Export PME or not that is the question?

[SYKRAPS]

So guys I know that this is a frequentley asked question but which way would you do it?

The building that requires power installing has extraneous parts by the way.

Would you.

1. Devorce the PME earth from the house and install a spike.

2. Use the PME earth from the house within your supply cable and run a seperate 10mm earth from he MET to the extraneous parts.

For your information the cost implications are virtually identical.

Regards.

 

[Silly Sausage]

I'd go for No. 2
Don't have to mess around with rods (or twigs!) and 'dodgy' Ra values!

 

[keniff]

Or could you use a 10mm armoured or bigger then i think there is no need for separate earth cable

 

[Engineer54]

Depends very much on how far away from the original supply this building is, and whether this is a farm building that will be housing animals etc?? ...I'll assume for now then, that the distance isn't excessive, and that no farm animals etc will be housed in this building.

Generally speaking, i would normally extend the PME's equipotential zone, and retain the TN Zs values. As this new building has extraneous parts, you will need to run in a 3 core 10mm SWA or a separate 10mm CPC with a smaller sized SWA cable. If that's the case, it would be better if the cables run was in a protective duct...

 

[Phillcbr400]

You're going too be digging anyway for the supply so go with no.2. Always good practice to include ducting with buried works.

 

[telectrix]

nothing to add. all been answered.

 

[SYKRAPS]

Hi guys and thank you for your replies.

My way after discussion with the client was also in line with method 2.

The building is to be used as a very small home workshop and the cable run is circa 18m.

The way that we decided to perform the work was with a 10mm 3 core swa and a 10mm g/y running within a burried duct (duct pre installed by the client to prescribed guide lines from myself) fused at 32 amps at the origin. Overkill with the 10mm g/y i know but for an extra £10 ish i prefered to be over the top. No livestock within the building so just a few lights on a 6a circuit and a few sockets on a 16a circuit.

Thanks again for the response.

And I must say a very short and concise exporting PME or not thread with no disagreements

 

[telectrix]

you don't need that separate 10mm cpc if you are using 3 core SWA. use the 3rd core and the armour. more than adequate.

 

[Engineer54]

Agree with Tel, absolutely no need or requirement for a separate 10mm conductor to be run in with a 10mm 3 core SWA cable. It'll be a total waste of money and time. The 3rd core is your bonding conductor and the armouring your circuit CPC... Don't waste your customers money!!

 

[SYKRAPS]

Thanks tel & E45 i agree but I thought for the sake of about £10 (that the client was willing to pay btw) it would be better seen as though the isolation for the outbuilding was fed with a 10mm t+e within the house and I wanted to run a clean 10mm g/y back to the MET.

Could have just run the 10mm g/y with the 10mm t+e to the isolation point I suppose

 

[Engineer54]

Thanks tel & E45 i agree but I thought for the sake of about £10 (that the client was willing to pay btw) it would be better seen as though the isolation for the outbuilding was fed with a 10mm t+e within the house and I wanted to run a clean 10mm g/y back to the MET.

Could have just run the 10mm g/y with the 10mm t+e to the isolation point I suppose

You will need that 10mm separate conductor from the house isolation point anyway!! If your connection of the 10 mm bonding cable is sound within the isolator enclosure, all is well ... Make it a butt through crimped connection, which will be even better!! lol!!!

 

[Deleted member 26818]

If you are intending to run a separate earth conductor, then there's no need for the 3core SWA.
Could use 2core instead.

 

[SYKRAPS]

Over the top I know but its done now

 

[davelerave]

if the outbuilding was much further away
what would be the problem with just creating a new equipotential zone with a 3core submain

as against extending it with a large main bond from met

i'm prob missing the obvious-i don't quite get the idea of extending the equipotential zone to a remote building