Which is the DNO earth block? PME

[JD Hogg]

Hi All I would be interested to hear your opinions on this situation:

It's a property which used to have the electricity meter in the middle of the house, the consumer unit is still there and there is still a cut out with a 100A fuse in it, a neutral earth block and a small label that says it is PME. Some time in the past there was a service alteration and now there is an outside meter box with the meter and another cut out. The cable between the cut outs is the original electricity board service cable all made off correctly and in good condition. There is a 6mm earth cable between the two cut outs and the 16mm main earth and 10mm bonds to gas and water all go to the original cut out in the middle of the house.

So the question is should the main earth and gas and water bonds go to the new cut out or is it OK where they are?

 

[Leesparkykent]

Have you carried out the adiabatic equation to see if a 6mm earthing conductor is adequate? In an ideal world for PME/TNC-S the earthing conductor would be a minimum of 10mm. This is the distributors equipment though so they must of deemed it to be adequate. What work are you conducting at this property?

 

[Richard Burns]

Don't you just love the DNO, they can do whatever they want!! That really sounds much more like a DIY move of supply!

Because of the arrangements that are in place it is very clear, presumably, that the supply comes in from outside.
The presence of the NE block at the middle of the house indicates that the cable from outside to inside is not part of the consumer's installation, it is the DNO's supply cable irrespective of the fact that they have provided two cut outs.
Therefore the earthing and bonding are correctly located close to to the origin of the installation and connected to the supply company's earthing arrangement.

The size of that earthing arrangement is odd as said above, however presumably the neutral core of the supply cable is providing the earth up to that point as well, so it should be OK, but there is nothing you can do about it anyway.

 

[Flanders]

Is the pme point at the outside box though not the one inside or is the neutral and earth still linked at the inside point ?

 

[ipf]

Sounds like the authority have just cut the original supply and diverted via the outside meter arrangement. Strange.

What have they done with the original meter arrangement....still in place, bypassed straight from the cut out or what ?

 

[Octopus]

Got any photo's?

 

[JD Hogg]

I don't have any photos, the tails coming from the original cut out now feed the CU and the meter has been moved to the outside meter box. The neutral and earth are still linked at both points.

The work is to change CU so I am wondering whether to allow for running new earth cables back to outside meter box which is 15 metres away and very awkward route.

 

[davesparks]

I have had this exact setup before where the DNO just fitted a red link cutout at the old meter position. That one clearly had the PME terminal at the original position

 

[JD Hogg]

Does anyone know if the DNO would have the answer?

 

[ipf]

Does anyone know if the DNO would have the answer?

One can but ask.

Give 'em a bell.

 

[Richard Burns]

They might have the answer but you would be lucky to find out categorically from them in less than the age of the universe.
Still, worth a try.

From my point of view if the neutral and earth are combined then this is the suppliers cable as it against the ESQCR regulations to have a combined neutral earth in a consumers installation.
8 (4) A consumer shall not combine the neutral and protective functions in a single conductor in his consumer’s installation.