Earth Spike or Not?

[Andy Fenn]

Really need help on this one as like most subjects here, this is another one open to discussion.

Would you please tell me if I need to install an earth spike on a PME system when installing a new metal CU 22mtrs away from the house.

I know Ban you have already made comments on this but one person says one thing and so on.

A leckie friend of mine has been picked up during a recent check by the NICEIC, saying he MUST install one, so would appreciate all your top views.

How would you do it???????????

 

[Spark123]

From what I can gather, it is OK to use an exported PME earth providing there are no extraneous conductive parts in the external installation.
If however there are extraneous conductive parts which therefore require bonding to the MET, the PME earth should not be used and the system converted to TT.
I await the wiring matters ed 16 magazine on the iee website.

 

[andy]

personally, i would make it a TNS supply form the house to outbuilding. that way its similar to how a caravan site would work

 

[Spark123]

personally, i would make it a TNS supply form the house to outbuilding. that way its similar to how a caravan site would work

You would have to have a DNO install TN-S though.

 

[Andy Fenn]

Many thanks.

We are talking one light and 3/4 double sockets in a shed here and I was going to use the SWA to earth but as I said, a friend said this is a no no and I must use a spike.

Thanks for your time.

 

[Andy Fenn]

Spark, sorry but please expand on th eold DNO?

 

[Spark123]

DNO = Distribution Network Operator, see http://www.energylinx.co.uk/map.html

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I have just found the bit where I read it, see http://www.screwfix.com/talk/thread.jspa?threadID=23124&tstart=0
(thanks to ban who posted it this morning!)
It would appear that you can export a PME earth providing you use the correct size main eq bond conductors from the MET in the main property for extraneous conductive parts in the external installation i.e. 10mm² (I would verify conductor size with DNO first though).

 

[Adam_151]

From what I can gather, it is OK to use an exported PME earth providing there are no extraneous conductive parts in the external installation.
If however there are extraneous conductive parts which therefore require bonding to the MET, the PME earth should not be used and the system converted to TT.

The impression I get from the folks over at the iee forum, is that the presence of extraneous conductive parts does not preclude the use of an exported TNC-S earth, it mearly means that they have to be bonded back to the submain MET with the same size cable as is appropiate for doing the same in the main building, and that the same sized or bigger earthing cable is used to provide the earth to the submain board, and as this is not always practical, a way of avoiding having to install bigger cables is to convert the remote installation to TT

 

[Andy Fenn]

So please please tell me in simple English, for my outbuilding, 1 light, 4 sockets and no extraneous parts, can I use the SWA earth and wjust to wrap things up.....

would I be right in saying that if there are extraneous parts then I can either TT the installation or run some earthing in the correct size back to the MET