Exporting the earth?

Discuss Exporting the earth? in the Electricians' Talk area at ElectriciansForums.net

SimpleSimon said:
I'll just leave it on Im young enough to still take meaning on the saying "Respect your elders" ;)
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right attitude. but then again, us older ones have to respect the younger generation for it is they that will select our nursing homes.
 
TNC-S is considered a lot less dangerous now with concentric supply cables, where the PEN conductor surrounds the line conductors like the armour but as a copper core, thus making it impossible to cut through the PEN conductor (i.e. digger bucket) without creating a short circuit and ensuring disconnection of the DNO´s protective device back in the substation. Not sure how many underground TNC-S supply cables are concentric though!!! Anybody know??
 
The general opinion of the various DNO's is that a loss of the PEN does not happen and they have sophisticated monitoring devices in place. There was a report by the IEC some time ago that basically concluded that 'the incidence of a break of the neutral conductor in low voltage systems is so low as to not deserve any consideration'.
 
SimpleSimon said:
True. It's also us who'll push your wheelchairs down the hill when you get a bit narky!
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i'm over the hill already, but shove my wheelchair down further and find out what walking sticks are really for. LOL.
 
Dave_ said:
TNC-S is considered a lot less dangerous now with concentric supply cables, where the PEN conductor surrounds the line conductors like the armour but as a copper core, thus making it impossible to cut through the PEN conductor (i.e. digger bucket) without creating a short circuit and ensuring disconnection of the DNO´s protective device back in the substation. Not sure how many underground TNC-S supply cables are concentric though!!! Anybody know??
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New supplies, i have some concentric here i got off a jointer when i was meter fitting, also got a few lucy cutouts, the concentric for those that don't know is copper outer core (neutral and earth) with a solid aluminium core in the middle (line conductor).
 
telectrix said:
the following post is meant to be read in the spirit it is posted.

having been in the trade for a while, when the height of accuracy of resistance measurement was an AVO 7, with a bit of good eyesight you could just about get an accuracy of 1 and a bit ohms, not the zillionth of an ohm we read to now, a caclculator was a slip stickmade by thornton's who now make chocolate, and the only digital equipment was a red led watch, on some boffins drawing board, sketched in pencil, it was usual to TT outbuildings, as most installs were TT anyway . nowadays we have a choice. i only export the earth if the outbuilding has no extraneous metal conductive parts. the dangers inherent having been expained on this thread better than i can. so far nobody has been electrocuted on one of my installs, so i will continue as an old fossil until my legs give way, or goverment increase pensions to a level wherein i can live in the style to which i am accustomed.
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I too am from your era, and i still have my old AVO 8. ...lol!!!

The difference between a TT system then and now, is that most of the younger sparks of today will rely on an RCD device for ground fault protection with a TT system. Whereas in our day the sparks had only the rod(s) to give them that protection. So now days, they just whack a rod in the ground and if it's under 200ohms it's a good-un!!! I bet that if you look around at some of these newly installed rods, most will be right by the side of the building wall too. The very last place to drive a rod!! ...Why, because that's where all the building rubble is going to be. I also bet that a good number of those rods have been cut short because they ''Have'' hit in-passable rubble, so the chances of gaining a decent Ra is even further diminished!!!

Most of the newer installations generally also rely on a single rod, whereas in my day, if a high reading was present on the initial rod a second rod was driven. It wasn't that uncommon in the past, to see 3 driven rods, especially in unfavourable ground conditions/locations... The other thing is, ...how many modern day sparks know how to maintain a TT system?? How many know of chemical conditioning, what chemicals to use, and some of there drawbacks, ....or know about conductive mortars and when and how to use them?? Very few would be my guess!!! Now days, almost total reliance is given over to an RCD, ....which although very good, are prone to failure. Then that rod with an Ra of 200ohms isn't going to operate any protective device in a
time that will give any meaningful protection....

Installing a ''Good'' TT system requires both skill and experience, and money too, if it's to be installed properly. It's not just a case of whacking a rod in the ground and hoping for the best ...lol!!!
 
IQ Electrical said:
The general opinion of the various DNO's is that a loss of the PEN does not happen and they have sophisticated monitoring devices in place. There was a report by the IEC some time ago that basically concluded that 'the incidence of a break of the neutral conductor in low voltage systems is so low as to not deserve any consideration'.
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I couldn't agree more with you IQ, I have a friend that has spent the whole of his working life with the leccy board and DNO company. He is now a regional manager. He has only known of 2 such cases, both of which were tripped out on there protection relays before any detrimental affects had time to establish within the fault area. Yet you always get those that will tel you they know of many such incidents..... Basically it's all down to hearsay, and scaremongery. If the system was anywhere near as dangerous as some would have you believe, it would NOT be a part of ours and many others countries supply distribution system.
 
