Ring Main Tripping Rcd And Connected With Main Earth

[captaincaveman]

Hi you beautiful people.
Just been looking at a rather confusing and disgusting job in a two floor ex-council house and wondering if anyone could give me any ideas (apart from walking away from it).

• The ring has been tripping the RCD (main switch)
• Live and Neutral have both failed IR test to earth
  
• I split the ring at 4 sockets starting at furthest point to try and locate the fault but each socket is showing 1 leg of ring to be ok & 1 leg to fail IR test. This would suggest to me they are all on radials from a single point then spuring off to downstairs from each socket or there are multiple failures?
• I tried to trace the cables using a circuit finder but the device kept strobing to show live (or as i believe to show it's looping). I did a continuity test between ring live and main earth with everything disconnected (TNS) and got a reading of 1.4Kohms. If there is any continuity between live and earth on a tns does this mean the ring is touching the water pipes and going outside for a walk?
• I managed to have a look under the bathroom floor to find one leg which seemed ok at that point. Other sources of water I'm thinking of are radiators, boiler (out of use) and pet urine.

I had to leave the property until the customer cleared the rooms of junk, poo and urine so i could get in them before I could do any more. A lovely lady but she thinks she's a witch with a dozen cats, dog and crow (and lots of flies). Apparently 13 electricians walked away so half of you probably know where i'm talking about lol.

 

[Richard Burns]

If that is how you think the ring is faulty then run a cable from socket two to socket five and disconnect the potentially faulty legs. The ring should then test as a no fault ring and if you do a full ring test then you can ensure that other sockets suspected to be OK are in fact on this reduced ring.

Then you can concentrate your fault finding on the suspect cables and ignore the rest.

 

[marconi]

BTW, where can you get hole protecting rubber/open grommet as i couldn't source any?)

Try: https://www.tlc-direct.co.uk/tcl/search?query=grommets&Submit=Search

 

[Dan]

Try: https://www.tlc-direct.co.uk/tcl/search?query=grommets&Submit=Search

Or our forum sponsors www.cef.co.uk who gives a discount for forum members.

 

[Lucien Nunes]

Also there is a lot of moisture in the air (due to urine and no windows open)

Moisture alone will not give you a reading of 1.4kΩ unless the whole circuit is underwater. 1.4MΩ yes, but not 1.4kΩ. If that reading is correct, then there must be some other mechanism, such as a 'contaminated' fitting that has tracked, carbonised and is now a charred heap of stuff instead of a plastic accessory. You mention sparks and bangs - where from? If from the DB, then probably the MCB was reacting to a hard short and the 1.4k is what's left now the fault has burnt itself out. One way or another it ought to be visible when you reach it.

 

[captaincaveman]

Try: https://www.tlc-direct.co.uk/tcl/search?query=grommets&Submit=Search

Ah! It's called grommet strip! Was wondering lol. sweet cheers

 

[captaincaveman]

I've kinda sorted it. Now able to get into bedroom 1, I found the insulation fault between sockets 3 & 4. It was in the stretch between socket 4 and about a foot under the floor. I was unable to see any reasons (nails, backbox hole rubbing etc) suggesting a breakdown within the cable so I just cut both legs below the floor, joined them and bypassed the socket. THEN, I found another fault on the same circuit in the kitchen between new found socket (opposite to socket 6) and the ccu. As I couldn't get into bedroom 3 to locate the fault I split the ring at that point, did all the testing which was good, downgraded the MCB and made the ring into a radial. I suggested she call me when she's cleared the room.

I actually also found an earth fault to the fluorescent in the kitchen but thats another story..
I also told her she could do with a rewire... and a tidy up...

 

[Richard Burns]

Well done, good progress, and thanks for letting us know what's happening.