Please help my head is fried from open earths

[dlt27]

Thanks in advance.
Carried out test on a socket circuit today and found open circuit on cpc’s and lives. Sorted out lives, but earths are driving me crazy. I’ve done all the obvious like connected one earth and then testing sockets etc etc.
In the end after disconnecting everything from earth bar( including main earth, all bonds and all cpc’s ) I was still getting a loop reading at all sockets. Max Zs reading taken was 1.26 ohms).
I can’t for the life of me find out where the sockets are getting a near perfect earth from.
Any info or ideas would be greatly appreciated.

 

[Andy5678]

Thanks in advance.
Carried out test on a socket circuit today and found open circuit on cpc’s and lives. Sorted out lives, but earths are driving me crazy. I’ve done all the obvious like connected one earth and then testing sockets etc etc.
In the end after disconnecting everything from earth bar( including main earth, all bonds and all cpc’s ) I was still getting a loop reading at all sockets. Max Zs reading taken was 1.26 ohms).
I can’t for the life of me find out where the sockets are getting a near perfect earth from.
Any info or ideas would be greatly appreciated.

Are you testing ring continuity? What are you results? Why did you decide to disconnect everything from earth bar? What is the circuit wired in? I have so many more questions on your testing methods as they seem a bit random

 

[ashrow]

I have found open cpc's where some one has drilled direct center of the twin and earth, put a rawl plug in and there you go.
Good luck in finding the break.
Have you donre a insulation resistance test ?
Are the sockets RCD protected as it may be a neutral to earth fault helping those reading

 

[Megawatt]

Thanks in advance.
Carried out test on a socket circuit today and found open circuit on cpc’s and lives. Sorted out lives, but earths are driving me crazy. I’ve done all the obvious like connected one earth and then testing sockets etc etc.
In the end after disconnecting everything from earth bar( including main earth, all bonds and all cpc’s ) I was still getting a loop reading at all sockets. Max Zs reading taken was 1.26 ohms).
I can’t for the life of me find out where the sockets are getting a near perfect earth from.
Any info or ideas would be greatly appreciated.

Dlt21 first off a very good earth is a good thing but you say you have every earth took loose on doth ends. What about the earth under the floors, gas line, water lines etc.

 

[SparkyAndGeorge]

you may be picking up an earth through the fabric of the building

 

[Megawatt]

you may be picking up an earth through the fabric of the building

That’s possible SparkyAndGeorge

 

[dlt27]

Carried out insulation resistance test and got 10M ohm. L and N’s = 0.54 ohms end to end. Protected by 61009 RCBO. Checked polarity etc. Plastic incoming water and copper gas
( disconnected at earth bar)
What I’m confused about is why I’m getting such a good earth and where it’s coming from. It’s a TNS with a supply in and supply out
( presume to next property) from cut out. Thanks again

 

[Andy5678]

What ring continuity did you get on CPC? Is this twin and earth cable?

 

[dlt27]

2.5mm T+E. I took a video, but too large to upload unfortunately. Boiler is wired off socket circuit, but like I said main bonds disconnected from earth bar. Was wondering if getting reading because parallel earth through sockets cpc’s joined to gas pipe via boiler spur and through gas pipe to neighbours gas pipe and back through his earth..if that makes any sense.
Thanks

 

[DPG]

Disconnect boiler earth and retest.

 

[dlt27]

End to End of cpc’s is open circuit. Thanks

 

[richy3333]

And what sort of building/structure is it? What is the RFC serving?

 

[Baddegg]

How old is the property, I’ve had an old one in the past where someone had banged a random earth rod into the bare earth under the floor and run a fly lead from the back of a socket! No idea why and only found by chance when looking for a faulty cable....

 

[dlt27]

It’s an old brick built building.. I was thinking sockets might be connected to earth rod somehow, but wouldn’t expect such a low reading of earth rod....
[automerge]1567108816[/automerge]
Disconnected everything from sockets when tested.

 

[Andy5678]

temporary rewire sections between sockets (on the outside of the walls) leaving existing disconnected, until you get continuity and then narrow down the break. You could use a long lead and just go between CPCs

 

[westward10]

Leave one of the cpcs connected to the earth bar and retest ring continuity to the disconnected one, if you have continuity you have a parallel path. I assume IR tests are clear.

 

[dlt27]

It tests are clear.. Thanks

 

[Highresdis]

Connect one cpc to its live at the board, test for continuity at each socket. Check in the last socket that gives continuity (if unclear how it is wired, check those that have highest continuity reading). If necessary, repeat with the other leg at the board. If no loose connections, it may be faulty between the 2 sockets identified.
Don't worry about the mysteriously good Zs with no cpc connected. It's not as important as the non-continuous cpc.