Running PME (TNCS) outdoors?

[TheFullHitSpark]

Alright guys, ime racking my brains and books trying to find out why my boss told me that you are not supposed to run PME outdoors to say out feeding a garage or a shed of some sort, i know about potential differences.... also i know some about special locations but i just cant understand why your not allowed PME, surely if the cable is protected by an RCD, the same as it would be if you was using an earth steak for TT what is the difference?? can someone elaberate on this for me please. if this is the case you would have to have an earth steak which would be a seperate means of earthing than provided from your source, but obvioulsly your (PME) earth would still have to provide protection for the cable feeding the (sub main).

Thinking outloud abit..



If someone could show me the light i would be mostly appreciative.




Cheers guys, also as you all probably know this forum is the dogs go-nads...

 

[bateman585]

read the 17th edition, nickname ( the bumper book of fun ) pme or tn-c-s supports neutral, connot run live connductor outside of building, best way is run phase & neutral, to garage,
and put earth stake in for protection, only to garage consumer unit though, bit like a builders supply realy, but thats the reg's
i could explain in detail, but would take a long time

 

[IQ Electrical]

read the 17th edition, nickname ( the bumper book of fun ) pme or tn-c-s supports neutral, connot run live connductor outside of building, best way is run phase & neutral, to garage,
and put earth stake in for protection, only to garage consumer unit though, bit like a builders supply realy, but thats the reg's
i could explain in detail, but would take a long time

Where is this regulation? It has obviously been omitted from my copy of BS7671:2008 with corrigendum.

 

[SimpleSimon]

The only one I can recall is a PME supply shall not be run INSIDE a domestic premises.

 

[IQ Electrical]

The only one I can recall is a PME supply shall not be run INSIDE a domestic premises.

That reg refers to PEN conductors and is not restricted to domestic installations.

The PEN conductor only goes as far as the service head where it is separated!

 

[Deleted member 9648]

1. Apart from some special locations as defined in section 7 of bs 7671 there are no regulations in bs 7671 preventing a TNCS (PME) supply being used to supply external equipment and outbuildings.
2. The DNO dont give a ---- about exporting TNCS supplies as long as it complies with Bs 7671.
3. The reason regulations on exporting PME earths or separating for external supplies which are not a special location cant be found in the BRB is because they are not in there.
END OF.

 

[IQ Electrical]

1. Apart from some special locations as defined in section 7 of bs 7671 there are no regulations in bs 7671 preventing a TNCS (PME) supply being used to supply external equipment and outbuildings.
2. The DNO dont give a ---- about exporting TNCS supplies as long as it complies with Bs 7671.
3. The reason regulations on exporting PME earths or separating for external supplies which are not a special location cant be found in the BRB is because they are not in there.
END OF.

Ah, a pleasure to read......

 

[SimpleSimon]

That reg refers to PEN conductors and is not restricted to domestic installations.

The PEN conductor only goes as far as the service head where it is separated!

Does a PEN conductor form part of a PME?

 

[gamblor6]

lol wirepuller you REALLY hate this subject dont you.

 

[Deleted member 9648]

lol wirepuller you REALLY hate this subject dont you.

Whatever gave you that idea.........

 

[IQ Electrical]

lol wirepuller you REALLY hate this subject dont you.

Not as much as me, people just manufacture 'reg's based on rumour and opinion, it's pretty basic stuff in the scheme of things!

Guys use these threads to assist in their studies etc. so let's not make up regulations!

 

[IQ Electrical]

Does a PEN conductor form part of a PME?

Yes, up to the service head where it ceases to exist (it is separated).

That is the 'S' in TN-C-S

 

[gamblor6]

all threads on this subject roll merrily along until, i can tell, you.ve had enough

 

[SimpleSimon]

Yes, up to the service head where it ceases to exist (it is separated).

That is the 'S' in TN-C-S

I know. But I now know what I wad confusing the reg earlier with. As always IQ, thanks for your help

 

[pushrod]

The impression I get is that the presence of extraneous conductive parts does not preclude the use of an exported TNC-S earth, it mearly means that they have to be bonded back to the submain MET with the same size cable as is appropiate for doing the same in the main building, and that the same sized or bigger earthing cable is used to provide the earth to the submain board, and as this is not always practical, a way of avoiding having to install bigger cables is to convert the remote installation to TT, and bond extraneous bits back to this

I think!!!!!!

pretty much what i think too -and once you get to about 12M of 10mm bonding it gets cheaper to to put an earth electrode in unless there is some other complicating problem.

 

[Deleted member 9648]

Bang on.....but most of these threads are about sheds and garages with no extraneous conductive parts requiring main bonding.