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Carrying out an EICR on a property in london, the supply is a TN-S supply with an incorrect tenby earth clamped around the PILC Sub mains cable.
Long lead tested all the main bonds and i am very surprised to still get such a high reading with these parallel paths in place.
3.25ohms
With the bonding disconnected 3.25 which remains relatively the same with the bonding connected again

Would i be correct in saying the DNO will need to be notified and called out?
 
Last edited:
If there was an issue with the earth coming from the DNO lead sheath, what would the DNO do, convert the supply to TN-C-S or is it more complex for them than that?
Hi Pete - if the DNO provide the means of earthing to an installation then they will maintain it if asked. But reading the thread it's not clear to me if it's genuinely DNO or some historic home brew. Anyway, DNO may choose to convert to PME and they will consult their records / inspect their local infrastructure to see its set up ready for it.
 
If there was an issue with the earth coming from the DNO lead sheath, what would the DNO do, convert the supply to TN-C-S or is it more complex for them than that?

The last TNS installation I worked on with a bad earth, I advised the client to contact WPD and have them sort it.

Their official line was "we don't support TNS anymore". The engineers went to the client site, test the earth and concluded it was garbage and advised that I move the bonding clamp up the cable (it was a normal bonding clamp on the armour/pitch outer sheath) to the lead just below the service head or fit a rod.

I have no idea of the history of the earth for the property, but as far as they were concerned, it wasn't really their problem.
 
Ideally ALL installations should have some thing like this....
View attachment 40139
....to make testing easier.

Tricky -too neat a solution .
( If some one has to un-do / leave another wire dangling/cut a wire )
"To clear a problem".
They are more inclined to feel-doing it WRONG..
( "THEY" --- Usually own a pair of spurs )
 

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