A good guide For 'exported PME' and outbuildings!

[sparkess]

Cheers for that, I hope I don't sound like an idiot, but at what point does the Zs change the choice of circuit breaker. It's a TT system by the way.

 

[malcolmsanford]

I think we are now entering the realms of competency here ....................... I will hand you over to my learned friends I think

You are not talking circuit breaker but RCD protection, but even if not then the type of circuit breaker is very relevant and is certainly linked with Zs values.

 

[sparkess]

Ah, just noticed all the other replies, sorry guys, my first time here. Yes I am an electrician, qualified 2yrs ago but this job isn't my usual bag. Yes the cable does require RCD protection as it will be supplying power for outdoor use. The installation in the barn is entirely fitted in conduit.

 

[sparkess]

...swa

 

[IQ Electrical]

Ah, just noticed all the other replies, sorry guys, my first time here. Yes I am an electrician, qualified 2yrs ago but this job isn't my usual bag. Yes the cable does require RCD protection as it will be supplying power for outdoor use. The installation in the barn is entirely fitted in conduit.

That in itself is not a requirement for RCD protection of a distribution circuit.

 

[casio200]

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?

Yes tell me where do myths come from ...... confuzled

 

[swifts]

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.​

 

[Engineer54]

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.​

From bias lectures that don't like PME earthing!! That seems to be one of the biggest influences anyway!! Same goes for RFC's, Using the Armour of SWA cables as the circuits CPC, and a few others too boot as well...lol!!

 

[Knobhead]

From bias lectures that don't like PME earthing!!

Don't understand more like!

 

[kevin55509]

thanks kevin55509

 

[jamie-spark]

What another cracking thread. So in summary so I can go forward,

1) We can export if practicable, if not TT it with all the usual requirements.

2)If we do export then a 10mm Main bonding cable must be provided, if services enter the location

3) If the CSA of the supply cable is <10mm we must provide a separate Main bonding conductor of 10mm

4)If the supply cable CPC CSA is > 10mm or + we can use said CPC as our 10mm main bond


Have I missed anything ?

My understanding from gn8 IS your exported bonding coductor size is the same as you bonding conductors for your main installation so if your main bonding is 50mm then your bonding to your outbuilding/shed will be 50mm even if your supply conductor size is only 16mm(to the out building)

 

[Jimmy Boy]

I have GN8 on back order from Amazon can't wait to get my nose in it..sad ain't i....
The was a time I would have a crumpled copy of Mayfair or Penthouse rammed down the back of the toilet systen..now it's electrical pawn lmao

ATB J

 

[IQ Electrical]

My understanding from gn8 IS your exported bonding coductor size is the same as you bonding conductors for your main installation so if your main bonding is 50mm then your bonding to your outbuilding/shed will be 50mm even if your supply conductor size is only 16mm(to the out building)

Yes, the main protective bonding conductors on a PME system are sized in accordance with the SUPPLIERS neutral conductor (not the tails) and as you rightly say, there is no provision to reduce the size in a distribution circuit to another building with main protective bonding requirements.

 

[MKS]

Excellent posting!!! What some don't realise, choose not to understand re: Myths

 

[Dan]

I'm just bumping some of the older threads in the general electrical forum that had a lot of replies. They might not be current topics, if they're not, just ignore them and they'll soon drop off the list. If you DO wish to add a reply and get the conversation going again, feel free to do so. Your input might help somebody else in the future.