Ring final fault.

[Soulsurfer]

Hi I have just looked at a friends place and she asked for a test on the CU as she thought it looked tatty ! It is, ran first ring o.k. Next ring seems to run zig zag fashion up & downstairs and to random outlets like a drunk wired it in ! Problem came when testing end to end I got r1 > 2000 ohms, r2 > 2000 ohms but rn 0.41 ohms obviously not cool, but I also got a beep when the rn test result came up on my fluke 1653B ? Anyone have any idea on the beep ? Didn't get it on the first ring tests at all. Now to go find the issue open circuit on the Line & cpc recently decorated and finished house not looking too good.

 

[amlu]

one ring for whole place? or 2 around? most likely cowboy builders or decorators adding sockets from where ever any nearest cable was available....

disconnect every socket, take reading where each cable goes,
drawing in on a paper and writing down the results helps.
expect plenty of plastered junction boxes, good luck...

 

[Soulsurfer]

Yep there's 2 rings and one radial for an on peak supply to a combi dimplex which is all tubed under conservatory floor, plus random usual radials. As I say first ring looks fine but kitchen, lounge, bedrooms ring nightmare ! Not sure if my new fluke is supposed to be beeping on showing rn result or if all 3 cores are broken ? as feels like a weird back feed kind of fault. can't go ripping down ceilings or anything either. Have belled out each leg socket to socket downstairs so far and all o.k. and connected 1 leg at a time to RCBO to see how many sockets worked on each leg separately and they all seemed o.k. So can't see where a break / open cct would be. No test results in house, last contractor that left a schedule was a Wylex 6 way and E7 cu in Jan 1998 but now we have an 8 way Hager with the odd RCBO and mcb and added odd bits here and there e.g. Pond pump, garden ltd etc... Told her get all tested before you buy a house !

 

[Midwest]

Is the beeping just an audible confirmation of continuity? Some MFT's will not have a audible confirmation (adjustable) above a certain setting, i.e. 2 ohms.

 

[davesparks]

Have you tried reading the manual for the tester? It's always a good idea to learn how the equipment work before using it.
Have you measured the resistance of the fault?
Have you confirmed that the L and E haven't just been mixed up with another cct at the fuseboard?

 

[Soulsurfer]

Hi Dave, sorry mate I meant new to me not brand-new MFT, although will try source a pdf manual online. I have tested the end to end on cct and from looking through messy cu it certainly seems correct cables. Although only had the rn reading other two open cct. I have tried to locate feed legs but only found one at kitchen sockets and haven't found the other ! To enable narrowing down of the fault or where it is. I am very new to testing therefore I am asking silly stuff on here from far more qualified sparks. I was thinking I might have to remove and disconnect each socket I know throughout house on the feed from that rcbo and bell out L-N, L-CPC, N-CPC between each one to next to try find that way ? But am losing train of thought and don't want to spend ages tracing an issue that could be in a ceiling hidden jb that I can't rip house apart to find it. But I'm stressing out thinking there may be an unsafe set up in a friends home. Arghh

 

[davesparks]

I would strongly suggest you learn how your tester works before using it otherwise you are putting yourself on a back foot to start with.
If the resistance is higher than the maximum measurable value on your meter then you either need to select a different range on the meter or use another meter with a higher range.

 

[Richard Burns]

The beep will be a confirmation of continuity as this is the default setting.

If you have powered up the ring with only one leg connected in the RCBO (hopefully ensuring that the other leg is safely insulated) and all the sockets on that circuit are functional then this would indicate that the ring is continuous.

In this case I would be expecting a measurement error on your continuity, e.g are you sure the probes were in full contact with the cores being tested?

Retest the end to end results to confirm your readings, if the readings are still OC then use a long lead from one leg of the ring to each socket on that circuit attempting as far as possible to follow the circuit run and at the point where continuity goes OC then this or the socket before it in the circuit is where the break is located.

Sine your results do not appear to match what is possible it would be a good idea to turn off all other circuits (or at least the other ring and radial) and ensure you do not have, for example, the radial being the other leg of the ring and the actual radial terminated as a ring leg in your MCB (though this would not be possible if there is RCD protection in place).

