Earthing Arrangement- confused

[steptoe]

It's certainly done that way in the U.S. The NEC requires an earth electrode connected to the neutral at the service entrance.problem, its TNS , not PME,

What is unsafe about having an extra earth electrode on a TN-S or TN-C-S system?

two massively differently systems, dont you even understand the differences in them, let alone TT.?

How is it any different - electrically speaking - from a house which still has a metallic water supply line running multiple tens of feet below ground, and which is required to be bonded?

dont the regs now specifically state you are not allowed such earthing systems?

I wouldn't call changing from TN to TT an upgrade, but still......

you obviously have no conception about earthing systems

And who would be the last person to touch the system? The DNO, surely?

NO, the installation is nothing to do with DNO, he disconnects at the cut out

Should any DNO guy be casually disconnecting a TN earth just because he happens to see an earth rod connected to the MET?

DNO are NOT obliged to provide you with an earth

Steptoe,I'm new to the forum, and have read several posts you have made on the merits of various earthing systems.

I don't want to get into a debate about the merits etc.

However, just a question as to how you feel it is possible for a DNO to unilaterally change a supply system, and also not comply with the ESQCR?

Surely they would be in breach of their statutory duty?

IF the DNO provide the earth via TNS/TNCS then they are then legally obliged under ESQCR to maintain it?

they can withdraw this at any time, and as you are providing your own earth they may do so

Are there that many examples of the failure of DNO TNCS systems that you have experienced.

YES

Please excluding the extremely rural borderline TNCS systems that are around, where probably TT would undoubtedly be better suited.

I had a walk around my little village recently with one of our local DNO guys and we counted about 6 earthing rods apart from the local transformer (HV&LV) and the local underground stake on the other LV supply.

He also put in for another 3 or 4 that day, and this is a hamlet of less than 30 houses on the outskirts of a major city.

BTW my house is irrelevant I'm TT!

Paul

harks back to fast track,

prople need to start understanding the fundamentals of earthing systems and the inherent dangers that can be induced by getting the basics wrong.

posts like these should really be in the students section when such things are basic.

 

[netblindpaul]

steptoe,

I'm NOT a fast track!

I was merely trying to get an idea of the reasoning behind your posts.

I did not mention the removal of DNO earthing after a rod had been fitted.

You inserted that into my quote without my having any referecne to this situation.

IF the DNO supply an earthing facility then they cannot withdraw this unilaterally under ESQCR now can they? (faults excluded)

I did not suggest that multiple (mixed) supply systems was a good idea.

I don't believe that it is.

I do have a good fundemental understanding of systems design and I do understand the "merits" of the various systems.

My question was and still is how you feel that a DNO can unilaterally change the supply system and disconnect means of earthing (faults excluded).

As far as I understand most DNO's now have robust fault monitoring systems.

Also, under EAWR, Building Reg's etc. the responsibility of the installation electrican cannot be taken past the DNO cut out.

As long as the fixed install is completed in accordance with the supply system in the facility and complies with 7671 & "building regs" then I fail to see a case for civil or statutory negligence on an installation electrician for failures within the DNO system which is out of their control, and covered by a different set of actually statutory legislation which 7671 is not.

Paul

p.s. it's been a long time since I was an apprentice, but not so long since I have been in education as I believe in lifelong learning.

 

[PBC_1966]

problem, its TNS , not PME,

Why is an earth electrode at the service entrance a problem with either system?

two massively differently systems, dont you even understand the differences in them, let alone TT.?

Yes, I'm well aware of the differences between all three systems. But why do you think an earth electrode as the customer's premises is somehow unsafe with either TN-S or TN-C-S/PME?

With either system there is likely to be an additional earth path by way of bonded pipework, structural metalwork, etc.

How is it any different - electrically speaking - from a house which still has a metallic water supply line running multiple tens of feet below ground, and which is required to be bonded?

dont the regs now specifically state you are not allowed such earthing systems?

