another exporting earth thing

[maguire]

Can any one give me definitive on exporting earths, say PME and a supply to an outbuilding what the difference between a outside socket for lawn mowers strimmers etc spured off a convienient ring and a CU in a garage with one ring and lights taken from the main CU and taking the earth line and neutral to the shed, and the same with TNS, TT depending where the spike is either use that or sink another if distance is an issue
Your thoughts ?

 

[holmslaw]

..

 

[maguire]

Absolutly brilliant Holmslaw I thought I had seen this elswhere but thought I had dreamt it, really definative thanks again
DM

 

[holmslaw]

..

 

[LoveRocket]

You can export away to your heart's content (as long as the DNO don't mind). The only requirement is that if on a TNCS supply and the outbuilding has extraneous conductive parts, you MUST bring a main bonding conductor out too, thus extending the equipotential zone.

 

[maguire]

Love rocket H,i thats the bit I do not quite get (I have still to read the IET notes that Holmslaw pointed out) why the need for a seperate conductor surely in the case of extraneous stuff that will be bonded anyway, and the outbuilding main earth will return to supply source, bonding the two together seems overkill and is that really bonding is it not just an additional earth conductor, I mean my house is not bonded to next doors
DM

 

[LoveRocket]

All it means is that all extraneous conductive parts in the outbuilding must be bonded back to the MET - just as all extraneous conductive parts in the house must be. In most TNCS cases, 10mm MPB conductors are used, so you must also use a 10mm MPB conductor to the outbuilding too.
The IET do say this can also be the earthing conductor, so if you are running 10mm (or bigger) 3core SWA out to a garage, you can use a core as the CPC and MPB conductor.

Hope that makes sense!

In reality it means that if you have a garage with a copper water main coming in to it, you can't just run a 2.5mm cable out there and bond the waterpipe to the CPC, you MUST use a 10mm main bonding conductor back to the MET in the house. With 10mm+ submains it's not a problem - although then you get in to 'unbroken bonding conductors'

 

[maguire]

Hi yes rocket your 1st response was, at 2nd reading quite clear after I read it properly, sorry I sometimes confuse myself with preconcieved ideas putting conclusion before asimilating the info
DM