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Topic Title: TTor PME
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Created On: 29 April 2013 06:29 PM
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 29 April 2013 06:29 PM
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OldSparky

Posts: 583
Joined: 28 June 2011

Hello Peeps

i will try to keep short, but my mate needs advice on a subject so i said i would put on the forum.

Farm with 3ph TNCS supply, it is the end of line so a transformer is located on the pole in the farm yard.

its a dairy farm by the way.

He has to run a supply to a remote building with in the farm and is unsure wether to TT the remote building or other?

your words of wisdom would be appreciated.

for what its worth i said to TT it...

cheers
Paul
 29 April 2013 06:52 PM
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OMS

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Joined: 23 March 2004

You don't really have much option as whilst ESQCR doesn't prohibit PME on farms, most DNO's don't like it - neither does BS 7671 section 705

TT maks most sense in this case as you effectively need the RCD's anyway for BS 7671 compliance

regards

OMS

-------------------------
Failure is always an option
 29 April 2013 09:51 PM
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slittle

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You can probably guess what I'm going to say.........

TT it, if there's four legged animals about regardless of what the book says about grids in floors etc.

As OMS has said, you've got to RCD it at a maximum of 300mA anyway so a well placed rod or two and it's cracked. Just make sure you keep your rods away from any that the DNO have sunk.

Stu
 29 April 2013 10:19 PM
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OldSparky

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Joined: 28 June 2011

Originally posted by: slittle

You can probably guess what I'm going to say.........



TT it, if there's four legged animals about regardless of what the book says about grids in floors etc.



As OMS has said, you've got to RCD it at a maximum of 300mA anyway so a well placed rod or two and it's cracked. Just make sure you keep your rods away from any that the DNO have sunk.



Stu


glad you have said this, the transformer is about 150 meters away from where he would install his rod. The pole has a rod of course.

do you consider this far enough?

The existing supply was installed by others, not sure how its ended up not being TT .

It is possible that the rod on the pole is so close to what would be the consumers rod maybe the DNO thought it best to be PME?

would they think that way?
 29 April 2013 10:31 PM
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slittle

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150 meters is plenty but be careful there's not another rod close to the end of the service cable.

To be fair, I've got a couple of non livestock farms where PME has been provided. Doesn't mean we have to use it though.



Stu
 29 April 2013 10:31 PM
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slittle

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150 meters is plenty but be careful there's not another rod close to the end of the service cable.

To be fair, I've got a couple of non livestock farms where PME has been provided. Doesn't mean we have to use it though.



Stu
 30 April 2013 09:12 AM
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AJJewsbury

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Joined: 13 August 2003

transformer is located on the pole in the farm yard.

Is the supply definitely PME? If the transformer only serves the farm it might be PNB or even an outside chance of conventional TN-S (SNE). (might explain why the original wasn't TT'd).

- Andy.
 30 April 2013 05:51 PM
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KFH

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Joined: 06 November 2010

I am with the others - TT. Does the building have a metal frame that he can use as the earth?
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