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antimatter said:
Why do you disagree?
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Antimatter I disagree because you are incorrect.
If you check bs 7671 you will find no restriction or even mention of TNCS supplies and outbuildings other than in special locations,it is bs 7671 that we work to.
The DNO are only interested in the installation comlying with bs 7671.
Some may prefer to separate and TT, that is their choice.
But PLEASE get your facts right before posting that exporting TNCS is not permitted...IT IS.

Thanks to IQElectrical for sticking with this one....you displayed a lot more patience than I would of if I'd been around.
 
wirepuller said:
Antimatter I disagree because you are incorrect.
If you check bs 7671 you will find no restriction or even mention of TNCS supplies and outbuildings other than in special locations,it is bs 7671 that we work to.
The DNO are only interested in the installation comlying with bs 7671.
Some may prefer to separate and TT, that is their choice.
But PLEASE get your facts right before posting that exporting TNCS is not permitted...IT IS.

Thanks to IQElectrical for sticking with this one....you displayed a lot more patience than I would of if I'd been around.
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Not if there is any extraneous metalwork in the outbuilding.
 
as long as the extraneous metal is bonded back to the MET. suitable bonding installed.
 
antimatter said:
Not if there is any extraneous metalwork in the outbuilding.
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What's the difference, whether there is extraneous metalwork at/in the outbuilding or not?? If there is, you bond any extraneous metalwork back to MET, same as you would at any other type of building, all you are basically doing is ''extending the installations equal-potential area. You've been listening to too many scaremongers, that have a dislike of PME supply systems.
 
Because if there is an earth fault on the outbuilding, and both the outbuilding and main building are linked together by means of earhing, the fault on the outbuilding is then present in both buildings, that's why we separate and TT the outbuilding so the fault is sent through the earth electrode and to the general mass of earth.
 
antimatter said:
Because if there is an earth fault on the outbuilding, and both the outbuilding and main building are linked together by means of earhing, the fault on the outbuilding is then present in both buildings, that's why we separate and TT the outbuilding so the fault is sent through the earth electrode and to the general mass of earth.
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Not necessarily. TT may be the preferred method for this reason but you have option of the two, to stick with TNC-S or seperate and TT the outbuilding.
 
I don't think you read my last post..... ''bond any extraneous metalwork back to MET, same as you would at any other type of building, all you are basically doing is ''extending the installations equal-potential area.''

There would be exactly the same fault conditions no matter what type of supply is installed, and there are certainly no restrictions on extending a TN-S system!!!!
 
Dave_ said:
Not necessarily. TT may be the preferred method for this reason but you have option of the two, to stick with TNC-S or seperate and TT the outbuilding.
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There is no option because of the earth potential introduced if there is extraneous parts in the outbuilding, therefore not complying with the regs.
 
Engineer54 said:
I don't think you read my last post..... ''bond any extraneous metalwork back to MET, same as you would at any other type of building, all you are basically doing is ''extending the installations equal-potential area.''

There would be exactly the same fault conditions no matter what type of supply is installed, and there are certainly no restrictions on extending a TN-S system!!!!
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Thats because the earth system is what it says in the name S - separate earth. As oppsosed to a combined Neutral and Earth conductor.
 
Dave_ said:
Thats TNC!!!

TNC-S Terra Neutral Combined (DNO!!!) Seperate (Consumer!!!)
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Yes we all know what TNC-S stands for Dave well done for that, i was pointing out to engineer 54 that there are differnt rules on TNC-S and TN-S thats all, there is no need for you to explain very simple acronyms to us all thank you.
 
Antimatter,

With the greatest of respect, you are 100% incorrect in this instance. Please examine the afforementioned literature and also contact your local DNO for further assurance if needs be.

There are probably hundreds of seperate threads on these forums regarding the exporting of a suppliers TN-C-S system and all conclude with the same answer which is, it's absolutely fine to do so providing any exposed steelwork/pipework that may be present in that building is connected to the installation M.E.T/B.E.M.T via a suitably sized main protective bonding conductor.

To continue in your current vane is non productive and misleading to others.

Regards.
 
