Ring Final Circuit Testing

[Paul_K]

Hi all,

I'm still learning this stuff so go easy!

I've just carried out a ring final circuit test. Having identified both legs of the ring I began testing between both ends of the line conductor, which has given me an infinite reading on the meter. I also got the same result on the cpc. When testing the neutral I get 0.56 ohm..

The answer to me suggests I have an open cpc and neutral on the circuit. Am I on the right path here, or have I missed something?

Thanks in advance!

The tester is a Fluke 1653B

 

[telectrix]

open circuit on L and cpc. rN is 0.56 ohms so you would expect r1 to be the same. if it's T/E cable, 2.5mm, then expect the cpc ( r2 ) to read about 0.9 ohms.

 

[Paul_K]

Thanks Telectrix, it is T+E, just needed to confirm that as I'm not well experienced in the testing yet, even though it appears obvious! :-/

 

[ifindoubtdont]

Have you definitely both ends of the same ring. If neutral is 0.56 ohm then line should be the same, cpc will be 1.67 x line or neutral.

 

[Paul_K]

Hi ifindoubtdont,

Yep, the ring is on the one breaker (32amp).. Both lines removed from the same breaker, and traced right back to the mechanical insulation where their neutrals and cps were confirmed, which were also together in their respective slots in the board! :-/

 

[telectrix]

so it looks like you have bad/broken connections in a socket, JB, or a damaged cable.

 

[Paul_K]

It appears so..... This is going to be a pain! :-/

 

[telectrix]

not necessarily. look at the socket circuit as a whole. estimate an approx. mid point. then use a wander lead to find which leg has the fault/s. then split that leg and repeat untill you have tracked it down.

 

[Paul_K]

Good advice Telectrix, a wander lead is next on the shopping list.. I just got my Fluke T5-600 through the door this morning. I'm thinking I should maybe have got a wander lead first, considering I've got a Fluke i410 clamp & T140 already! :-/

 

[telectrix]

in the absence of a wander lead. just buy a roll of 1.5mm single cable. use that. and deduct the resistance ( about 1.5 ohms or thereabouts) from your readings.

 

[Paul_K]

I'm going to buy one anyway. I need one for testing bonding etc...

I'll put a 20amp breaker in it for now and look at it when I get the chance!

Thanks for your advice, much appreciated!

 

[onions1066]

Just because they are in the same mcb doesn't mean they are the right legs, been to numerous where the ring has been mixed with the immersion. Can you see the cables are he right ones if not I would try the lives to the other mcb's and the Cpcs to the bar and see if this sheds any light on it.

 

[Guest55]

this fault has "diy upgrades" written all over it lol.

 

[Paul_K]

Onions, the two neutrals from the two legs give a reading, it's the line and cpc that doesn't! :-/

 

[Paul_K]

Biff55,

It has been tampered with at some point that's for sure. There's many a tell tale sign at various points in the installation. Metal boxes that are unearthed with metal socket faces!! Broken bonding conductors, unsheathed cpc's at various points..

I even came across a socket outlet hanging next to the outside vent!! ... I'm beginning to suspect the ring has butchered! :-/

 

[ifindoubtdont]

If it's been tampered with assume the worst and 100% test. As onions1066 says while your at the db just quickly test for continuity with the other circuits, you'll be surprised what you find. "Heinz Canned Worms"

 

[Paul_K]

That about sums it up, yeah!

We've only been in the house a year and finding all sorts...

Took down a door standard a few months ago and a mass of wiring came down (grouped), and judging by the shoddy connectors and absence of sheathing on the cpc it would clearly suggest someone had be screwing around with it! .. So much for rating factors when people just pull things apart and shove them together anyway!! :-/

 

[onions1066]

That about sums it up, yeah!

We've only been in the house a year and finding all sorts...

Took down a door standard a few months ago and a mass of wiring came down (grouped), and judging by the shoddy connectors and absence of sheathing on the cpc it would clearly suggest someone had be screwing around with it! .. So much for rating factors when people just pull things apart and shove them together anyway!! :-/

Yes I'm saying you need to check you've got the correct lives and earths just because they are together it doesn't mean they are correct

 

[Paul_K]

Hi Onions1066,

You'll need to bear with me on this, like I said I'm not that experienced yet!

