disappearing earth

[Gaz Bryan]

Just started with the continuity test on a domestic installation prior to a board change. Its only a small property and all the sockets are on one ring cct, a grand total of 10 sockets. I did the phase and neutral and they both came in at about 0.5 ohm but the cpc was open circuit. I've followed it all around the house and the break appears to be between the kitchen and the rest of the house. The problem is that the (i suspect ) dodgy junction box is in the kitchen ceiling. The kitchen is an extension on the back of the house and has its own pitched slate roof, with no access to the ceiling void.
The question is do I investigate further or just bite the bullet and split the ring into two radials?
I have I/R'ed the cpc and it gives a reading of 0.01Mohms at 10v ( i'm using a fluke 1651b).
Any thoughts anyone?

 

[poirot]

0.01mohms at 10v? Do you know at which two sockets the faulty leg of the ring is between?

 

[Gaz Bryan]

Yes it appears to be between the first socket in the kitchen and the last socket in the front room, if that makes sense. The ring goes from the board into the front room where there are four sockets with legs upto one socket in each of the two bedrooms then back into the kitchen to four sockets and back to the board.
the problem is that I cant find where the ring enters the kitchen. Ive had the floor boards up in the bedroom and all the cables are intact before they disappear through a small hole in the wall and into the kitchen ceiling void.

 

[gamblor6]

simple answer is if you cant find the break you need to split the ring gaz

 

[poirot]

Why would there be a junction box in the ceiling void? Are all the sockets in the kitchen on the ring or are there some spurs.

 

[Gaz Bryan]

There are no spurs, the junction box in the ceiling void is the only thing i could come up with for the readings. It's just me clutching at straws.

 

[eckersecker]

IOs there a kitchen cupboard screwed through cable. Had similar with wall mounted horsebrass going through cable.

 

[eckersecker]

Sorry, not IOs , but Is.

 

[Amp David]

Sound like when they built the extension, they may have added this to the existing ring and like the OP said, used a JB somewhere to join it.

If you are sure its in the ceiling void, explain to the customer the pros and cons of splitting and making 2 radials and knocking a hole in the ceiling to fix.

 

[Octopus]

Does the CU have capacity for an extra fuse/mcb allowing you to split the circuit? If not would it be acceptable to add a CPC link from the "2" offending sockets so that the CPC is then a "ring"?

 

[spsparks]

get a dade, a 110mm cutter and cut a hole in ceiling above the suspect sockets. Rattle the cables to get an idea of where the joint might be.........after you find/sort it. Fit a batten across the hole then screw back the cutout and fill the gaps............my customers love this one and it leaves the job sorted and i find the joint after about 4 holes ............usually.

 

[acvc]

I'd opt with a JB and not a damaged cable, as CPC is in middle of cable - a screw through it would probably still offer some continuity reading and prob reduce IR readings.

Classic case of why all terminations and connections should be accessible at all times I suppose.

If you're going to run a CPC single between the two sockets then you might as well run a full 6242Y. The damage won't be much different.

Two rads: test results, loads on each rad, and space in c/u permitting

 

[poirot]

I had a fault on a existing ring main, i installed an extra socket and found there was no continuity on the cpcs when testing. Located the faulty wire to be between two sockets in the lounge, found a jb with a spur but all connections were ok, after a bit of head scratching the break was found to be caused by a nail in the skirting board! i have to add the original nail from when the house was built 40yrs ago. It was worrying that this fault had never been picked up in 40 yrs, just goes to show the importance of testing every circuit you work on.

 

[kung]

I know its changing the focus here but get yourself one of them snake scopes ! makes life so much easier buddy ! Maplin do them cheap.

 

[Octopus]

Kung, what type of snake scope do you have? Is it one that needs a laptop to operate?