They don't allow a water-pipe electrode as the earthing means for TT, and have not done so for years. But that's not what we're talking about.

You're arguing that it's somehow unsafe to add an extra earth electrode with a TN system. I'm pointing out that it's a requirement to bond metallic pipework (as you have stated yourself in another thread that you would always do), and that therefore if that metallic pipework is already effectively an earth electrode it's electrically no different.

I wouldn't call changing from TN to TT an upgrade, but still......

you obviously have no conception about earthing systems

Why do you consider TT to be superior? Are you aware that in many places TT is actually prohibited?

DNO are NOT obliged to provide you with an earth

True. But in the case under examination they have already provided one. They can't just come along and disconnect it without regard for the safety of the installation.

If you had a TN-S system without any extra earth electrode at the premises (intentional or incidental by way of bonded pipes etc.), do you think the DNO could just cut the earthing conductor without bothering to tell you?

 

[steptoe]

steptoe,I'm NOT a fast track!

I was merely trying to get an idea of the reasoning behind your posts.

I did not mention the removal of DNO earthing after a rod had been fitted.

You inserted that into my quote without my having any referecne to this situation.

IF the DNO supply an earthing facility then they cannot withdraw this unilaterally under ESQCR now can they? (faults excluded)

I did not suggest that multiple (mixed) supply systems was a good idea.

I don't believe that it is.

I do have a good fundemental understanding of systems design and I do understand the "merits" of the various systems.

My question was and still is how you feel that a DNO can unilaterally change the supply system and disconnect means of earthing (faults excluded).

As far as I understand most DNO's now have robust fault monitoring systems.

Also, under EAWR, Building Reg's etc. the responsibility of the installation electrican cannot be taken past the DNO cut out.

As long as the fixed install is completed in accordance with the supply system in the facility and complies with 7671 & "building regs" then I fail to see a case for civil or statutory negligence on an installation electrician for failures within the DNO system which is out of their control, and covered by a different set of actually statutory legislation which 7671 is not.

Paul

p.s. it's been a long time since I was an apprentice, but not so long since I have been in education as I believe in lifelong learning.

I made two quotes, and sorry if you thought you were fast track,

I inserted my statements in RED to show the insertions.

DNO are not obliged to provide to earthing, and if you decide to upgrade to TT then AFAIK DNO are at liberty to remove their earth and inform you of this.

DNO are not changing their supply T is what DNO supply, it is not stated to be N, C or S .

BS 7671 is NOT statutory, your requirement to leave a satisfactory installation is.

earthing is the responsibility of the installation electrician, NOT the DNO.

how many electricians actually take into account the earthing system during their design? or do they just assume DNO will provide.?

 

[tom1]

I made two quotes, and sorry if you thought you were fast track,I inserted my statements in RED to show the insertions.

DNO are not obliged to provide to earthing, and if you decide to upgrade to TT then AFAIK DNO are at liberty to remove their earth and inform you of this.

DNO are not changing their supply T is what DNO supply, it is not stated to be N, C or S .

BS 7671 is NOT statutory, your requirement to leave a satisfactory installation is.

earthing is the responsibility of the installation electrician, NOT the DNO.

how many electricians actually take into account the earthing system during their design? or do they just assume DNO will provide.?

i would have thought that would be one of the first people looked at

 

[PBC_1966]

if you decide to upgrade to TT then AFAIK DNO are at liberty to remove their earth and inform you of this.

But if you are still connected to the DNO's earthing facility, you haven't changed to TT. It is still TN because there is a solid metallic path back to the transformer.

You would need to install (or retain) your own earth electrode and disconnect your earthing lead from the supplier's TN-S earth or TN-C-S neutral to change to TT.

 

[steptoe]

Why is an earth electrode at the service entrance a problem with either system? Yes, I'm well aware of the differences between all three systems. But why do you think an earth electrode as the customer's premises is somehow unsafe with either TN-S or TN-C-S/PME?

you obviously dont understand the difference between TNCS and PME

With either system there is likely to be an additional earth path by way of bonded pipework, structural metalwork, etc.

