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Topic Title: DNO changed supply from TT to PME
Topic Summary: Who is responsible for remedial works
Created On: 10 July 2014 10:09 AM
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 10 July 2014 10:09 AM
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ieechrise

Posts: 10
Joined: 19 January 2005

I was called to a customer who requires an external socket in his garden, not a big issue in itself. At the time of my visit the supply was TT, the incomer from the pole was inside his neighbours loft space and the very old wiring insulation had disintegrated. I suggested he contact the DNO about it as it looked like the drop wires had overheated (maybe just long term weathering).

Subsequently the DNO changed the supply to both properties, drop wires re routed and new poles installed. When I went back to the site I found they had wired the supply as pme.

The customer has no idea what that means, but he has a garage away from the house with a supply via an underground cable somewhere. I explained as far as he could follow, that exporting the earth is no longer good practice and the garage/workshop now needs a TT electrode and similarly the proposed garden socket.

Should the DNO foot part of the bill?, should they have made the change bearing in mind the existing garage supply?

Thanks in advance for any responses.

rgds
 10 July 2014 10:35 AM
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Parsley

Posts: 960
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Are there any extraneous conductive parts that need bonding in the garage?

If there aren't is it an issue?

Regards
 10 July 2014 11:10 AM
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AJJewsbury

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What have the DNO done exactly? Have they just offered a PME terminal, which you can ignore an keep everything TT as it was, or have they taken the old electrode away and re-connected the installation to their CNE?
- Andy.
 10 July 2014 11:27 AM
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ieechrise

Posts: 10
Joined: 19 January 2005

Parsley- There is a substantial metal frame around the doors

Andy- Their contractor connected the whole system as PME and placed a sticker indicating exactly that. The electrode has been disconnected.

thanks for the responses
 10 July 2014 11:43 AM
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AJJewsbury

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Their contractor connected the whole system as PME and placed a sticker indicating exactly that. The electrode has been disconnected.

But original electrode & RCDs still present & serviceable? If so you presumably could convert back to TT for a negligible cost and then start from where you were before - if you wanted.
- Andy.
 10 July 2014 11:49 AM
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slittle

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So assuming it's got an RCD at the mains position which it must of had as a TT installation, drop the "PME" earth, put the electrode back in, problem solved.


Or is it the fact there never was an RCD that's now caused the "contractor" to connect the PME earth to at least provide some sort of chance for the installation to disconnect ??


Stu
 10 July 2014 12:21 PM
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ieechrise

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Stu- it had a new board about three years ago, split rcd's
 10 July 2014 12:26 PM
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OMS

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Joined: 23 March 2004

What's the bonding like ?

Personally, if that's OK then I suspect you may be getting a little carried away with perceived risks from PME

Regards

OMS

-------------------------
Failure is always an option
 10 July 2014 12:57 PM
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AJJewsbury

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There is a substantial metal frame around the doors

I'd be very dubious about bonding garage door frames - firstly I'd doubt whether they're really extraneous (i.e. can introduce a potential) and even if they are I'd want to weigh the increase shock risk to those stood outside the building against any benefit to those inside. (Which side of a garage door are you usually when you touch it?)

- Andy.
 11 July 2014 10:30 AM
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ieechrise

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Joined: 19 January 2005

OK. to conclude the thread, verify the bonding and then the options are

1) revert to TT

2) ignore the change

based on either option would consensus be that the new socket outlet in the garden can be completed in 3 core swa (armouring earthed for mechanical rather than functional), no earth spike.

Thanks for the responses

Edited: 11 July 2014 at 01:10 PM by ieechrise
 11 July 2014 11:45 AM
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daveparry1

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I there are no extraneous metal parts close by (eg copper water pipe etc) I would ignore the change.
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