Meter move tns head now tncs. Is it pme.

[andyelectric]

The 3 phase service cut out for my block of 3 flats was recently moved.

The service head used to be tns. The new service head is tncs. This has not been marked up as pme.

My flat has a new 16mm earthing conductor(connection between old MET and new MET) , however the other 2 flats only have their existing 6mm feeds as part of 16mm twin and earth supplies.

Is the 6mm ok(assuming correct by adiabatic and I would be confident of this) or will pme rules apply and require 10mm.

I ask as although I know it was formerly tns, will someone else see tncs and immediately think pme and 10mm.

Please excuse my inexperience, I require no comment on it.

 

[Deleted member 26818]

It most likely PME, if connected to a public network.
The only way really to be sure is to contact your electricity supplier or the DNO for your area.
You could test the Ze, but that would only be an indication.

 

[driverman]

How do know it's PME? You say it's not been marked up. Could it be there is a reason why it has not been marked up?

 

[Deleted member 26818]

He doesn't know, which is I assume why he's posted

 

[andyelectric]

It most likely PME, if connected to a public network.
The only way really to be sure is to contact your electricity supplier or the DNO for your area.
You could test the Ze, but that would only be an indication.

Cheers for the quick reply. So in your opinion would the formerly compliant 6mm earthing conductor suffice?

 

[davesparks]

Ask the DNO what it is first

 

[andyelectric]

Yes, it is correct that I don't know.

The old head was tns on a paper/lead cable. The 6mm earthing conductors to flats 2/3 were ok.

The only change is the new head and approximately 3m of new supply cable.

I can't get my head around that 3 metres of cable making 6mm dangerous and upping the requirement to 10mm.

 

[davesparks]

Yes, it is correct that I don't know.

The old head was tns on a paper/lead cable. The 6mm earthing conductors to flats 2/3 were ok.

The only change is the new head and approximately 3m of new supply cable.

I can't get my head around that 3 metres of cable making 6mm dangerous and upping the requirement to 10mm.

3 metres of extra cable does not make 6mm dangerous!

But if they have made a N-E connection and converted to TNCS then you may need bigger bonding conductors.

 

[Guest55]

we cant go any further till you know whether its tns or tncs im afraid.

and to be honest , if you own the building , and feel certain that the earthing in place is doing the job adequately , then i wouldnt do anything

 

[Deleted member 26818]

He says that it is TN-C-S, just doesn't know whether it's PME.

 

[andyelectric]

Ask the DNO what it is first

Would I actually get a correct answer. They were pretty crap during the whole meter move and I dont have much faith. (SEPD the new distribution arm of SSE)

The cable cut was an old lead sheathed tns supply and when he cut back the cable for jointing it was clear there were three phase cables and the sheath was the earth. The new cable spliced on had a combined neutral/earth.

My feeling is... Although the new head is tncs, the supply is probably not pme but simply the new cable/heads they are using are always tncs. Sorry for sounding woolly.

 

[davesparks]

Would I actually get a correct answer. They were pretty crap during the whole meter move and I dont have much faith. (SEPD the new distribution arm of SSE)

The cable cut was an old lead sheathed tns supply and when he cut back the cable for jointing it was clear there were three phase cables and the sheath was the earth. The new cable spliced on had a combined neutral/earth.

My feeling is... Although the new head is tncs, the supply is probably not pme but simply the new cable/heads they are using are always tncs. Sorry for sounding woolly.

If the new cable is CNE then they must have converted to TNCS.

Only if they used SNE cable could it still be TNS.

Surely this is obvious?

So you need to assess the bonding requirements with respect to the change to TNCS from TNS and decide what is needed.


I have always found SSE to be the most helpful of the various DNOs I have dealt with

 

[andyelectric]

3 metres of extra cable does not make 6mm dangerous!

But if they have made a N-E connection and converted to TNCS then you may need bigger bonding conductors.

Cheers. That concurs with my thoughts. The bonding has already been uprated to 10mm at some point so is not a worry.

 

[davesparks]

Cheers. That concurs with my thoughts. The bonding has already been uprated to 10mm at some point so is not a worry.

But you said the flats have 6mm earths feeding them? So surely the bonding in each flat cannot be more than 6mm?

 

[andyelectric]

If the new cable is CNE then they must have converted to TNCS.

Only if they used SNE cable could it still be TNS.

Surely this is obvious?

So you need to assess the bonding requirements with respect to the change to TNCS from TNS and decide what is needed.


I have always found SSE to be the most helpful of the various DNOs I have dealt with

The only change though is the extrs cable and head. 6mm was previously a compliant earth as it was assumed by the service head as a tns system. How can this suddenly become more dangerous.??

I may not be clear as couple of beers so bear with me.

 

[andyelectric]

But you said the flats have 6mm earths feeding them? So surely the bonding in each flat cannot be more than 6mm?

Sorry, the bonding in my flat(cellar being where old METwas) has been uprated to 10mm. All gas/water to the three flats runs through the cellar. I am unsure if any bonding work has been carried out within the othet flats.