They don't allow a water-pipe electrode as the earthing means for TT, and have not done so for years. But that's not what we're talking about.

You're arguing that it's somehow unsafe to add an extra earth electrode with a TN system. I'm pointing out that it's a requirement to bond metallic pipework (as you have stated yourself in another thread that you would always do), and that therefore if that metallic pipework is already effectively an earth electrode it's electrically no different.

electrically it is massively different, if you are so keen on regs, read up on it as to why its different

Why do you consider TT to be superior? Are you aware that in many places TT is actually prohibited?

this I await, in normal domestic? I have never worked anywhere TT wasnt seen as superior, or yet to find any reason why it wouldnt be.

True. But in the case under examination they have already provided one. They can't just come along and disconnect it without regard for the safety of the installation.

the electrician has provided a TT system, so yes DNO could remove their bonus earth.

If you had a TN-S system without any extra earth electrode at the premises (intentional or incidental by way of bonded pipes etc.), do you think the DNO could just cut the earthing conductor without bothering to tell you?

I already answered that in previous post

BTW, in case you are wondering,

I dont have TT at my house, its currently TNS, though it will be TT when I can be bothered to change it over and inform DNO to remove their earth.

 

[steptoe]

But if you are still connected to the DNO's earthing facility, you haven't changed to TT. It is still TN because there is a solid metallic path back to the transformer. You would need to install (or retain) your own earth electrode and disconnect your earthing lead from the supplier's TN-S earth or TN-C-S neutral to change to TT.

you are only connected at the DNO agreement, it belongs to them, in the same way they can disconnect your supply any time they want, they can also disconnect your earth, as long as they inform you.

the only cable they can not disconnect is your neutral.

 

[PBC_1966]

you obviously dont understand the difference between TNCS and PME

Yes, I'm aware of the difference, but whether we're talking about a supply system which starts out as PME, PNB, or plain old TN-S, what harm will providing an extra earth electrode do?

electrically it is massively different, if you are so keen on regs, read up on it as to why its different

How is it different? You're arguing that with a TN-S system it's somehow unsafe to drive a few feet of rod into the ground and connect it to the installation's earthing system.

So why do you not think it equally unsafe to connect the earthing system to a length of copper pipe which is buried in the ground?

this I await, in normal domestic? I have never worked anywhere TT wasnt seen as superior, or yet to find any reason why it wouldnt be.

Yes, in domestic and everything else. The U.S. does not use TT at all, and it is specifically prohibited by the NEC.

Why should TT be seen as superior?

the electrician has provided a TT system, so yes DNO could remove their bonus earth.

Nobody has provided a TT system. He's just added a supplemental earth electrode to an existing TN system.

BTW, in case you are wondering, I dont have TT at my house, its currently TNS, though it will be TT when I can be bothered to change it over

Good luck with the downgrade!

 

[steptoe]

Yes, I'm aware of the difference, but whether we're talking about a supply system which starts out as PME, PNB, or plain old TN-S, what harm will providing an extra earth electrode do? I REALLY DIDNT WANT TO SAY THIS BUT YOU ARE NOW GETTING ME UP THE WALL WITH YOUR COMMENTS,

IT STARTS OF AS TT,

IF YOU DONT UNDERSTAND SUCH SIMPLE PRINCIPLES THEN START POSTING IN THE LEARNING ZONE

How is it different? You're arguing that with a TN-S system it's somehow unsafe to drive a few feet of rod into the ground and connect it to the installation's earthing system.

So why do you not think it equally unsafe to connect the earthing system to a length of copper pipe which is buried in the ground?

Yes, in domestic and everything else. The U.S. does not use TT at all, and it is specifically prohibited by the NEC.

Why should TT be seen as superior?

