Rather High Ze with all the bonding in place

[chris day]

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?

 

[chris day]

Ok forgive me if this is stupid but what has the bonding to do with Ze?

sometimes with the bonding connected you get parallel paths that artificially lower the Ze, i am well aware that is cheating which is why i disconnected bonding

 

[chris day]

Just out of interest Chris, if the connected bonding had brought the reading down to an acceptable level would you have considered that satisfactory?

No

 

[The Ghost]

Sometimes with the bonding connected you get parallel paths that artificially lower the Ze

OK now this is getting confusing can someone explain to me when doing a Ze what has bonding to do with the price of eggs.

 

[chris day]

OK now this is getting confusing can someone explain to me when doing a Ze what has bonding to do with the price of eggs.

forget the bonding mate i was saying it out of interest can we just get back to the point, the Ze is high with the main bonding disconnected, i assume the DNO will need to be notified and if so are they obliged to repair the Poor earth

 

[The Ghost]

#14

 

[chris day]

#14

why mate?

 

[willy fixit]

A phone call to the DNO will cost nothing just do it!
Oh! and tell us what they say!

 

[Timbo]

A phone call to the DNO will cost nothing just do it!
Oh! and tell us what they say!

Ask them what type of supply they are providing as well.

 

[The Ghost]

why mate?

get back to the point

#14 has already answered "the point"

 

[Risteard]

OK now this is getting confusing can someone explain to me when doing a Ze what has bonding to do with the price of eggs.

You are required to disconnect the Earthing conductor or all main protective bonding conductors from the MET to eradicate parallel paths when conducting a Ze test. This way you are only testing the Earthing conductor through to the means of Earthing and not including main bonding.

 

[The Ghost]

I don't see that eradicating parallel paths just disconnecting the bonding to services. If the main earth is connected to the earth bus-bar in the DB then it is connected to all the earths for each final circuit which in turn will connect for instance through the boiler earth to water and or gas. Or the Electric shower through the earth on that to water again to earth and so on. The only way I can see to definitely remove the chance of parallel paths is to disconnect the main earth from the DB bus-bar. Please tell me if I am wrong, although I hardly need say that!

 

[buzzlightyear]

if that the case ,he should have done that straight away so you don't
get the p/paths .bang on the monie.

 

[KEV 1 N]

Ideally ALL installations should have some thing like this....

....to make testing easier.

 

[Ian1981]

It’s not particularly difficult to disconnect the earthing conductor in a domestic installation unless you have say 3 x 10mm conductors not identifying their function and not obvious to o what they supply/connect to, as is often the case in older installations where the tails are 16mm and the earthing conductor is 10mm.

 

[Pete E]

Sounds like the DNO lead sheath is not providing a good earth path, and if the readings stay the same regardless of protective bonding connected or not, then the gas/water supply pipes are probably plastic and therefore not providing any earth.
Contact the DNO to sort their cable

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?