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!

 

[kmcgold]

same has napits

 

[DurhamSparky]

cheers..!! should dispel the myths hopefully!!

 

[Sparky Ninja]

same has napits

I expect that 'Napits' is the same as the IEE on this occasion.

 

[IQ Electrical]

I expect that 'Napits' is the same as the IEE on this occasion.

Quite

 

[Sintra]

Stuck.......

 

[andyb]

cheers..!! should dispel the myths hopefully!!

I doubt it

 

[SimpleSimon]

Good article, but what are the myths?

 

[IQ Electrical]

Good article, but what are the myths?

The biggest myth is 'whoa, you can't export PME'.

Then there's 'if there are extraneous-conductive parts in the outbuilding, you can't export PME.

Then there's 'you must inform the DNO'

There may be more but the exported PME threads normally crop up here on at least a weekly basis and I think I can hear the groans of many members as the myths are propagated again and again!

These contentious issues should be periodically addressed/updated by the IET.

The last guidance on high protective conductor current was published in 2005 and even Guidance Note 8 has still not been revised to reflect 17th edition changes!

Not good enough.

 

[SimpleSimon]

Must admit I fell for the contact DNO one a minute ago.
I've never understood where this 'can't export PME' stuff has come from, it's all pretty straightforward if you know your stuff.
If exporting the earth bond back to the MET, if not TT and use your MET in the DB board.
I know there can be more to it, but that's the basis.

 

[DaveyD]

The biggest myth is 'whoa, you can't export PME'.

Thanks, but some of us have been taught that the DNO will not accept that on a TNC-S system. I am not trying to be contentious here but wonder where that myth came from.
Kindest Regards
David

 

[IQ Electrical]

Thanks, but some of us have been taught that the DNO will not accept that on a TNC-S system. I am not trying to be contentious here but wonder where that myth came from.
Kindest Regards
David

I think it was an amalgamation of the reg's pertaining to farms and caravans.

 

[DaveyD]

I think it was an amalgamation of the reg's pertaining to farms and caravans.

Right, thank you.

 

[james king]

im confuzled here wat is ment by export PME as in u can not take an earth from the main CU? u have to add a rod?

 

[IQ Electrical]

Basically, yes, have a look at the attached guide for better explanation.

 

[james king]

cant c it on my phone sorry!! as far as i am aware u can take a supply from a existing house CU via a MCB then to another sub CU ran in SWA. if the supply to the house is PME why would u need to put a earth rod in? can u not run a 3core cable and take the earth from the MET in the house??? i think i have miss understood

 

[IQ Electrical]

You can but there are reasons (often economic) why TT might be used, the point is, you have a choice.

Have a look at the guide when you''re at a pc.

 

[james king]

ok i am guessing a rod would be used for earth metal parts eg framework? could you use a rod conbined with the earthing from the house CU?

 

[james king]

can u please suggest some reason why u would use both ?

 

[IQ Electrical]

Perhaps where main protective bonding conductor sizing results in a completely uneconomic CSA of swa cable for the distribution circuit.