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Topic Title: Some feedback much appreciated
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Created On: 19 March 2013 09:16 AM
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 19 March 2013 09:16 AM
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earthing

Posts: 56
Joined: 17 December 2008

Hi,

Just rewiring a Bungalow with a TN-C-S supply.

Sorry for another post on garage supplies but I am not confident I answered the question myself last night. (After reading manyany previous posts)

I was going to TT the garage but then I discovered the gas supply is in the garage. Originally my design was to feed the garage supply with a 4mm armoured cable fed from an MCB (no rcd) supplying a dual MCB board with 30ma protection on the final circuits.

However after discovering the gas supply I am a little unsure what the safest solution would be.

After some research last night I felt it was safer to export the pme with a 3 core armoured cable to allow the 3rd core for bonding and a cpc.

Any help much appreciated.

Daniel
 19 March 2013 09:31 AM
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zeeper

Posts: 1409
Joined: 11 July 2008

This maybe of interest

http://electrical.theiet.org/w...outdoors.cfm?type=pdf

if you not already read it.
 19 March 2013 10:04 AM
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aligarjon

Posts: 2813
Joined: 09 September 2005

You could run a 10mm swa to cover the bonding although i seem to remember BOD rapping my nuckles a couple of years ago for using an earth cable as a bonding conductor. i wouldn't think that applies here.

i pressume this gas pipe is going to be bonded in the house as well ?


Gary

-------------------------
Specialised Subject. The Bleedin Obvious. John Cleese
 19 March 2013 10:14 AM
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earthing

Posts: 56
Joined: 17 December 2008

Ok Cheers guys.

The gas pipe is currently bonded in the house inside the attic which is roughly 1.2m from the gas meter.

I just spoke to NIC technical and they said it was fine to export the PME as long as the gas was bonded in the garage.

So I'm thinking now of running a 4mm twin and earth and a 10mm bonding conductor in to the garage. Garage fed off an RCBO and supplying a two way fuse board.

Always worries me as I failed my first Nic inspection because I exported the PME 95M via a 3 core 16mm supply cable to a mixed use building. Entertainment/horse stables.

Hhhmmm make what you will of mixed entertainment horse stable building!!
 19 March 2013 12:10 PM
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jcm256

Posts: 1856
Joined: 01 April 2006

Just rewiring a Bungalow with a TN-C-S supply.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
The supply is PME or TN-C it only becomes TN-C-S now called TN-C-S system when you separate the earthing from the neutral in the installation, the S can now added to TN-C what you now have is a supply PME and a system TN-C-S.
Just pulled you up because your name is earthing, you should have said PME supply.

Very good reference guide here: Many thanks to J P for authoring this guide.

This will give you guidance on exporting PME to outbuilding and the use of SWA as earthing conductor.

http://www.gadsolutions.biz/regulations/swa-as-a-cpc
 19 March 2013 12:54 PM
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AJJewsbury

Posts: 11349
Joined: 13 August 2003

The supply is PME or TN-C it only becomes TN-C-S now called TN-C-S system when you separate the earthing from the neutral in the installation, the S can now added to TN-C what you now have is a supply PME and a system TN-C-S.

Although you could argue that as the separation happens in the supplier's cut-out, and the supplier presents separate E and N terminals (one on the meter the other on the side of the cut-out) that it's already TN-C-S by the time BS 7671 starts
- Andy.
 19 March 2013 12:59 PM
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AJJewsbury

Posts: 11349
Joined: 13 August 2003

The gas pipe is currently bonded in the house inside the attic which is roughly 1.2m from the gas meter.

So presumably the garage is attached to the house?

If so, why not treat both as a single building and have one equipotential zone - run a 10mm2 from the house MET to the gas intake position in the garage (forget the one in the loft), and just have a basic submain to the garage CU (or not bother with a separate CU and just feed the garage electrics from the house CU).

- Andy.
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