Lenny said:
Antimatter,

With the greatest of respect, you are 100% incorrect in this instance. Please examine the afforementioned literature and also contact your local DNO for further assurance if needs be.

There are probably hundreds of seperate threads on these forums regarding the exporting of a suppliers TN-C-S system and all conclude with the same answer which is, it's absolutely fine to do so providing any exposed steelwork/pipework that may be present in that building is connected to the installation M.E.T/B.E.M.T via a suitably sized main protective bonding conductor.

To continue in your current vane is non productive and misleading to others.

Regards.
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You are wrong, TT and rod it, end of story, sorry, mod or not you are not correct
 
From the IET's many threads on this subject

"Generally speaking the exportation of a TN-C-S supply is the decision of the local DNO and only done with their permission. In the absence of such permission it would be recommended to use a TT system and RCD protection.
 
This is a forum and it is my right and everyone elses who reads this to air their options, yes even you! no one is being mislead, we are INTERPRETING the regs, thats all. Nothing else.
 
antimatter said:
You are wrong, TT and rod it, end of story, sorry, mod or not you are not correct
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With no respect as i have lost any possible after reading the rubbish and poor attitude you have shown here, i am in utter disbelief. It has been clearly pointed out to you by IQ and many others than you are wrong. I have made mistakes on this forum and been corrected and been glad of the correction as this forum helps all of us learn no matter how experienced. You clearly think you know best. When you DONT. I advise you eat humble pie admit a mistake post an appology and be done with it. Or how will anyone take your advise seriously again? And you can export a tncs earth!!
 
Hawk81 said:
With no respect as i have lost any possible after reading the rubbish and poor attitude you have shown here, i am in utter disbelief. It has been clearly pointed out to you by IQ and many others than you are wrong. I have made mistakes on this forum and been corrected and been glad of the correction as this forum helps all of us learn no matter how experienced. You clearly think you know best. When you DONT. I advise you eat humble pie admit a mistake post an appology and be done with it. Or how will anyone take your advise seriously again? And you can export a tncs earth!!
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Where does it say im wrong hawk81?
 
Far too much Miss-information and too many scaremongers in the UK with regards to PME installations. You would think that after all these years of the system being supplied by one form of supply authority or another that it would be far better understood. You just don't get this hostility towards PME/TNC-S in other European countries!!!

Perhaps these unbelievers should remember, that all those old TT systems (many going or gone bad) were converted to PME, and for a very good reason. It took years getting these installations a decent earthing system. Now it seems, these people want to return to the bad old days, and whack in Rods willy nilly, not really knowing or understanding what they are actually doing. Who is going to maintain all these TT systems, certainly not the electrician that installed them... Oh, i forgot there is always that RCD, ......So no problem ....NOT!!!!
 
Hawk81 said:
With no respect as i have lost any possible after reading the rubbish and poor attitude you have shown here, i am in utter disbelief. It has been clearly pointed out to you by IQ and many others than you are wrong. I have made mistakes on this forum and been corrected and been glad of the correction as this forum helps all of us learn no matter how experienced. You clearly think you know best. When you DONT. I advise you eat humble pie admit a mistake post an appology and be done with it. Or how will anyone take your advise seriously again? And you can export a tncs earth!!
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I would be interested to learn why my attitude is poor if you are calling what i write rubbish.
 
Antimatter,
can I ask then, if you are installing outside lights or sockets wired to the main building which is on a TNCS....do you rod them individually,and separate the earth....or use the TNCS?....I ask because logically if you are so appalled by the thought of a shed on a TNCS then presumably you feel the same about an outside light?.....if not why not?
 
Wow missed all this just go to show you what happens to a thread when you leave it. Not sure if you read my post #12. The Electricity supply Regulations did cover PME as a section, well the SEEB ones did, and this is where the exporting the earth debate originated.

Just read engineer54 part about TT without RCD protection, blimely he must be older than me becasue I remember using the fore runner of the RCD which was the ELCB back in the late 60's when I started out, and I think it was in use as early as the 60's and even the late 50's
 
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antimatter said:
From the IET's many threads on this subject

"Generally speaking the exportation of a TN-C-S supply is the decision of the local DNO and only done with their permission. In the absence of such permission it would be recommended to use a TT system and RCD protection.
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This statement doesn't say you can't use it, it says you have to contact your DNO. That doesn't make it a no no. The DNO go by BS7671 just like us and will most likely say yes. What reason wouldn't they.
But in the absence of the permission, you than have a CHOICE of a TT.
I can't see this statement supporting the prehibitation.
 
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