Nobody has provided a TT system. He's just added a supplemental earth electrode to an existing TN system.

Good luck with the downgrade!

Admin, can we have a blocking facility please.?

is this really what we provide these days?

and people are complaining about Polish people taking work from us, is it any wonder.?!

 

[PBC_1966]

As you've not made any attempt to answer the question and have now resorted to insults in private messages, I'll guess I'll just have to assume that you have no explanation as to why you think the extra earth electrode is dangerous.

 

[m4tty]

I thought the forum was a place for people to discuss things. I read most threads trying to learn. Clearly some people 'know it all' so why do you need to come on here. I would like to see steptoes answers to the questions asked in this thread as he clearly is knowledgable but no need to insult people and starting blocking eachother. Thought id logged onto screwfix for a second then lol. bad day explode

 

[a1]

Bloody Heck,

Here we go again.

Steps, I know you feel strongly about this, but there really is no need to throw insults about.

As for the PM allegation, if that is true, then I am shocked!

The PM facility is not there for that!!!

If the answers can't be kept civil, don't bother relplying. (to everyone!)

Before I was interested in Sparking - the first job that I did was to run armoured down to my workshop/shed. I wired everything in and had a qualified spark in to connect the SWA in at both ends and test.

I received advice from plenty of sparks before doing it.

My supply is a TNS System and I have no Earth Electrode at at workshop end (distance of 20-25 Meters).

I was advised that I could bang one in if I wanted to. But I didn't.

If it were a TT or PME System, then I would have.

So PLEASE, let's keep the insults to ourselves, or vent our anger out on a different forum - should you need to, Guys.

I can't see why someone would want to bang in an earth Rod on a TNS System, and I can't understand why someone would be dead against it if they did? I thought I knew about earthing systems? But clearly I don't!

:_|

Nothing wrong with a healthy argument. But insults and such like will end up in having posts/threads removed and an infraction(s) issued. X(

(PS. I haven't read all of this thread (Yes I know, I will go to page one and read it now) - and I haven't read the complete world famous thread on "Exported Earths" either).

Best Wishes,

Admin.

 

[ianmacd]

Reading between the 'banter' (I do hope thats what you all meant it to be), what it looks like this boils down to is that adding a rod could lead the DNO to believe that the instalation has been converted to TT and that it is safe for them to remove their supplied Earth. If the instalation has been designed for a TN system then the required disconnect times may no longer be achievable and thus potentially a danger.

As for the issue of culpability for any accidents, then I would imagine the DNO could get away with that as they will have, possibly correctly, seen that the instalation has an alternative Earthing supply at which point the blame could well fall upon the last person to work on the system for either supplying or not removing the secondary Earthing provision.

I think we will all agree that it is not a good thing to be without an Earth connection so converting to TT does have the advantage that the DNO can never remove it (either accidentially or deliberatly).

 

[spinlondon]

Always assuming that the DNO did not provide the rod in the first place.

 

[ianmacd]

Always assuming that the DNO did not provide the rod in the first place.

Why would the DNO put a rod on a private property? If they did it would surly be owned by the property owner anyway.

 

[spinlondon]

I don't know.

BS7671 states in TN systems, that where the earthing is provided from a public or other supply system, compliance with the necessary conditions external to the installation is the responsibility of the distributor.

BS7671 also allows that PE and PEN conductors may additionally be connected to Earth, such as at the point of entry into the building.

 

[ianmacd]

Isn't that then the cable is rodded (if that's a word) and not a seperate cable back to the MET? I would also suspect it may not need to be accessable.

 

[Andy™]

as per ESQCR, where possible, DNO is required to make the neutral available as an earth (PME), or a seperate earth (TNS) ( 24 (4) ). also, if an earth is provided, it must be maintained (24 (1) (B) ).

cant see anything in there that states the DNO are to remove their earth if the installation has a rod installed.

 

[ianmacd]

[quote name='Andy