 

[Soulsurfer]

Thanks guys I'll be up there again tomorrow a.m. So might try and see how far I can get with my R2 wander lead although sockets are throughout house in a hideous run ! As far as I can recall I have like 2-3 sockets fed on one leg in rcbo and when out & other leg in and powered I have almost all sockets connected and live but can't help thinking that some plank might have connected one leg of ring into a radial in the other room so causing a weird set up ? But is that what you mean would take out rcd as imbalance I hope so as it all seems so dangerous and in an ideal world I would knock house apart & rewire entirely !

 

[davesparks]

The beep will be a confirmation of continuity as this is the default setting.

If you have powered up the ring with only one leg connected in the RCBO (hopefully ensuring that the other leg is safely insulated) and all the sockets on that circuit are functional then this would indicate that the ring is continuous.

In this case I would be expecting a measurement error on your continuity, e.g are you sure the probes were in full contact with the cores being tested?

Retest the end to end results to confirm your readings, if the readings are still OC then use a long lead from one leg of the ring to each socket on that circuit attempting as far as possible to follow the circuit run and at the point where continuity goes OC then this or the socket before it in the circuit is where the break is located.

Sine your results do not appear to match what is possible it would be a good idea to turn off all other circuits (or at least the other ring and radial) and ensure you do not have, for example, the radial being the other leg of the ring and the actual radial terminated as a ring leg in your MCB (though this would not be possible if there is RCD protection in place).

We don't know that the ring conductors are open circuit, only that it is greater than 2Kohm. If all loads have been removed then the whole ring will appear to be live despite the high resistance connection.

I think he needs to establish exactly what the resistance of the ring is before proceeding further.

 

[Richard Burns]

As far as I can recall I have 2-3 sockets live when fed on one leg connected in RCBO and when that leg is taken out & other leg connected in and powered I have almost all sockets connected and live

In attempting to translate this statement it sounds like you have different sockets live when you have one leg connected to the RCBO as opposed to the other leg being connected.
If this is the case then check behind what will be hopefully the "last" (most distant) live socket on each leg and you should find the problem in one of those sockets (or in an FCU hidden in a cupboard somewhere between them!)

 

[telectrix]

In attempting to translate this statement it sounds like you have different sockets live when you have one leg connected to the RCBO as opposed to the other leg being connected.
If this is the case then check behind what will be hopefully the "last" (most distant) live socket on each leg and you should find the problem in one of those sockets (or in an FCU hidden in a cupboard somewhere between them!)

or a junction box under the bedroom floor which has just been fitted with £25.sq.m laminate flooring.

 

[Soulsurfer]

Thanks guys, got manual sorted and as correctly mentioned default setting is beep on successful continuity test result & anything more than 2KOhm is an open circuit on the fluke but some other testers I've seen in use go to >999MOhms. Would it matter ?

 

[davesparks]

Thanks guys, got manual sorted and as correctly mentioned default setting is beep on successful continuity test result & anything more than 2KOhm is an open circuit on the fluke but some other testers I've seen in use go to >999MOhms. Would it matter ?

It's not an open circuit, it is a circuit with a resistance greater than the meter is capable of measuring on that setting. It could theoretically be 2K1 and it will still record a result of >2K
Either set the meter to a higher range or use another meter which does have a higher range to establish what the resistance is.

 

[Soulsurfer]

Ok Dave I get what you're saying it's just I was expecting 0.39-0.48 etc and got this, no other ranges just IR so bit of a nightmare that the tester can't do its job properly I guess

 

[davesparks]

Ok Dave I get what you're saying it's just I was expecting 0.39-0.48 etc and got this, no other ranges just IR so bit of a nightmare that the tester can't do its job properly I guess

That tester does have other ranges, you really do need to learn to use it properly. It has various megohm ranges used in its IR testing function.
It is not the tester that can't do its job properly, it was designed for carrying out testing of new installations and periodic inspections and it does this perfectly well. It was not designed for fault finding work!
An analogue IR and continuity tester is the best thing for general fault finding in my opinion (and most electricians I know) with a multimeter also being useful on occasion.