Out building earth

[Dave_]

Sorry. 542.1.1

This mentions you can connect to one of the types of earthing system.

 

[malcolmsanford]

I take it then Malcolm that you do not accept that you should first contact the DNO before exporting a TN-C-S earth, and that you would be quite suprised if they were to disconnect your supply, or just remove the PME connection after discovering that youhad exported such an earth without their permission?

If you read my OP in yesterdays thread you would see that as I'm old school and still remember the old ELecticity safety Regulations where there was a PME section included. I'm very much in favour with contacting the DNO about exporting earths but as I related the chances are the DNO will be be amazed you have contacted them regarding this in 2011.

But I have not mentioned exporting earths I was wondering why you are bringing DNO values into a domestic installation.

 

[Deleted member 26818]

I'm not particuarly bringing DNO values into a domestic installation.
Somebody brought up installing a rod along with exporting a TN-C-S earth.
Doing such would effectivly make that rod one of the multiple earths.
As such the DNO's often have particular requirements for such situations, and can get quite shirty about it.

 

[cagedanimal2010]

here we go again!!!

 

[Deleted member 26818]

Sorry. 542.1.1

This mentions you can connect to one of the types of earthing system.

This states that the main earthing terminal shall be connected with earth by one of the methods described etc.
Those methods being TN-S, TN-C-S and TT.
If you were then to read further, you would come across Regulation 542.1.5 "The earthing arrangements may be used jointly or separately for protective and functional purposes according to the requirements of the installation".
As I said there is nothing in either BS771 or ESQCR prohibiting this.

 

[malcolmsanford]

here we go again!!!

Not if I can help it off to bed before we are spiking all the way back to the power station.

 

[Deleted member 9648]

I have never,ever heard of the DNO getting uppity over a TNCS earth exported to an outbuilding,and I have never contacted them before doing so....In my experience all they are interested in is a cert saying it complies with bs 7671.

Simplified....
1.There are no regulations in Bs 7671 preventing a TNCS earth being used as the earthing system for an outbuilding..(except in some special locations as defined in bs 7671)
2.If there are extraneous conductive parts within the outbuilding that require main bonding then the requirements for bonding TNCS installations apply. This would mean a minimum 10mm bonding conductor would have to be installed from the outbuilding back to the MET. This may be impractical or it may not be cost effective.It may be cheaper to separate the TNCS earth and install a rod,in which case main bonding can run to the outbuilding DB.
3.If there are no extraneous conductive parts within the outbuilding requiring main bonding using the TNCS earth is in full compliance with bs 7671. As long as you carry out and cert the install to bs 7671 there is no need to contact the DNO.

That is how I've been doing it for 30yrs,and that is in full compliance with all relevant regulations.

If you are not in agreement....well, do it your own way

 

[Guest123]

I have never,ever heard of the DNO getting uppity over a TNCS earth exported to an outbuilding,and I have never contacted them before doing so....In my experience all they are interested in is a cert saying it complies with bs 7671.

Simplified....
1.There are no regulations in Bs 7671 preventing a TNCS earth being used as the earthing system for an outbuilding..(except in some special locations as defined in bs 7671)
2.If there are extraneous conductive parts within the outbuilding that require main bonding then the requirements for bonding TNCS installations apply. This would mean a minimum 10mm bonding conductor would have to be installed from the outbuilding back to the MET. This may be impractical or it may not be cost effective.It may be cheaper to separate the TNCS earth and install a rod,in which case main bonding can run to the outbuilding DB.
3.If there are no extraneous conductive parts within the outbuilding requiring main bonding using the TNCS earth is in full compliance with bs 7671. As long as you carry out and cert the install to bs 7671 there is no need to contact the DNO.

That is how I've been doing it for 30yrs,and that is in full compliance with all relevant regulations.

If you are not in agreement....well, do it your own way

Sounds bang on to me.

 

[Guest123]

This was the guidance we were given many years ago for installing street furniture.

Now there's a different set of regs altogether, if guys think using TN-C-S for a simple outbuilding is bad........street lighting in particular is a minefield!

 

[johnboy6083]

just a qusetsion fellas, im currently working on a job where we are installing lighting and power to metal kiosks, above well heads for a water board. they are having us take a supply from a panel in the main plant building, (3c10mm2 swa). we have been told to bond the armour at both ends, and to terminate the earth in the kiosk CU as normal. we are also installing an earth rod to each kiosk, which is then connected to the CU, either directly, or via an earth bar.

What is your take on this?

A lad earlier posted about a reg saying this is permitted, but i haven't got a copy of the regs to refer to.

I think that it is fine, as it is no different practicaly speaking, to bonding services, which can act as earth electrodes, or bonding to lighning protection, which uses earth electrodes?

Im just seeking some confirmation please?

John

 

[Deleted member 26818]

I take it that one of the cores will be used as an earth conductor?
Have they given you any instructions rgarding the earth rod resistance, or just asked you to bang one in?

 

[johnboy6083]

Yep. One of cores as cpc, and just asked us to bang it in.

 

[Geordie Spark]

Just a quickie ....... If the house is T T and the garage at the bottom of the garden is of wooden construction with a concrete floor, steel up-&-over door, one flossie light & 2 twin 13A sockets, am I right in thinking that it should be fed from the house in 2 core SWA with the SWA connected to earth at the house end only, and a spike provided at the garage to earth the CU in the garage?

Many thanks.

(sorry to be a pain)

 

[Deleted member 26818]

Yep. One of cores as cpc, and just asked us to bang it in.

The old Eastern DNO were happy with this, whereas the LEB would want the resistance of the earth electrode to be below 20Ω.

 

[Deleted member 9648]

Just a quickie ....... If the house is T T and the garage at the bottom of the garden is of wooden construction with a concrete floor, steel up-&-over door, one flossie light & 2 twin 13A sockets, am I right in thinking that it should be fed from the house in 2 core SWA with the SWA connected to earth at the house end only, and a spike provided at the garage to earth the CU in the garage?

Many thanks.

(sorry to be a pain)

I can see no reason to do this,I would use the main earth,although both methods are permitted.
411.5.1

 

[telectrix]

hmmm . if the house is TT, is there any reason not to bring the earth from the house ( as a 3rd core) and bang in a rod at the outbuilding as well. thus possibly bringing down the Ze for both the house and otbuilding?

 

[Deleted member 26818]

Just a quickie ....... If the house is T T and the garage at the bottom of the garden is of wooden construction with a concrete floor, steel up-&-over door, one flossie light & 2 twin 13A sockets, am I right in thinking that it should be fed from the house in 2 core SWA with the SWA connected to earth at the house end only, and a spike provided at the garage to earth the CU in the garage?

Many thanks.

(sorry to be a pain)

Yes this would be the best option, as the local earth at the garage could have a potential difference to that of the local earth at the installation electrode.