Work on TN installations come "the 18th" - separate issue

[JohnW2]

If the block was on a PME/TNCS supply, then where does the network PEN split off into N and E for the customer, is there a central point within the building with N and E distributed to each flat, or does each flat have their own cut out?

I don't know for sure, but would imagine that each flat would have its own cutout - or, at least, some equivalent - with the E for the flat splitting from the N there. If that were the case, the addition of a local earth rod connection (to the building's incoming N) would not affect the situation as viewed from a flat - that 'additional', fairly local, earth rod would just be another "M" of the supply's PME.

Kind Regards, John

 

[ban-all-sheds]

I don't know for sure, but would imagine that each flat would have its own cutout

Where?

- or, at least, some equivalent - with the E for the flat splitting from the N there. If that were the case, the addition of a local earth rod connection (to the building's incoming N) would not affect the situation as viewed from a flat - that 'additional', fairly local, earth rod would just be another "M" of the supply's PME.

But what if it wasn't done that way, but was done, as suggested, by a rod connected somehow to the flat's MET?

 

[JohnW2]

I don't know where the 'cutout' would be, but I presume that, to be complaint, the place where (if TN-C-S) the flat's earth split off from the CNE would have to be in, or very close to, the flat. As for "what if it were done by a rod connected somehow to the flat's MET", that is surely what the draft reg (per DPC) is calling for, and is surely what we are discussing here (per the OP of this thread) as being pretty impractical, particularly for a flat which is umpteen floors above ground level, isn't it?

 

[ban-all-sheds]

The DPC made no concessions to practicality.

 

[JohnW2]

Exactly - so, as I said, if/when that regulation comes into force with it's DPC wording, I think that some tweaking will be required to make it workable in the sort of situations being discussed here.

 

[ban-all-sheds]

It seems odd that not one of t'committee thought "hang on, what about tower blocks" when they were discussing it.

 

[EFLImpudence]

As the regulation states "there shall be an earth electrode, supplementing any earthing facility provided by the distributor" I fail to see why more than one electrode connected at the incoming supply of a block of flats would be required.

Where is the earth provided by the distributor?

 

[JohnW2]

As the regulation states "there shall be an earth electrode, supplementing any earthing facility provided by the distributor" I fail to see why more than one electrode connected at the incoming supply of a block of flats would be required.

Indeed - that's essentially what I have been suggesting.

However, even if (as I think should be the case), there would only be one additional earth electrode 'per building', the question still arises as to who is going to install (and pay for) it. If not forced to by legislation (which, as I've said, could take years, and lots of argument, to implement), DNOs are unlikely to be prepared to do it (at their cost), so it's would presumably be down to either the landlord/freeholder or the first flat occupant who wants work done on their electrical installation.

Kind Regards, John

 

[EFLImpudence]

I would say whoever is responsible for the block's internal wiring - BNO.

If it becomes a regulation then they should presumably fit an electrode at the earliest opportunity.


Edit - If

 

[JohnW2]

I would say whoever is responsible for the block's internal wiring - BNO. It it becomes a regulation then they should presumably fit an electrode at the earliest opportunity.

I suppose that would come down to a discussion about whether or not it was 'retrospective'.

Kind Regards, John

 

[flameport]

is there a central point within the building with N and E distributed to each flat, or does each flat have their own cut out?

Can be either, although typically it's a single cabinet at the intake with all the fuses for the individual flats, cables from there to each flat.
If the meters are located in the flats, a cutout with solid link (usually red in colour) is fitted at each flat for local isolation.

 

[SimonH2]

I think you'll find it varies a lot more than that. OK, "my" block is only 4 flats on 2 floors, but it has FOUR separate DNO cables coming into a meter cupboard in the communal hallway, connected to 4 individual cutouts.
As to who pays, well the freeholder never pays for anything. It's normal in leaseholds that the freeholder is responsible for various things (maintaining the common areas and the structure of the building) but the costs are passed onto the leaseholders - with a markup typically. It's one of the downsides of leasehold - the freeholder is in a position to determine that certain expensive works are needed, and the freeholders have (in practical terms) little option but to pay their share.
And then there are the practical considerations. How much work (and disruption and consequent making good cost) is involved in getting from something akin to an MET for the building to somewhere suitable for a sufficiently large earth rod. And what will the specs be for such a shared earth rod ? In the office building I used to work in, the meter room was in the middle of the building (not in itself an issue), but had 2off 3P supplies (from the same substation across the road) into 10 way DNO fuse panels - 300A/phase main fuses, 100A/unit supply fuses (all 1P supplies). So what would the requirement be for a useful earth rod for that lot ?