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!

 

[malcolmsanford]

you can export on a TNS SYSTEM IF TNCS TT ONLY OPTION

Surreal man ........................right on

 

[IQ Electrical]

Surreal man ........................right on

Why do I bother?

 

[swifts]

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.
​

 

[Engineer54]

This really needs to go back in the ''Sticky section'' above!! It seems that there are still far too many here, that have been brainwashed by the scaremongers into believing you can't extend a PME equipotential zone, or take a PME CPC with you to an outbuilding or shed!!

 

[Guitarist]

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.
​

There is a new edition out. Check Amazon mate.

 

[sparkess]

Hi, great thread - quick question... I'm installing power and light to a workroom in the back of a detached barn. Supply is off a spare way in the house and will feed a small consumer unit in the barn. The barn cu will have 30ma RCDs so my question is: Am I right to use a 100ma RCBO at the house so the whole thing doesn't automatically trip?

 

[malcolmsanford]

You can do that yes ..........................

But you may not need to, it will depend on what your earthing system is Ie TNC-S TN-S or TT and what your Zs will be for the distribution circuit

 

[Guitarist]

Hi, great thread - quick question... I'm installing power and light to a workroom in the back of a detached barn. Supply is off a spare way in the house and will feed a small consumer unit in the barn. The barn cu will have 30ma RCDs so my question is: Am I right to use a 100ma RCBO at the house so the whole thing doesn't automatically trip?

Also, there is a strong possibility that the 100mA at the house will trip at the same time as to 30mA in the barn. You will need a time-delayed (s-type) RCD in the house if you want to provide discrimination whilst protecting the supply cable. Not sure whether you are an electrician or not, so just to let you know, this job would be notifiable to your LBC.

 

[SW1970]

And what cable type and which installation method.

 

[IQ Electrical]

As Guitarist said, the 100mA device will almost certainly trip simultaneously with a 30mA device downstream-does this 'supply cable' actually REQUIRE RCD protection?

 

[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.