N1 - N2

[swift2]

Hello everybody, I am in need of some help please. I was testing a ring final circuit end to end readings p1-p2 0.32 n1-n2 open and e1-e2 0.67. Cross link phase and earth come up fine which I expected, however for the neutrals I thought it was a loose hanging somewhere so opened all the faceplates and checked connections, some loose so tightened up. I have then tried n1-n2 again but no luck still open. I have then cross linked phase and neutral to see if I could see any irregularities, but no luck all came within 0.03 of each other which shocked me. I have then proceeded to link Phase and Neutral of one leg at a time to see if I could locate where that leg would end or where the break is, it went all the way through, to the other end, same with the other leg. I have then linked everything back in d/b and opened a socket to see if n1-n2 exists still no luck.
I am wondering is there an easier way to find this without disconnecting each socket and testing where each cable goes to and seeing where I am loosing this connection? Am I missing something really simple here? Looking at this too closely or something. Thank you in advance.

 

[ericmark]

Where you have a good idea as to the cable run some times the loop impedance meter can help find the point where break is with a sudden jump between two close sockets.

However I have a special lead I made for my meter so original measures line - earth and my special measures line - neutral.

With more expensive meters when measuring loop impedance auto measures line - earth and when prospective short circuit current measures line - neutral but mine is a cheap meter.

One of my big points when training my son was if you measure on a regular basis you get to recognise when something is not right but if you only use it on the odd time then you don't get alarm bells ringing where things are wrong.

I love my loop impedance tester it has helped locate many faults but there is no magic formula it's down to experience and that is only gained by using the meter again and again so you know what to expect.

 

[Risteard]

Also you r2 reading (incoming cpc to outgoing cpc) sounds high. This should be around 1.67 times greater than your readings for r1 (phase to phase) and rn (neutral to neutral) for 2.5/1.5 cable (e.g. T&E). So there may be a loose/poor connection there.

I presume it's not an old 2.5/1.0 T&E - your reading is too low for that (unless through parallel paths).

 

[bernardgreen]

Terminate one end of the ring in teminal blocks at the CU Keep the CPC conencted to the earth bar.. Leave the other end of the ring in the MCB and Neutral bar to put 230 volts on Phase and Neutral of the ring.

Go round the ring with a meter of test lamp to find which sockets are live and which are not. If you know the cable route then you will know where the break is.

Or instead of using 230 volts use take the ring out of MCB and Neutral bar and connect a battery to Live and Neutral and test sockets for the voltage from the battery.

 

[Taylortwocities]

Its a slow old process.

Sometimes, the old method of disconnecting everything at the CU and use a wandering lead.
TURN OFF THE MAIN SWITCH
Connect one end to the neutral in a 13A plug. The other end to the neutral conductor one one end of the cable and hop round the ring with your meter on continuity, you'll soon see whereabouts to concentrate your efforts.

 

[Spark123]

I'd stick to dead testing, connecting one end of the ring N-E, leave the other open and go around and measure N-E resistance at each point.
I have one of these http://isswww.co.uk/kewtech-kewcheck-r2 which I can connect my MFT to so I don't need to pull the sockets forward.
You should get a good idea of where the break is.

 

[swift2]

Thank you Ericmark for your response. Your test meter sounds very useful, what make is it if you dont mind me asking and is it easy to modify? Guess I am just going to have to do some fault finding.

Thank you Risteard, e1-e2 reading is higher than expected, I will see if I can find something there too.

Thank you Bernardgreen, I have previously connected L-N one leg at a time and tested but with no luck as readings went all the way around the circuit. I have not tried the live test method.

Thank you Taylortwocities, could you confirm if I have this right, Isolate, and then disconnect the legs. Put a metre or so of single cable on to a 13 amp plug socket, take the neutral conductor of a leg so n1 in a connector block with some more single cable and test between them for continuity at each point?

Thank you Spark123, I do have the kewcheck, I have a 1553 and find the probes I have dont always make good connection with it, however I dont mind opening the face plates if I have to.

Thank you all for your time and knowledge and sharing this with me, I appreciate it alot. I think I was looking for an answer maybe a common fault in this situation, however each job is different. I have a feeling it will be a junction box under the fooorboards somewhere. I do know there isnt any continuity between any other neutral conductors of any other circuits. Thank you all again for your knowledge and time.
I will post the problem in the thread once I have found it, I am going to find and rectify it!

 

[Adam_151]

I generally find a mix of what has been presented by Eric and Bernard works well...

The disconnecting of one half at a time to identify which sockets are on which side of the break, followed by a high current loop test between live neutral at the sockets to identify which is the 'last' one on each half of the broken circuit. You then know which sockets the break is between.

I cant quite remember what you do for a line - neutral test on the megger MFTs, but remember it being straight forward.