no cpc continuity on ring final, strange readings !

[Rockomuir]

Good Evening all,

Been at a property today starting intial tests for a board change tommorow. There are two ring circuits, on one of the ring circuits i had an open circuit on the cpc. Live and neutral where fine 0.4/0.4. I started to locate the break by splitting the legs and joining the live and cpc going from socket to socket. After a few sockets i thought i had located the the area where the problem was as i had no continuity. However after i decided to test a few more sockets as they were close by and instead of getting an open circuit reading i got a reading of 300ohms. This throw me a little so i went back to board and checked the other ring cicuit which tested out fine 0.5/0.5/0.8. I then checked the cpc of the leg from the first ring and a leg of the different ring and got continuity which makes me think that there is a link somewhere.

It is a tncs and there is an fused spur for a pond pump which i cannot get at until tommorow due to a wardrobe in the way.

Has anyone got any suggestions for the reading of 300ohms, and other suggestions for fault finding this problem. I have taken 90% of the faces off and even though i found one slighlty loose connection it did not clear the fault.

 

[GLENNSPARK]

good evening all,

been at a property today starting intial tests for a board change tommorow. There are two ring circuits, on one of the ring circuits i had an open circuit on the cpc. Live and neutral where fine 0.4/0.4. i started to locate the break by splitting the legs and joining the live and cpc going from socket to socket. After a few sockets i thought i had located the the area where the problem was as i had no continuity. However after i decided to test a few more sockets as they were close by and instead of getting an open circuit reading i got a reading of 300ohms. This throw me a little so i went back to board and checked the other ring cicuit which tested out fine 0.5/0.5/0.8. I then checked the cpc of the leg from the first ring and a leg of the different ring and got continuity which makes me think that there is a link somewhere.

It is a tncs and there is an fused spur for a pond pump which i cannot get at until tommorow due to a wardrobe in the way.

Has anyone got any suggestions for the reading of 300ohms, and other suggestions for fault finding this problem. I have taken 90% of the faces off and even though i found one slighlty loose connection it did not clear the fault.

wander lead (method 2) would have been better here...

 

[Octopus]

300 ohms is probably a very long way round through items connected..... Do you have all the connections for this ring disconnected at the board?

 

[GLENNSPARK]

disconnect the CPC from both rings....and start to narrow it down to the point where the 300 ohm continuity between em is....

it could be that when the cables were pulled in originally the holes through the joists were too small and hence overpopulated....causing the cables sheething to `burn`...and thus creating a semi conductive path between CPCs...

just a thought mind...

 

[Rockomuir]

Yes all connections removed from board. But you have made me question if I had left the neutral connected at some point. Would hit be a possible explanation fo the 300 ohms

 

[GLENNSPARK]

Yes all connections removed from board. But you have made me question if I had left the neutral connected at some point. Would hit be a possible explanation fo the 300 ohms

no.....

 

[Rockomuir]

Thank you for that, I will start again tommorrow with a clear head and a fully charged tester

 

[GLENNSPARK]

whats IR like?...everything clear?

if so then does every point served have R2?...
if so then do the adiabatic for time/current...

note r2 is not continuous on the cert... but that theres R2 available at each point...

 

[telectrix]

maybe. strange things happen with neutrals.

 

[GLENNSPARK]

you dont fail it just for the CPC not being a ring....

if you do the adiabatic...prove its good for time current (i assume its a 30-32A OPD?)...
then go round the points served...as long as R2 is there...and the adiabatic comes back OK....
then note that r2 is not continuous....
thats all really...

 

[GLENNSPARK]

maybe. strange things happen with neutrals.

well he needs to zap it to prove electrical seperation...

 

[Des 56]

300 ohms cpc to other circuit cpc !

Multiple items on both rings left plugged in,or flexed connections still atached,cpc continuity between the rings provided by pipes between the fitted appliances

There again,maybe a slack screw or such

 

[Rockomuir]

There might be a few things plugged in like the pond pump and a spur for an outside light which until the client moves the massive wardrobe I cannot check. ir test came in okay

 

[Octopus]

There might be a few things plugged in like the pond pump and a spur for an outside light which until the client moves the massive wardrobe I cannot check. ir test came in okay

SO if your IR is OK then nothing is plugged in - that is if you've IR'ed all 3 cores to each other!

 

[onions1066]

Slack screw is most common. If I get a dodgy reading first thing I do is tap all the sockets if the reading changes you've got a loosey. Tighten it up bobs your uncle. Sack off all that time consuming splitting the ring when there is no need. Other than that agree with glen get the wonder lead out.

 

[GLENNSPARK]

Slack screw is most common. If I get a dodgy reading first thing I do is tap all the sockets if the reading changes you've got a loosey. Tighten it up bobs your uncle. Sack off all that time consuming splitting the ring when there is no need. Other than that agree with glen get the wonder lead out.

best done with an anologue instrument on an end to end....

 

[Guitarist]

you dont fail it just for the CPC not being a ring....

if you do the adiabatic...prove its good for time current (i assume its a 30-32A OPD?)...
then go round the points served...as long as R2 is there...and the adiabatic comes back OK....
then note that r2 is not continuous....
thats all really...

My issue with that solution is that there could be other more dangerous issues about to rear their ugly head. If the lack of cpc continuity is the result of a damaged cable, then their could potentially be sheathing or insulation damage.
Personally, I'd want to find out.

 

[GLENNSPARK]

My issue with that solution is that there could be other more dangerous issues about to rear their ugly head. If the lack of cpc continuity is the result of a damaged cable, then their could potentially be sheathing or insulation damage.
Personally, I'd want to find out.

hence my posts at #4, #8 & #11

 

[onions1066]

best done with an anologue instrument on an end to end....

The trusty robin analogue for me

 

[rattlehead85]

Best way and clearest way to pinpoint the problem would be to firstly liven up the ring affected only and note which sockets are live. Then disconnect one of the legs at the board and split the cables at each socket. Liven up the ring and go socket by socket with a voltage indicator between line and earth. Connect each socket back one by one until you reach the leg that fails to give you 230v between line and cpc. The leg that fails to give you this is the fly in the ointment job done!!
Just hope the one down isn't a pig to rewire or repair!!