Discuss Exporting the earth? in the Industrial Electrician Talk area at ElectriciansForums.net

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R

Robo

Im not 100% on earthing for submains. If the supply is tnc-s you are not ment to export the earthfrom db to say a detached garage?If i did export the earth could it not be classed as TNS instead?? Or to keep it TNCS run a seperate earth form cutout.Or just have the garage as a TT.

Are you aloud to export TNS from 1 db to another?

Or i could rod the garage and then it would be seperate?
 
Under the Electricity safety, quality and continuity regulations 2002 you cannot use a suppliers earth to an out building, on a TNC-S Earthing arrangement, so the detached garage effectively becomes a TT installation with an earth electrode installed in the ground.

If you use SWA to supply the garage the armour must not be terminated at the garage end of the cable.
 
Bit unsure re your TNCS to TNS

If you create a new earth at the garage that would have to be via a rod so it would be TT.

If you were to continue with a earth from the TNCS system it would remain that system and not change to TNS. Some DNO companys don't like you exporting it.


How far away is the detached garage and don't forget to bond in the garage.
 
Bit unsure re your TNCS to TNS

If you create a new earth at the garage that would have to be via a rod so it would be TT.

If you were to continue with a earth from the TNCS system it would remain that system and not change to TNS. Some DNO companys don't like you exporting it.


How far away is the detached garage and don't forget to bond in the garage.

I dont actually have a job, im just enquiring for the future. Would it be ok to gland garage end and just not connect into earth bar, providing its insulated. If it was metal then use a stuffing gland and dont bother with armours.
 
Under the Electricity safety, quality and continuity regulations 2002 you cannot use a suppliers earth to an out building, on a TNC-S Earthing arrangement, so the detached garage effectively becomes a TT installation with an earth electrode installed in the ground.

If you use SWA to supply the garage the armour must not be terminated at the garage end of the cable.

That is absolutely incorrect, please read the Guide that I posted and Guidance Note 8.



This is the link to the thread: http://www.electriciansforums.net/e...159-good-guide-exported-pme-outbuildings.html
 
If you are useing the earth from the TNC-S to protect the swa cable and then isolating it from the garage which now becomes TT.

I would use a insulated box so that both earths are kept seperate so you are only transporting the line conductors.
 
Seems the myths and mis-information on this topic continues... To my mind, Rods (TT) should always be considered as your last choice, not a first choice!!!
 
Under the Electricity safety, quality and continuity regulations 2002 you cannot use a suppliers earth to an out building, on a TNC-S Earthing arrangement, so the detached garage effectively becomes a TT installation with an earth electrode installed in the ground.

If you use SWA to supply the garage the armour must not be terminated at the garage end of the cable.

God 'elp us.....what it it with outbuildings that promps otherwise competant electricians to spout complete nonsense?:confused:
 
The ESQCR replaced the old Electricty Supply Regulations 1988 in 2002. Us older members of the forum will remember that in the old Electricity Regulations there was a section concerning PME systems and it was if I remember correctly advised not to export an earth without the DNO permission. If I remember right it even advised that if you had an outside tap fed from the house it should be sheathed to protect against shock.

It as to be remembered that when these regulations were in force protection devices and installations were not as safe as they are now. The only installation in a domestic situation which had RCD protection, or then ELCB protection was a TT and so exporting earths were not as safe as they are now.

With todays modern protection, bonding and the majority of outside appliances being double insulated the exporting of an earth in a TNC-S system is not so dangerous. IMO I can see nothing wrong with it.

But old sparks are a die hard breed, I will still call the DNO and ask if they will let me export. Today I agree that the likely hood of an answer being "What are you asking for" is the one you will get. If the garage/outbuilding is perhaps a good distance from the house I would still most likely TT the building as that is what IMO is the way it should be.

I can't argue the fact that today even if the building is 40 metres from the house, it's not got services to it in metal, or is of a metal construction then why not export the earth, but as I'm one of those die hard old breed that is my opinion.

I'm would also like to add that I can't understand why there is such a downer in a TT installation. I'm not sure with todays protection devices why a system that as been in use for much longer than the other type of earth system is considered a last resort.
 
God 'elp us.....what it it with outbuildings that promps otherwise competant electricians to spout complete nonsense?:confused:
from j.mawers post.....

Where the installation in the garage is supplied by an armoured cable, the armour or any protective conductor in the cable must not be
connected to and must not be simultaneously-accessible with any exposed-conductive-parts in the outbuilding.
 
Not quite sure why the last post got a reference to me as the quote is from "Wiring matters" but it is also from the section regarding using TT system if the garage contains extraneous conductive part i.e. if you make the garage TT then don't connect it to the exported earth from the main building.
 
Last edited:
@ j.mawer it was a ref to post number 4 (your link)

Just to confim the DNO do not allow exporting of PME

You must isolate the pme in an enclosure then TT the buildings instalation .
 
from j.mawers post.....

Where the installation in the garage is supplied by an armoured cable, the armour or any protective conductor in the cable must not be
connected to and must not be simultaneously-accessible with any exposed-conductive-parts in the outbuilding.

So you didn't read the paragraph below that regarding 'main protective bonding where PME conditions apply'?

The point is you have a CHOICE-often the only reason for selecting a TT system at the destination is economic reasons because of the way main protective bonding is sized for TN-C-S supplies.

You stated that ESQCR specifically forbids the methods that IET Guidance Notes 8 and 1 prescribe regarding using the suppliers earth to outbuildings on a TN-C-S supply.

Where is this in ESQCR because I am very familiar with it's content and the content of BS 7430 earthing & bonding and have no such reference in my copies of these documents!
 
regulation 543.4.1 states that in Great Britain regulation 4 of the Electricity, Safety, Quality and Continuity Regulations 2002 prohibit the use of PEN conductors in the comsumers installation.
 
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