Shhhh..... exporting tncs and bonding.

[monkey5]

long day...got a metal shed on paving slabs to put 1 double socket and 1 light pendant, its about 1-2m from house. house is TNCS!!

Now do i TT the shed or export the earth. if export the earth do i need to run a separate earth to bond the shed or just bond from socket/light?

wayne

 

[steptoe]

are you really asking this?

headbang

---------- Post Auto-Merged at 23:27 ---------- Previous post was made at 23:27 ----------

its a metal shed FFS

 

[monkey5]

i knew you'd love this steps, only joking mate.

too mnyGuinnessGuinness (well stellas)

 

[steptoe]

monkey,

you know this buddy,

did you really ask this question for someone to try and prove it would be OK to export?

I can understand some folks stance on the wooden shed with no water etc,

but its metal!!!!!!

c'mon, you're not that silly.!

 

[monkey5]

Head clearer this morning mate.your right silly question.so there are such thinks as a silly questions!

 

[m4tty]

Monkey see rod ... Monkey bang rod

 

[Badger]

Whos rod ?

View attachment 1580

 

[batty]

And look what happened to him.

 

[tom1]

let that be a lesson to you all, dont export pme to your roof

 

[batty]

Or get an aerial man in.

 

[mikep]

Let's see where is that book !! think it's called "Earthing your shed by J. R. Steptoe" :slap

 

[magwa the pict]

I always consider it not exporting but bringing within the equipotential zone, but opinions differ.

Pict

 

[steptoe]

I always consider it not exporting but bringing within the equipotential zone, but opinions differ.Pict

wonder what the DNO would say about that?

the other issue we have is this,

please STOP calling TNCS PME, its not the same,

even if the DNO comes round and puts a nice sticker on, its still NOT proper PME,

BTW, I have removed the PME label from my cut out and posted it back to them with a nice little letter explaining the rules on false representation,

 

[magwa the pict]

The DNO have nowt to do with it if I consider it appropriate I can reduce or increase the equipotential zone IE if I have electric heating & propigators in my green house I can have it earth free or within the zone likewise the lathe, mig, compressor in my wooden workshop it all depends on the degree of protection required, for instance given the possible current demand in the workshop it is TT,d where the exporting option gave me a Ze that meant a complicated selection og MBC,s C & D's where by I get well within the disconnection times by TT due to good soggy soil the greenhouse is part of the house tncs as the demand is low, there is no one answer to this as any one who has carried out Agricultural work will tell you, try getting the DNO to expain PNE Not PEN Not PME Not TT but PNE

Pict

 

[apprentice87]

Hi all,

It is "PNB", that so far as i know, stands for "protective neutral bonding" I do not really understand the difference though, but one thing i do know, is that i often read that the DNO has "converted" a supply from TNS to "PME" at the cutout, but as far as i know this is simply not possible without digging up the road outside, as PME, again, so far as i know, requires that there is an additional earth rod at the point where the service cable joins the main..

Here is something i have included from Eon just as a matter of interest:

E2.8.5.1 Provision of LV Earthing Terminal

The provision of a LV earthing terminal has been achieved by various means in the past. The

present company policy with regard to the provision of a LV earth terminal is detailed below :-

PME Terminal (TN-C-S)

All new supplies, or existing customers requesting a load increase, will normally be

offered a PME terminal. However, for reasons of safety some installations are not suitable

for a PME earth terminal in which case a TT supply will be offered (see Section E6.3 for a

detailed list of exceptions). Under the ESQC Regulations, the Company is not obliged to

offer a free PME earth terminal to existing customers that do not already have a PME

earth.

Sheath Earth Terminal (TN-S)

The Company has an ongoing obligation to maintain the integrity of the sheath earth

terminal of customers which already have this type of earthing. If an existing sheath earth

customer requests a service alteration or in the event of a fault repair then the existing

sheath earth must be maintained unless the customer request a PME earth terminal

instead. A sheath earth terminal shall not be made available to new customers (or existing

customers if they do not already have an earth terminal).

PNB Earthing

PNB is a special method of earthing, similar to PME, where the neutral earth is installed at

or adjacent to the customer

 

[steptoe]

Magwa, I think you will find it has a lot to do with the DNO, they have supplied a single building, if you wish to use this to then supply another building/erection you MUST first obtain their permission, which in most circumstances will be granted, subject to missus and normally with the exception of a denial to use the TNCS (or PME) earthing terminal if they have provided one.

If people are going to continue this practice then is it any wonder we are the cowboy trade?

We **** people off continually for sub standard work, then we have a so called tradesman that simply does a cowboy job like taking a TNCS out of the original building and tries to justify it by saying he has extended the EZ,

What justification can you give for this?

Or simply making an install TT because you cant achieve your Zs on TNCS ! WTF! That just smacks of an incompetent cowboy that cant design the system properly!

*******!

 

[magwa the pict]

Hold on till I wind my tounge in from my cheek, and here's your leg back, read my post again and tell me your taking my "suggestions" serious

 

[steptoe]

No worries magwa,

So pray tell where you were taking the proverbial then?

And please remember, these forums are read by unsuspecting members of the general public,

That aside, I dont see anything that wouldn't be generally done by a typical cowboy that doesnt understand earthing systems.

 

[apprentice87]

Hi all,

I personally cannot see the problem with "exporting" TNCS, but only IN CERTAIN CIRCUMSTANCES.

Obviously you could not export it to a tin shed for obvious reasons!! Mind you, i suppose it is not that much different than having the original TNCS supply in a tin shed.

To be honest, TNCS is just a stupid system, and an excuse for the DNO's to avoid maintaining the integrity of their cable sheathing/earthing conductor..

Not sure how you could fail to achieve required Zs on TNCS unless design was errrm, not good!...

Mind you, the supply to my street is rubbish and i have a loop impedance of about .28 on both L/E and L/N [TNCS remember] sooooo, installing large "D Curve" breakers might be a problem and volt drop right at the supply origin is not too clever either.

I have loads that draw 75A a phase. With a loop impedance of .28 that is not good... bad volt drop.... I get a phase to phase PSCC of 1.5KA if i am lucky, so much for the DNO and their 23KA they quote

Makes you wonder why i spent an arm and a leg to get a 50KA mccb to protect the long tails i have. Still, they might reinforce the supply one day, can only live in hope!!!!

john...

 

[steptoe]

I think, but I may be wrong, DNO quote <16kA for a TNCS system