Jump to content

DONT STAY LURKING AS A GUEST,

JOIN TEF AND BENEFIT FROM MEMBERSHIP:

CLICK HERE TO JOIN.
  •  
     
     
Countdown To Christmas!
 

 
  • 0

exporting earth again!!!


scrag

Question

Gotta quote an outbuilding to be used as a office on a farm. The supply is from a 3ph DB with PME supply in barn. Sub main 60metres. Not aggrecultual and live stock not in this area so tracktor will excavate. No Probs!!

Do I 2core and TT the outbuilding or 3 core and export the PME. What about RCD protection to the SWA sub main. Seems to be a lot of confusion and would very much appreciate feedback as qoute is urgent.:o

Link to comment
Share on other sites
 

Recommended Posts

Just remember if you do export a pme earth and things go wrong it will be your fault and you will be liable. If you read the suppliers literature its says you should not, I know this is mainly if there is services in the other building but I personally will not export a pme earth and usually not on tt or tns unless it is really awkward to get a rod in. Also you can get away with using twin armoured and use the steel as your cpc which on a long run can save a few quid. I think separate buildings should be kept separate from faults on the main building. This is the way I do it and will carry on that way.

Batty

Link to comment
Share on other sites
 
green-hornet
dont blame u. i have read some previos threads on this export pme they can get nasty

Nothing on this forum gets nasty:p

The reason we have these debates are to air an opinion, not everyone have their own.

We have to respect what each person brings to the debate, because that is what they have been taught or have been led to believe.

It is only through debate and questions that other opinions are aired and listened to.

Your never too old to learn, and something another person says may have some good resoning behind it.

The fact that we discuss these matters would imply that we all like to do things safely which after all is what we all want anyway.

The regulations are a guidline and are not enforced by law, therefore everything in the brb can be ignored, providing that what you do is no less dangerous, and as safe as, you would expect following all the guidlines.

However upsetting the Don! Now that can be nastyROTFWL

Link to comment
Share on other sites
 
SPECIAL LOCATION
..............However upsetting the Don! Now that can be nastyROTFWL

Now I heard that KME upset the Don..

so the Don put him in a coffin for 6months until he appologised....

but that was just what Apache told me!!!

Link to comment
Share on other sites
 

for the love of God TT it................

:)

Link to comment
Share on other sites
 

what is the facination with TTing things? Ive noticed everyone loves it. how comes?? :)

Link to comment
Share on other sites
 

Have you both read the huge exported earth threads for a start?

The gist is if there is a fault and your outbuilding has a lower resistance to earth than the PME supplied then all your fault current goes down the SWA to the outbuilding, and worse case scenario all your neighbours fault current too. Could be many 100's of amps - worse case. The earth out to the outbuilding then melts.

With a nice earth rod you have your own earth - nowt is shared etc. Much more reliable.

:D

Them that are real electricians can tell us more.

Link to comment
Share on other sites
 
 
NozSpark

They should never have supplied a farm with PME in the first place........................

Link to comment
Share on other sites
 

I seem to be getting to grips with this and appreciate feedback. It makes sence. But why do suppliers prefer PME. Is it the cost of cable or somthin else??

Link to comment
Share on other sites
 
Great. Yeah. TT the way to go. So why have DNO's gone down PME path???

I have no idea? Cheap?

Why did we chose VHS over the superior Betamax?

By reading threads on here TT seems to scare some of the newbies as they don't seem to have done as much on it as PME. TT seems simple to me.

Now I realise the benefits I wish I'd not let the sparky who changed my CU change us over from TT to PME :(

Link to comment
Share on other sites
 
 
NozSpark

You have to ask the question,,, is it a farm or not???

If it is then you need to read the special installations (section 70x) of the regs

Link to comment
Share on other sites
 

Im back. Just let the dog out and topped up my glass. I would say NO it is not a farm now. Where would I earth the armour at. The PME end or the TT end. And what about RCD protection to the said cable.

Link to comment
Share on other sites
 
Im back. Just let the dog out and topped up my glass. I would say NO it is not a farm now. Where would I earth the armour at. The PME end or the TT end. And what about RCD protection to the said cable.

AFAIK SWA needs no additional protection.

Earth the SWA at CU and isolate at the outbuilding.

Link to comment
Share on other sites
 

Fanx all. Have a look in every now and then when I have time. Great site . Keep up the good work. Rules and regulations are for the blind obedience of fools and the guidence of wise men.

Link to comment
Share on other sites
 

the against arguments for pme are not understanding how pme is provided.

how a pme at the end of a line of pme installations has less protection than the first is beyond me

i can think of a scenario where the first would have a higher ze than the last

Link to comment
Share on other sites
 
 
Have you both read the huge exported earth threads for a start?

The gist is if there is a fault and your outbuilding has a lower resistance to earth than the PME supplied then all your fault current goes down the SWA to the outbuilding, and worse case scenario all your neighbours fault current too. Could be many 100's of amps - worse case. The earth out to the outbuilding then melts.

With a nice earth rod you have your own earth - nowt is shared etc. Much more reliable.

:D

Them that are real electricians can tell us more.

Hurray a short version of some very long threads Applaud SmileyApplaud SmileyApplaud SmileyApplaud Smiley

Link to comment
Share on other sites
 
Andy™
what is the facination with TTing things? Ive noticed everyone loves it. how comes?? :)

for a start, he did say the supply was on a farm, and as you should know, TNCS & animals dont go together.

Link to comment
Share on other sites
 
Andy™
So why have DNO's gone down PME path???

cost over safety. its cheaper to run 2 cores, with same for neutral & earth, than it is for 3 core (TNS).

Link to comment
Share on other sites
 

And here I was expecting a mass argument again - `Pache is getting REALLY good at this paraphrasing jobbie.

Oh yes........Afternoon all!

Link to comment
Share on other sites
 

I understand what you are saying about this situation and TT and agree. However I am transporting the earth to domestic outbuildings, garages and the like, as I have seen too many rods not connected, for various reasons. If the earth is disconnected on PME systems nowt works as the neutral has also gone.

Link to comment
Share on other sites
 

That`s all well & good; but it DOES create an isuue with the earth conductor carrying vast amount of current; which is why there is a specific reg. for TT`ing outbuildings.

You don`t HAVE to agree with or follow the regs, as long as you can prove that YOUR method was at least as safe. Exporting PME earth is not safe. FACT!

KME

Link to comment
Share on other sites
 
 
There is an allowance in the regs for exporting earths be they TT or TNCS.

Where?

Strictly is it possible to export TT? You could rod either end.

Link to comment
Share on other sites
 

Archived

This topic is now archived and is closed to further replies.

×
  • Create New...

Important Information

Terms of UseWe have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.