Upgrading meter tails and main earth for a C/U change

[D Skelton]

If TNCS then i would have thought your assessor will be looking for 16mm earthing conductor in case of a lost neutral on the suppliers network.

And why would the method of supply dictate the size of the main earthing conductor???

Apologies, I thought my OP mentioned it was a PME supply, but I hadn't.

It is of no consequence what the method of supply is, your main bonding conductors are 10mm so all you need is an adiabatic to confirm that the csa of the main earthing conductor is adequate.

Because that was what I was taught and have been told by others electricians - if you change the board, you need to make sure that tails are 25mm and earth is 16mm to meet 17th Ed requirements. If that's not the case, then fine - lesson learnt!

Forgive me if I sound a bit harsh here but you would only have been taught this on a Electrical Trainee course, hence my hatred of the people who peddle these useless courses to the masses as all they do is preach myth and here say. I can assure you that no electrician would have told you that this is the case because real electricians can differenciate between the OSG and the BGB.

If I'm wrong, forgive me, but if I'm right and you're a Electrical Trainee yourself I would heavily recommend you spend the next few weeks taking your BGB to bed and spending a couple of hours a night on some bed time reading. Personally, I believe that a front to back knowledge of the BGB combined with the understanding of the type of circuits you are working on is all you need to be a good electrician.

 

[power ranger]

Putting meter tails on a 100mA time delayed RCD does not make it comply.

cables buried in walls as mentioned always need 30mA RCD protection....but its better than before

Thanks spartykus,
I never picked that one up last (well it was late on a friday night!)

Yes 30ma rcd for buried cables in plaster etc.

 

[trev]

Thanks to all for your comments/suggestions

Apologies, I thought my OP mentioned it was a PME supply, but I hadn't.

Building work was finished about 6mths ago, not entirely sure what was done though. Nothing further happening, and max load not increasing from current demand.

Trev asked why I thought the tails and earth needed upgrading? Because that was what I was taught and have been told by others electricians - if you change the board, you need to make sure that tails are 25mm and earth is 16mm to meet 17th Ed requirements. If that's not the case, then fine - lesson learnt!

Wasn't having a pop at you mate (after I reread your OP ) merely trying to get you to think about the situation as it's better for you than having the answer handed to you on a plate. See E54's post re the need for 25mm tails v 16mm ones.

 

[The General]

Thanks to both of you - that explains a lot of the misunderstanding!
Cheers for the advice.

 

[telectrix]

and just to clarify. if the existing meter tails are buried<50mm, you do not have to fit RCD to protect them. you only need to do this if you fit new tails. that's because regs. are not retrospective.

 

[SPARTYKUS]

and just to clarify. if the existing meter tails are buried<50mm, you do not have to fit RCD to protect them. you only need to do this if you fit new tails. that's because regs. are not retrospective.

...otherwise every 2 hour job would end up taking 3 months. Unpaid.

 

[Niceguy0584]

Hi All

I am new to this site, and was wondering if you can guide us to the right direction, I am doing EICR's and I have come across flats which are wired from submains with 16mm2 TW&E and the cable run is about 12 meters protected by kfm 60amp switch, my question is this installation is over 20 years old and the earth from from submains 16mm TW&E is used, which is 6mm and is non compliance to current reg, my question is which code would this be classified as? C1 C2 or C3

Thanks

Adam

 

[D Skelton]

the earth from from submains 16mm TW&E is used, which is 6mm and is non compliance to current reg

Which reg is that then???

 

[telectrix]

at each sub-main, measure the PEFC. then apply the adiabatic. you will find that 6mm is adequate to carry the fault current for the period of time it takes tha 60A fuse to blow ( in most cases). if so, then no code.

 

[Richard Burns]

Hi All

I am new to this site, and was wondering if you can guide us to the right direction, I am doing EICR's and I have come across flats which are wired from submains with 16mm2 TW&E and the cable run is about 12 meters protected by kfm 60amp switch, my question is this installation is over 20 years old and the earth from from submains 16mm TW&E is used, which is 6mm and is non compliance to current reg, my question is which code would this be classified as? C1 C2 or C3

Thanks

Adam

I agree with the above, welcome to the forum.
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