Odd problem with ring final

[Synapse]

I'm having a rather odd problem that I think is best described via a diagram, essentially the problem is earth continuity throughout the circuit.

So as you can see this is a fairly weird problem I'm having, if anyone has any ideas they would like to put forward it would be greatly appreciated. I should note that this may not be a completely accurate diagram as I cannot see some of the wiring so please feel free to suggest an alternate wiring layout that would cause this.

Additionally is this a major concern considering at least one earth conductor is connected?

Regards,
Paul

 

[GaryMo]

Possibly a joint, another socket or FCU in between the two sockets with a broken cpc?

It's unlikely a cpc would become open circuit in a piece of t+e with both line and neutral conductors being continuous.

 

[Spark123]

Yes, it is a major concern as if you are using a class 1 appliance and it develops a fault then the current can't flow back via the earth conductor causing the protective device to operate, you become the path for current to flow and you will receive a shock.
Could be hidden junction boxes or anything, sorting the two which are close together should be quite easy. Check the conductors are tight at both ends, then check end to end continuity of this piece of cable with a multimeter set to ohms. You should see a very low resistance.
There may be hidden connections, there may be damage to the cable. Seems there is more than one problem i.e. multiple breaks of the earth so would make me lean more towards faulty installation.

 

[TicklyT]

The faults may be in the last working socket on each side of the ring (eg 'outgoing' earth disconnected), as well as in the faulty sockets (eg 'incoming' earth disconnected).

What tests have you carried out?

 

[Synapse]

I've now solved this little problem and thought I should share it in case someone comes across the same problem where you get odd continuity results.

The reason it was showing continuity through part of the circuit was the presence of a gas hob in the middle of the circuit, this was obviously earthed via the gas pipe. This then showed that there was continuity at two of the sockets but none after the gas hob.

This was due to a broken cpc at the final socket in the ring meaning only half of the sockets on the circuit showed continuity. The final socket showed continuity because I didn't test it correctly, only measuring continuity at the top of the earth conductor instead of the actual point of connection to the socket. The sleeving itself was hiding the break.

Anyway this has now been fixed, thanks for the suggestions guys.

 

[hairyben]

When you say "continuity" are you referring to continuity of the ring or simply the presence of the specified conductor at each point?

It takes two breaks to completely lose a conductor at multiple points.

 

[Synapse]

Continuity of the ring, although this is in reference to the earth conductor only, which may not have been clear in my previous post.

 

[Spark123]

The earth conductor (CPC) should also be wired as a ring - you need to have two breaks for it to show no continuity when testing.
Final socket??

 

[Synapse]

It is.

Either I'm not explaining this correctly or you think I'm making some sort of error in my testing. I simply made the previous post to highlight that I had fixed my problem and now there is earth continuity throughout. Just to clarify I don't need any suggestions about fixing what isn't broken.

 

[Spark123]

You may have earth continuity at each point but do you have end to end CPC continuity r2 at the CU?