Very High end to end on cpc ring

[Luke238]

Hello,

Just getting ready for my first scheme assessment and am completing a board change to be assessed on.

Ground floor ring end to end readings. Its a 2.5mm ring T+E
r1 0.71
rn 0.72
r2 8564

I have had all of the sockets off to check for a loose connection.

The property has over the years had many alterations and additions.

Figure of 8 tests for R1 and R2 are about what i would expect (ish) 0.86 highest reading at all but one socket which is off the scale in the 8 thousands. I have replaced the socket and still the same.

Highest ZS at all sockets is 1.17

Given the Zs reading is 1.17 could I just downgrade the MCB and run the circuit off say a 20amp. There is end to end of all conductors but clearly high resistance on r2 and make a note on the EIC ? (I expect issue could be under the tiled floor).


This also got me thinking, when you guys change a board and come across faults like this would you take responsibility and try to rectify the high reading. However even with a board change it would be no less safe than when you started ?

 

[telectrix]

if you can't find the faul ( which I suspect will be close to the socket with the 8000+ R1 + R2,) dis. all 3 conductors of the faulty leg and convert to 2 x 20A radials on separate MCBs.

 

[Andy5678]

I would be looking to do some sort of repair. Re wire the damaged section or spit the ring into two radials and remove faulty section from circuit.

 

[Strima]

Wander lead and find the damaged section of cable, either replace or split into two radials as above.

 

[Lucien Nunes]

There is end to end of all conductors

Thousands of ohms doesn't really qualify as a 'conductor'! At the very least you need to be sure to have disconnected the faulty cable leg completely, as the high resistance might be a symptom of all manner of disasters that have happened to it.

 

[DPG]

Is the assessment already booked in?

 

[DefyG]

Hi Luke,

Did you mean 'figure of 8' or end to end? - Shouldn't be in a fig8 configuration.

 

[Pretty Mouth]

Something amiss here, unless I'm having a Friday brainfart (which I could well be, somebody please put me in my place if I am).

Figure of 8, R1+R2=8k ohms at one socket only... 2 points of high resistance, on the cpc either side of the offending socket? But we're getting low Zs at that socket?

 

[DPG]

Something amiss here, unless I'm having a Friday brainfart (which I could well be, somebody please put me in my place if I am).

Figure of 8, R1+R2=8k ohms at one socket only... 2 points of high resistance, on the cpc either side of the offending socket? But we're getting low Zs at that socket?

Agree - can't be right surely? Op, can you clarify your findings. Preferably before much more of this 6.5% beer goes down.

 

[Pretty Mouth]

Agree - can't be right surely? Op, can you clarify your findings. Preferably before much more of this 6.5% beer goes down.

Maybe testing ends of CPCs from different circuits, with high resistance path between them? Can't figure out if that'd give the sort of readings we have here

 

[Jurassic Sparks]

Hidden Junction box with loose connections ?
or some one has moved a socket, but left the old backplate in place and the wires are plastered over and corroding
out with the hammer and chisel and be brave

 

[H]

Had a high reading like this the other week, found it to be a poorly terminated, not tight, cpc where the sleeving has slipped down as to prevent the copper being clamped.

Also had one before where a cpc had come out of the terminal block which gave a high reading.

 

[Pretty Mouth]

If that dodgy socket really was on the ring, to get fig.8 R1+R2=8k ohms would mean 2 much higher resistances on the CPC either side of said socket, being measured in parallel. When measured end to end, those resistances would be in series, so much higher than the measured value, also 8k ohms.

If dodgy socket is a spur, then the point on the ring from which it is spurred must be giving 8k resistance between both legs of ring CPC and the spur CPC. We also have 8k resistance between those legs of the ring CPC. Coincidence that these values are the same? Bit suspect.

If it was me, I'd suspect that I was testing incorrectly. OP, go back and check that you really are testing both ends of that ring CPC, and that dodgy socket really is on that circuit. Do R1+RN fig.8 tests too.

 

[gazdkw82]

For a high end to end on the cpc I'd say the cpc either a loose connection or the cpc has been used to bond many other items, thus creating a much longer and resistive conductor.

Like previously said, the figures on the fig of 8 dont make sense.

 

[static zap]

high end to end on the cpc ... cpc has been used to bond many other items,

Did have that thought its actually Open , but finding a reading through Bonding ,leakage currents !
(if it ever reads the same again)