16mm Earth main protective conductor

[Sav]

Hi everyone,

Just a quick question I hope I can get some advise on.

Saw a 1 bedroom purpose built 1st floor flat last night that is in need of a rewire.

The consumer unit is the old rewire-able type with 16mm T&E on supply side.
Although its red and black on the 16mm, it does look newish (10 years may be), but obvious tests will need to be carried out.

In the basement, which the customer does not have access too ( my FP2 key does not fit either, as it has some kind of security lock), I would have presumed there must be an isolator to this flat, as well as the other 5 flats on this block.
Again, this would need examining when the time comes.

I mentioned to the builder who is going to be carrying out building works, that we must check and upgrade the earthing accordingly, and also bring a 16mm earth to the consumer unit.
His guy, who also does electrics, said that the 16mm T&E along with its 6mm earth is more than adequate.

I have always bought in 16mm earth to the consumer unit, as thats what we were told to do on sites etc.

Am I missing something???

Thanks and regards,
Sav

 

[Sav]

Your builder is right , as a sub-mains to the flat , the earth in the T&E cable is fine.
The only earth that needs to be 16mm is the conductor from the MET to the switchgear at the supply position.

Thanks Biff and sorry again if I didnt explain myself properly.
So just to confirm, 16mm from MET to isolator (which I presume there is one).
Thanks again and have a great weekend,
Sav

 

[Geoffsd]

The apartment wont need a protective bonding conductor unless the water or gas mains enters the building in this flat.

Post isn't about bonding but each flat should have its own bonding to where the supply enters the flat.

 

[Guest55]

Post isn't about bonding but each flat should have its own bonding to where the supply enters the flat.

But he doesnt need to run a separate 16mm earth to each flat to do that , which is what Sav was suggesting.

 

[Geoffsd]

But he doesnt need to run a separate 16mm earth to each flat to do that , which is what Sav was suggesting.

I didn't say he did.

You said

"The apartment wont need a protective bonding conductor unless the water or gas mains enters the building in this flat."

which is wrong.

 

[Guest55]

no im not lol.
what your suggesting is supplementary bondng , the protective bonding to the gas and water mains has to be connected back to the MET , which wont be in the flat.

 

[PC Electrics]

The cpc in the distribution circuit must be sized for the most onerous requirement to be made of it. Now if this DC was supplying a garage with no other services then the 6mm cpc in the t&e would be perfectly adequate as it would be fed from a 63A MCB or an 80A fuse.

However, each flat is a seperate dwelling in this instance and will have other services (defo water and maybe gas). These will need main protective bonding within each dwelling. It is common to bond these services back to the flat CU. If the supply in the basement is TN-C-S / PME, then the bonding must be 10mm back to MET, thus the 6mm cpc will not be adequate. In this case a parallel 10mm will be required.

If the supply is TN-S, then 6mm meets the minimum basic requirement.

In addition, guidance is that the bonding back to MET must be no more than 0.05 ohm. If the flat is several floors up and so the earth conductor is long, then 16 or even 25mm may be required.

IMO it is not accpetable to bond each flats services directly to the MET in the basement, though I know some believe it is.

 

[Geoffsd]

Biff5.

I'm not suggesting anything.

You said

"The apartment wont need a protective bonding conductor unless the water or gas mains enters the building in this flat."

which is wrong.

However, each flat is a seperate dwelling in this instance and will have other services (defo water and maybe gas). These will need main protective bonding within each dwelling. It is common to bond these services back to the flat CU.

 

[Guitarist]

Think you need to get access to the supply mate, then all the conjecture can stop.

 

[Guest55]

The cpc in the distribution circuit must be sized for the most onerous requirement to be made of it. Now if this DC was supplying a garage with no other services then the 6mm cpc in the t&e would be perfectly adequate as it would be fed from a 63A MCB or an 80A fuse.

However, each flat is a seperate dwelling in this instance .
.

But with a shared gas and water main.
Which will be bonded as it enters the building , back to the MET.
And it still wont need a 16mm earth to each flat , which is the point ive tried to make all along.

 

[Geoffsd]

This is important:

You said

"The apartment wont need a protective bonding conductor unless the water or gas mains enters the building in this flat."

which is wrong.

Each flat will also need its own bonding from where the services enter the flat to the flat's MET.

But with a shared gas and water main.
Which will be bonded as it enters the building , back to the MET.

And it still wont need a 16mm earth to each flat , which is the point ive tried to make all along.

Then you shouldn't have called it ​bonding​ nor mentioned the water or gas mains.

 

[Guest55]

The flat wont have a MET , that will be in the basement at the supply position.

And you keep saying im wrong but without producing any facts to support your own statement ?

And why shouldn't i have mentioned the gas / water services ?

Your posts make little sense to be honest.

 

[spark 68]

The

flat wont have a MET , that will be in the basement at the supply position.

No, but it will have an EMT (Earth Marshalling Terminal) in each CU, and as each flat is classed as a seperate installation in it's own right, and this requires it's own local main bonding in each installation (read premises) as per 544.1.2 (BGB).

This is stated specifically in GN8 although the reg number given in GN8 is 537-02-01, as this book is now out of date but until the new updated version comes out this is all we have.

 

[Engineer54]

The flat wont have a MET , that will be in the basement at the supply position.

And you keep saying i'm wrong but without producing any facts to support your own statement ?

And why shouldn't i have mentioned the gas / water services ?

Your posts make little sense to be honest.

I'm afraid you are WRONG!! Each apartment /flat is considered a separate installation, which WILL require it's own bonding arrangements from the flats EMT to both gas and water, and any other extraneous service that enters the apartment/flat. That requirement is regardless of any bonding arrangements at the basements supply position MET...

There is a similar thread running at the moment, i think you NEED to read it, as well as BS7671 and the appropriate Guidance Notes!!!

 

[Guest55]

The

No, but it will have an EMT (Earth Marshalling Terminal) in each CU, and as each flat is classed as a seperate installation in it's own right, and this requires it's own local main bonding in each installation (read pemises) as per 544.1.2 (BGB).

This is stated specifically in GN8 although the reg number given in GN8 is 537-02-01, as this book is now out of date but until the new updated version comes out this is all we have.

Thanks for providing this info and for clarification.
Although classing each flat as a seperate installation when there is only 1 DNO supply , only 1 gas main and only 1 water main is open to debate in my mind.

 

[tony mc]

The

No, but it will have an EMT (Earth Marshalling Terminal) in each CU, and as each flat is classed as a seperate installation in it's own right, and this requires it's own local main bonding in each installation (read pemises) as per 544.1.2 (BGB).

This is stated specifically in GN8 although the reg number given in GN8 is 537-02-01, as this book is now out of date but until the new updated version comes out this is all we have.

Thats the problem with GN8 it takes a while to find out what the new reg number is!