Ring Main Tripping Rcd And Connected With Main Earth

[Lucien Nunes]

Hang on a minute. 1.4kΩ ring L to MET? That's a big fault! At 230V it would dissipate 230²/1400=38W i.e. the heat of a largish soldering iron and hence probably show itself pretty soon (a carbonised rat will only function as a heating element for so long before either crumbling apart or setting fire to the house). Alternatively it is a mis-connected load that is running to earth instead of neutral but surely then the RCD would have tripped immediately it was connected.

I'm assuming the neutrals were disconnected at the CU when you did this test of course? Otherwise a normal load still plugged in somewhere will show a reading to E as well as N via the supply.

Is the IR fail at each faulty leg the same resistance? If so, then it does sound like one fault with multiple legs incestuously interconnected to it. If not, then I think Mr Rat will have had a hand (or tooth) in creating this problem, as he is known to enjoy sampling multiple cables in a single installation in search of the tastiest.

 

[captaincaveman]

Hang on a minute. 1.4kΩ ring L to MET? That's a big fault! At 230V it would dissipate 230²/1400=38W i.e. the heat of a largish soldering iron and hence probably show itself pretty soon (a carbonised rat will only function as a heating element for so long before either crumbling apart or setting fire to the house). Alternatively it is a mis-connected load that is running to earth instead of neutral but surely then the RCD would have tripped immediately it was connected.

I'm assuming the neutrals were disconnected at the CU when you did this test of course? Otherwise a normal load still plugged in somewhere will show a reading to E as well as N via the supply.

Is the IR fail at each faulty leg the same resistance? If so, then it does sound like one fault with multiple legs incestuously interconnected to it. If not, then I think Mr Rat will have had a hand (or tooth) in creating this problem, as he is known to enjoy sampling multiple cables in a single installation in search of the tastiest.

I haven't tested the system energised as she said there were a lot of sparks/bangs when one of the previous elecs tried it. when I tested continuity from ring live to main earth i did it directly from the ring live to distributers earth with EVERYTHING disconnected including bonding. Like I say, This would suggest to me the live is earthing via pipework? At first I thought the fault lay where the cables entered the metal corroded ccu through an unprotected hole but on closer inspection the damage was superficial (& yes I protected the hole afterwards - BTW, where can you get hole protecting rubber/open grommet as i couldn't source any?)

What confuses me is there is only 1 ring (which runs along the upstairs as it is concrete downstairs). Now, if that is spurred why has that downstairs socket got two legs rather than just the one? It must be in a ring then but with multiple faults. Maybe Mr Rat is indeed...

 

[Richard Burns]

Cats have been known to pee on sockets as marking and so get them wet and fail IR tests, especially if they are uncontrolled male cats. Maintaining an IR test running and seeing if the value increases may be an indication of "water" on the circuit!

A ring on one floor can often be wired up and down as required so your layout could be something like this.
However there are various different wiring methods dependent on the age of the wiring that could produce different results, however having two cable at each socket tends to indicate this more normal arrangement.
However unfortunately this is only one possible option and it has been known! for people to wire things fairly unconventionally or illogically.

A resistance to supply earth from an unconnected line conductor does seem to indicate a connection to earth but this coudl be from a damp house with a the line touching the wall or a metal pipe or any number of other possibilities, probably best to stay with the circuit itself at first, as a connection to a cpc in the circuit that is supplementary bonded in the bathroom for instance would give the same result.

 

[captaincaveman]

Cats have been known to pee on sockets as marking and so get them wet and fail IR tests, especially if they are uncontrolled male cats. Maintaining an IR test running and seeing if the value increases may be an indication of "water" on the circuit!

A ring on one floor can often be wired up and down as required so your layout could be something like this.
However there are various different wiring methods dependent on the age of the wiring that could produce different results, however having two cable at each socket tends to indicate this more normal arrangement.
However unfortunately this is only one possible option and it has been known! for people to wire things fairly unconventionally or illogically.
View attachment 33200
A resistance to supply earth from an unconnected line conductor does seem to indicate a connection to earth but this coudl be from a damp house with a the line touching the wall or a metal pipe or any number of other possibilities, probably best to stay with the circuit itself at first, as a connection to a cpc in the circuit that is supplementary bonded in the bathroom for instance would give the same result.

Thank you very much for your time Mr Burns. Appreciated! I did a simular plan (Above) but not nearly as smart. The blue is where I think the fault lies according to my readings. If I get access to the sockets I will have a better idea. One thing that doesn't make sense on my plan is I'm sure socket 4 had one good & one bad leg. I had to lean over a table to check it before so if it's cleared now I'll have to check it again. It wouldn't suprise me at all if the cats or dog was to blame. Also there is a lot of moisture in the air (due to urine and no windows open) so you could be right with the line to earth thing

 

[marconi]

'No problem can withstand the assault of sustained thinking' [Voltaire]

 

[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