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?

 

[buzzlightyear]

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.

Would i be correct in saying the DNO will need to be notified and called out

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[westward10]

What was it then, the Ze.

 

[chris day]

What was it then, the Ze.

3.25Ohms

 

[chris day]

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3.25Ohms sorry that was quite an important detail

 

[Octopus]

What was the Ze with the bonding disconnected?

 

[chris day]

What was the Ze with the bonding disconnected?

With the bonding disconnected 3.25Ze which remains relatively the same with the bonding connected again

 

[The Ghost]

You do mean main earth for Ze?

 

[chris day]

You do mean main earth for Ze?

Yes

 

[The Ghost]

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

 

[KEV 1 N]

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

 

[KEV 1 N]

What was the PFC? Was the reading better between L and N?

 

[Pete999]

Was the main Earth dissed from the CU when you tested Ze why mess with the Main bonding? after all you are testing the earth fault impedance with the main earth dissed. aren't you?

Yes he is testing 3 Phase but the principle is the same for SP&N

 

[The Ghost]

Yes but let's assume the Ze is/was 3.25 Ohms fine, however whether I connect the bonding or not this will make not a jot of difference. It is somewhat confusing the description of the scenario. In any event if the external impedance is that high, then yes of course the DNO must rectify it. However they could say there is no earth someone put that BS953 clamp on and it's nothing to do with us we only have to maintain an earth we supply. In which case it's tough TT for you.

 

[Deleted member 9648]

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