This seems to be a subject open to interpretation and everyone has their own views was just wondering if taking a supply in swa to an outbuilding and using an earth rod does it make a difference how you earth the sheath earth rod end at outbuilding or pme end at house personally can't see a problem with either option
Pme or earth rod
- Thread starter Rangers1882
- Start date
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You have not thought about it then?
You must earth the armour at the supply end in order to afford protection for the cable by the fault current device in the house and if you do TT it then the armour must be isolated at the outbuilding.
Therefore if the cable or armour is suitably sized for earthing and bonding there really is no point installing TT arrangements.
Can you combine the armour and a core to make it large enough for bonding?
IE a 6mm SWA cables armour isnt big enough to act as a bonding conductor, nor is the 6mm conductor itself, but could the armour and a conductor be used together?
Also this table:
http://www.earthingnuts.co.uk/pdf/pvc_xlpe.pdf
Suggests PVC - PVC cable has more armour than XLPE-PVC cable? Is that correct?
IE a 6mm SWA cables armour isnt big enough to act as a bonding conductor, nor is the 6mm conductor itself, but could the armour and a conductor be used together?
Also this table:
http://www.earthingnuts.co.uk/pdf/pvc_xlpe.pdf
Suggests PVC - PVC cable has more armour than XLPE-PVC cable? Is that correct?
Yes - provided the required CSA for bonding is maintained all the way back to the MET of the installation.
Kind Regards, John
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True - IF one's only concern relates to extraneous-c-ps in the outhouse. Indeed, by the same argument, one would not consider TTing the outhouse if it had no extraneous-c-ps.
However, as I've been saying, some people have other concerns.
Kind Regards, John
Yes, my complete answer was worded in response to the OP who wrote:
"This seems to be a subject open to interpretation and everyone has their own views was just wondering if taking a supply in swa to an outbuilding and using an earth rod does it make a difference how you earth the sheath earth rod end at outbuilding or pme end at house personally can't see a problem with either option."
They do but are they valid in 'usual/normal' circumstances?
Explain armour isolated at outbuilding ???
Insulated and not connected to anything.
That depends upon what you mean by 'usual/normal' circumstances. The only really 'serious' risk associated with exported PME earths that seems to twist some knickers only arises with a 'lost supply neutral' - which I would call neither 'usual' nor 'normal'. However, as I have described, in that extremely rare situation, there are theoretically some things to twist the knickers of those who are so inclined, even in the absence of any extraneous-c-ps.
Kind Regards, John
No, I meant usual/normal sized property where an extension could easily reach to the same distance as the shed/garage.
Oh, I see. Well, certainly in my case, my extension reel will reach any of the outbuildings in my garden - and, as I wrote earlier today, I think that any export of a PME earth outside of the house's equipotential zone carries similar (tiny) theoretical risks - whether the 'export' is by means of an extension lead, buried SWA connected to an 'electrical installation' in an outhouse, a metal soil pipe, a copper-plumbed 'outside tap' or whatever.
Your 'extension lead criterion' could presumably be used as an argument for not bonding extraneous-c-ps in an outhouse which had an 'electrical installation'?
Kind Regards, John
Oh, I'm sorry.
I'm not being clear; I meant if you had a house extension built which could be as far from the supply as a shed or garage.
I'm not being clear; I meant if you had a house extension built which could be as far from the supply as a shed or garage.
Oh Dear - we're doing well at talking at cross-purposes this evening
Yes, looking back, I can see that interpretation of what you wrote!But it's surely not just about distances - as I said, it's all about taking a PME earth outside of the equipotential zone. If one built an extension which reached three-quarters of the way down one's garden, 'overtaking' sheds as it did, the entire inside of that extension would surely be included as part of the house's equipotential zone?
Kind Regards, John
Precisely.
Whilst that sounds like agreement, I'm not actually sure what you are agreeing with!
I have certainly never suggested that distance is a relevant issue in this discussion. I know that eric does make a distinction on the basis of distance, but, as I understand it, that is a more subtle argument based on the likely extent of voltage fields in the ground due to PME earths and extraneous-c-ps bonded to them.
As far as I (my Devil's Advocate) am concerned, the tap or socket (into which a Class I appliance could theoretically be plugged) on the outside of the kitchen wall present similar risks (in the presence of a 'lost PME neutral') as does the electrical installation in a shed 40 metres away from the house. Do you agree?
Kind Regards, John
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