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?

 

[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?

 

[Wilko]

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.

 

[lurch]

Chris..... I understood your post

 

[SparkyChick]

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.

 

[static zap]

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 )

 

[Deleted member 26818]

Thinking the OP needs to sort out the difference between ZE and ZS.

 

[westward10]

I think this has been taken out of proportion, it was quite clear what the OP was getting at.

 

[Deleted account]

I think this has been taken out of proportion, it was quite clear what the OP was getting at.

Totally agree westward10 I think some people have got out of bed on the wrong side today.

 

[Deleted member 26818]

I think this has been taken out of proportion, it was quite clear what the OP was getting at.

Weird.
I wonder if I were to look back at your previous posts, how many would be along the lines of “your not qualified”?
Now we have someone conducting EICRs who doesn’t appear to know the meaning of the term Zs.

 

[Deleted member 26818]

Totally agree westward10 I think some people have got out of bed on the wrong side today.

You really don’t think the OP should learn the difference between Ze and Zs?

 

[Deleted account]

I've looked back over the thread and can find no reference to Chris day giving any definition of Zs or even implying a Zs was carried out.

I'm sure Chris knows exactly what Ze and Zs are.

 

[Deleted member 26818]

I've looked back over the thread and can find no reference to Chris day giving any definition of Zs or even implying a Zs was carried out.

I'm sure Chris knows exactly what Ze and Zs are.

Perhaps some spectacles would be in order?
Your correct, instead of referring to Ze and Zs, he used Ze without bonding connected and Ze with bonding connected.

 

[Deleted account]

Post 7
With the bonding disconnected 3.25Ohms Ze

Is that incorrect?
I still cannot find any mention to Zs.

 

[Deleted member 26818]

I still cannot find any mention to Zs.

Exactly.

 

[Deleted account]

Exactly.

Pleased you agree

 

[Deleted member 26818]

Pleased you agree

The reason there is mention of Zs, is because the OP describes it as being Ze with bonding in place.

 

[Deleted account]

Last input on this thread from me

Post 19 Chris mentions bonding out of interest only.

We all read and interpret things differently. This is my interpretation.

Please agree to disagree.

 

[Deleted member 26818]

Last input on this thread from me

Post 19 Chris mentions bonding out of interest only.

We all read and interpret things differently. This is my interpretation.

Please agree to disagree.

Not 100% sure what you’re going on about or what it is you disagree with.
Simple question: What is the title of this thread.
More complicated question: What if anything do you understand Ze to be?