The conductors were all traced back to their respective mechanical insulation,
where the two neutrals were clearly identified from their respective legs, and were followed from that point to the board where they become joined. The same was done with the line and cpc's, which are seen following their line and cpc conductor to their point on the board. All were then disconnected from the board, isolating them completely from all other circuits. This tells me I'm testing between the two disconnected legs, two disconnected legs where there's continuity between the neutrals!! There's no evidence looking at the conductors (as they can clearly be seen coming from the mechanical insulation in which they originate) that they're mixed up!

Hope this makes sense? :-/

 

[Edd]

walk around with your Loop meter find the higest reading, remove socket, find broken conection, reconect it,, jobs done

 

[pete555]

this fault has "diy upgrades" written all over it lol.

sounds familiar reason for part P i suppose even though it,s crap

 

[onions1066]

walk around with your Loop meter find the higest reading, remove socket, find broken conection, reconect it,, jobs done

Yes mate that's right I was saying if you couldn't see them going into the outer sheath. :goofy:

 

[chrish_1977]

What mechanical insulation are your referring to, I would check across all lines and neutrals, had it so many times with lines and cpc's mixed up, doesn't take long and can save you chasing your tail for a fault that is very easy to find, if you check and all ok, then start breaking down the ring.

 

[Paul_K]

The mechanical insulation (mechanical protection) of the flat PVC T+E cable... The gray outer sheath!

 

[FAA Greenie]

I'll tell you how i do it, without the hassle of dragging wander leads all over the gaff.

Remove all the plugs from the sockets in that circuit. connect one leg only of the offending component of the ring, perhaps an earth in your case and then go round with a typical three neon socket tester and find out at which point you go from earth fault to a good reading. Then connect the other end and do the same in the opposite direction - you will narrow down the fault in no time.

If the fault is within an FCU on the ring main, you will also be able to narrow this down too.

Then do the same for your line circuit.

I have used this method loads of time and it is much quicker than pulling the wander lead around.

 

[Paul_K]

I'll tell you how i do it, without the hassle of dragging wander leads all over the gaff.

Remove all the plugs from the sockets in that circuit. connect one leg only of the offending component of the ring, perhaps an earth in your case and then go round with a typical three neon socket tester and find out at which point you go from earth fault to a good reading. Then connect the other end and do the same in the opposite direction - you will narrow down the fault in no time.

If the fault is within an FCU on the ring main, you will also be able to narrow this down too.

Then do the same for your line circuit.

I have used this method loads of time and it is much quicker than pulling the wander lead around.

Hi,

Thanks for that, FAA.

I've already ordered a Kewtech ACC50MTL from ISSWWW, which should be here hopefully tomorrow. Like I say it'll come in handy for testing bonding etc anyway..

I'm with ifindoubtdont's on this too. The whole installation will need testing anyway just by what's been discovered.

1) Shower keeps tripping after about 10 mins (9.5kw) 41.3amp on a 32amp breaker, 6mm conductor. Testing shows 36amp is being drawn, though I may get away with a breaker with larger over current protection.

2) Grouped cables above a door standard, poorly terminated in block connectors (too much of the conductors showing), and the sleeving missing from the cpc's!

3) A double surface box fitted directly in front of an outside vent!!

4) An unused light switch point covered with wallpaper (live conductors behind).

5) Pulled off a splash back in the kitchen and there's another exposed point with live conductors freely sitting with no connectors.. Bizarre!!!

6) A spur taken from an unfused spur supplying kitchen unit lighting!

7) Ring final circuit no longer a ring!....

And that's just sor far!!

So Thursday is going to be a busy day!! :-/

 

[supertoad]

this fault has "diy upgrades" written all over it lol.

yes/yes/yes-what else to find??

 

[Paul_K]

It turned out to be one of the living room sockets that was causing the problem with the ring.. Sorted!

 

[supertoad]

if its one of these jobs worth checking gas/water earth ok/ie; not short ends just stuck under the wallpaper!
have had a lot of them !