a tripping RCD. The customer had narrowed it down to the kitchen ring. When I go there,it was indeed the kitchen ring causing the tripping. Firstly checked the usual,nothing plugged in to any of the sockets. Checked the connections at the sockets,these were all fine. Checked end to ends,had continuity on L,N & E. Carried out IR between LN & E at 250v,very low reading,virtually zero. Also tested L-E N-E & L-N. All very low. Now,the cables in the kitchen are red/black and the cables at the board are Brown/Blue. There no sign of any crimps etc at the board (which by the way is a total mess). So I’m thinking hidden joints/jb could be the source of the problem?? Any pointers would be appreciated!

 

[buzzlightyear]

L,N & E. Carried out IR between LN & E at 250v,very low reading,virtually zero. Also tested L-E N-E & L-N. All very low.

how low was Ir reading clip cable possible or heat damaged on it who knows . seek and you will find it .young fish fingers.

 

[TheCodboy]

how low was Ir reading

0.03 @250v. Tried it at 500 and was about the same.

 

[buzzlightyear]

0.03 @250v. Tried it at 500 and was about the same.

start splitting the rfc.

 

[TheCodboy]

start splitting the rfc.

Well,there’s only 3 sockets on the ring. 2 of them are on a tiled wall and the other runs under the floor to the other side of the kitchen at low level for the washing machine. The 2 on the tiled wall are back to back into the garage. I was thinking about just putting a new ring in. It would probably be quicker than trying to find the fault and less of a mess to rectify. If you catch my drift.

 

[TheCodboy]

Also the previous electrician who installed a new DB about 4 years ago has written on the board “neutral fault circuit 2”. Which happens to be the kitchen ring.

 

[buzzlightyear]

Also the previous electrician who installed a new DB about 4 years ago has written on the board “neutral fault circuit 2”. Which happens to be the kitchen ring.

if you can not find it on the ring split it and put two radials in if possible .

 

[Gavin John Hyde]

start splitting the rfc.

Time to start breaking the circuit down into parts and testing each segment. then step by step find out which piece of cable or accessory has the issue.

 

[littlespark]

Why does someone change a db knowing there's a fault? Should have been fixed four years ago.

Repeat what has been suggested;- split the ring, test each individual leg.
You're going to find a hidden jb somewhere if there's a colour change. Try behind the kickboard.

 

[TheCodboy]

Why does someone change a db knowing there's a fault? Should have been fixed four years ago.

Repeat what has been suggested;- split the ring, test each individual leg.
You're going to find a hidden jb somewhere if there's a colour change. Try behind the kickboard.

The board is an absolute mess. I can’t really even see which cables are which. Really the whole lot needs tidied up and re-terminated again. I’m just thinking of time and the costs for the customer,as it looks a total mess to find the fault and rectify,whereas it would probably be quicker for me,therefore cheaper for the customer for me to put in a new ring. It’s a tiny ring and I can pick up most the sockets from the garage side. And the db is in the garage too.

 

[Highresdis]

The fault will very likely be restricted to one place. It sounds like you're comfortable with the lack of uncertainty offered by new installation work, but actually at most you'd only need to install one new leg if you can get your head round how to locate the fault.
As there are only 3 sockets (worth checking for other points that are hidden), it won't actually take long to disconnect all the cables and test at both ends of each leg, helping you to identify with certainty the leg with the fault. Then you can decide the best way to rectify.
This will also give you valuable experience in tracking down faults.
Good luck!

 

[Richard Burns]

The cable running under the floor would be a likely scenario for being trapped between floor and joist and walked on and eventually getting crushed to connect the conductors.
Because you have a low IR reading between all conductors, this indicates something odd because it is difficult without major damage to connect line, neutral and earth all together.
It might be worth measuring low ohms continuity and see if the readings are low enough to register (even though the IR says 30kΩ it may be an effective zero). If you do get readings then the lowest reading to earth will be the core that is damaged. You can also measure at each socket and nominally the lowest reading is the one closest to the fault, but the two close sockets may not have a difference.
You may find you have another unexpected connection somewhere (in the garage / outside, another spur to another appliance?) that has a faulty appliance connected, this would resolve the "all conductors connected" scenario as the fault would be carried through the connected item.
I would start by disconnecting at the washing machine socket and the board and check which leg has the fault, because you will not be easily able (presumably, unless there is a floor void) to run a new cable to the washing machine socket.

 

[Octopus]

When you have near identical readings l-n, l-e and n-e it normally means water .....

 

[sparkdog]

Like a spur under the sink with water dripping on it, had that a while ago.

 

[buzzlightyear]

Possible jb in water under floor boards i have come across a lot of them over time

 

[Midwest]

Nah, it'll be an existing socket(s) from the previous kitchen install, buried under some tiles/plaster somewhere. If fault finding, gonna take longer than running in some new cables, I'd be tempted to do that.

 

[TheCodboy]

Nah, it'll be an existing socket(s) from the previous kitchen install, buried under some tiles/plaster somewhere. If fault finding, gonna take longer than running in some new cables, I'd be tempted to do that.

This was my thought. Much quicker & easier all round.

 

[Dobes_88]

Any outside sockets potentially on the circuit?

 

[TheCodboy]

Any outside sockets potentially on the circuit?

None that I can see and the customer reckons there’s just the 3 sockets in the kitchen itself. No visible fcu’s etc.

 

[Wilko]

None that I can see and the customer reckons there’s just the 3 sockets in the kitchen itself. No visible fcu’s etc.

Hi - yes been told this by Customer a few times . Perhaps safely isolate and test L-N, first IR (250V). If IR is big, then ok - no loads still connected. If small, do continuity and if this is not o/c you should keep looking. Domestic loads typically range from about 20 Ohms to 20k Ohms. Some little device may still be connected and be faulty. Not saying its not a cabling fault, just another idea .