A good guide For 'exported PME' and outbuildings!

[IQ Electrical]

For anyone bored by the constant myths and rumours regarding this subject, have a read of this guide from the IEE on supplies to detached outbuildings.

It was published in 2005 but the important bits remain unchanged and might be of some help!

 

[JD6400]

agricultural and horticultural premises are define in BS7671 as,, rooms, locations or areas where - livestock are kept, -feed, fertilizers, vegetable and animal products are produced, stored or processed, - plants are grown, such as greenhouses. pretty much anywhere on a farm apart from the actual farmhouse

Hi oldAl , where do you find this ?
Have to admit , i treat the whole property as if it will house livestock anyway as you never know what that particular farms policy will be next year let alone in 15 years .

 

[andyb]

right, here you go again, continually stating PME, do you know the difference between PME and TNCS ?

Then please enlighten us not as clever as you & explain the diference.

How on earth do you get from this

the following is an excerpt from ESQCR Special consideration should be given to the earthing and protection arrangements for certain installations where reliance on the connection of the consumer’s protective conductor with the distributor’s combined neutral and protective conductor could result in more significant risks. For example, installations where it may prove difficult to attach and maintain all the necessary equipotential bonding connections (e.g. farms or building sites), installations at certain wet environments (e.g. swimming pools and petrol filling stations) and certain installations outside the equipotential zone of buildings

To this

do you know you are supposed to ask the DNO for permission to take a TNCS or PME earth outside the building to the one they have supplied it to? and do you know what their standard answer is? it is "NO" , wonder why that is? btw, their is an enormous amount of documented proof about the dangers of 'exporting' TNCS earthing, makes you wonder why agricultural premises are prohibited from utilising TNCS or PME supplies. maybe you should have a look at the 'Farady cage' scenario again to understand the difference in potentials, the DNO supply an artificial earth, this can be at a different voltage potential than the general mass of earth that we stand on, this is why we use equipotential bonding, to bring everything to the same potential, I do hope you understand these basic principles of electrical systems.

If you read my post 112 you will see that is what I said.

 

[Guest123]

Hi oldAl , where do you find this ?
Have to admit , i treat the whole property like this anyway as you never know what that particular farms policy will be next year let alone in 15 years .

Part 2, definitions.

 

[Engineer54]

right, here you go again, continually stating PME, do you know the difference between PME and TNCS ? as for no-one being prosecuted for exporting it, how many people do you know have been prosecuted for not notifying part P work? the following is an excerpt from ESQCR Special consideration should be given to the earthing and protection arrangements for certain installations where reliance on the connection of the consumer’s protective conductor with the distributor’s combined neutral and protective conductor could result in more significant risks. For example, installations where it may prove difficult to attach and maintain all the necessary equipotential bonding connections (e.g. farms or building sites), installations at certain wet environments (e.g. swimming pools and petrol filling stations) and certain installations outside the equipotential zone of buildings

None, which is part of my point!! lol!!

Special Considerations is fine, ...don't see anywhere in that passage that say's ''not permitted'' or other terminology relating to the same thing!! Where there is no difficulty attaching and maintaining equipotential bonding cables such as farms, outbuildings there isn't going to be a problem is there. If your extending the original equipotential zone, then as long as that bonding cable from the MET is of the correct sizing what's your problem??

I do agree with the Filling Stations, Caravan and Caravan Sites, and Public Swimming Pools, Mariners etc...

 

[JD6400]

Part 2, definitions.

Thanks for the reply Lenny , now feel a bit of a Pratt having asked such a obvious question !:grinningelf:

 

[Engineer54]

agricultural and horticultural premises are define in BS7671 as,, rooms, locations or areas where - livestock are kept, -feed, fertilizers, vegetable and animal products are produced, stored or processed, - plants are grown, such as greenhouses. pretty much anywhere on a farm apart from the actual farmhouse

Give us the reg/section number that states that PME Isn't permitted or is recommend against for all those locations where livestock isn't involved?? I'm not totally disagreeing with you here by the way, i can see where there could be good reasoning behind installing a good TT system, ... just that your not giving me any of them, your just trying to convince others here that death is just around the corner when PME or if you like TNC-S is mentioned!! And that is just pure scaremongery in my book!!

 

[andyb]

705.411.4 TN system

 

[Guest123]

705.411.4 TN system

That refers to a TN-C system, having combined neutral & protective conductors throughout the entire system i.e supply & installation side.

TN-C-S as we know, has seperate (S) neutral & protective conductors on the installation side.

 

[andyb]

That refers to a TN-C system, having combined neutral & protective conductors throughout the entire system i.e supply & installation side.

TN-C-S as we know, has separate (S) neutral & protective conductors on the installation side.

Having read it I now agree with you, in that case where does i say that pme is not allowed? I've always taken that reg to cover t-n-c-s but as you point out it only says t-n-c

 

[Guest123]

Having read it I now agree with you, in that case where does i say that pme is not allowed? I've always taken that reg to cover t-n-c-s but as you point out it only says t-n-c

The only reference to PME not being 'recommended' is as my post #114 where a metal grid would have to be laid in the floor of the area in question IF it was to have livestock present.

 

[Engineer54]

Think you'll find he's using ''Considerations'' as meaning ''Not Permitted'' which is not the case at all. He just doesn't like anything that comes close to a TNC-S, and will throw every bit of text he can find at it!! lol!! Another case of the perpetuation of the Myths and Scaremongery that surrounds PME earthing systems!!

I wonder how many times these people have installed outside socket outlets fed from PME systems, for use with garden tools/appliances, ....And i wonder how many of those socket outlets they have roded ?? lol!!!

 

[oldAL]

engineer54, if you could be bothered to actually research what you are pushing as being good workmanship then you would also find that it would take extrenuating circumstances for it to be acceptable for TNCS to be exported, yet again you keep saying PME when the issue is TNCS, even this thread is titled PME when in actual fact the great majority of it refers to TNCS, do you have the simple grasp of the fact they are in fact two different things? you are the one perpetrating the myth that PME and TNCS are the same thing, most competent sparks would know the difference and not keep referring to TNCS as being PME, I have already clearly stated on here that I find PME systems very good and acceptable, it is TNCS systems that I find flawed, and even worse than that, so called professionals that dont know the difference and keep referring to TNCS as being PME.

 

[Engineer54]

Oh I know the difference, but i'm not going to let you run away, trying to convince others that every time they see a PME head, it's not PME, but TNC-S so best not extend it to a garage or outbuilding. Your basically a scaremonger that perpetuates but can't substantiate!!

So what are you saying now then, ...That there is no PME supplies in the UK there all TNC-S ?? ...Total absolute Piffle, there's only one person here coming out with myths and it certainly isn't me!!

You're waffling on now, but still haven't come back with anything to substantiate any of your wild claims, even on TNC-S systems let alone PME systems....
So give us a senerio of the terrible risks associated with your impression of a DNO supplied TNC-S earthing system??

 

[malcolmsanford]

Turn your back for 2 weeks and miss all the fun ...........................:grinningelf:

 

[gooner1984]

Turn your back for 2 weeks and miss all the fun ...........................:grinningelf:

your lucky turn my back and i get stabbed in it