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

 

[Top Cat]

Wow! I was going to reply to original post but i don't think i will now after all the arguments!

 

[spark 68]

I have added the two pages from GN8 to my previous post #27 to clarify

 

[Guest55]

So , taking onboard recent comments....
What size should this protective bonding conductor in the flat be ?
Just out of interest ...

 

[tony mc]

At the moment we do not know the earthing arrangement of the premises.

If its PME then table 54.8 comes into play re the bonding and if TNS or TT the csa should be not less than half the csa of the required earthing conductor with a min of 6mm!

 

[spark 68]

According to GN8, the main bonding is sized to the DNO's incoming Neutral supply cable, not the downstream local neutral supply cable to the individual flat, it should not be less than 35mm in the case of PME supplies.
It is a little odd in the the main bonding conductors can have a greater csa than the local Live supply (to each flat CU) conductors.

In all other cases (TT, TNS) the main bonding is sized to be not less than half of the Earthing conductor.

At least that is how I read it (GN8).

 

[Engineer54]

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.

NO, ... There is nothing to debate at all!!

 

[Guest55]

At the moment we do not know the earthing arrangement of the premises.

If its PME then table 54.8 comes into play re the bonding and if TNS or TT the csa should be not less than half the csa of the required earthing conductor with a min of 6mm!

Agreed , but table 54.8 applies to the main protective bonding ,which is in the basement , where the gas and water services enter the building.
Not relevent to where the services enter each flat.
Unless your suggesting that there needs to be 2 sets of main protective bonding conductors , basement and flat ?


I do like a healthy technical debate lol.

 

[Guest55]

NO, ... There is nothing to debate at all!!

A very narrow minded view you've got there.

 

[spark 68]

But each flat has it's own main bonding requirement.

I will be glad when the new GN8 comes out, as it is a nightmare trying to marry up the 16th ed reg no's with the current regs.

 

[spark 68]

To Add,

If each flat is PME, the earthing conductor to each flat has to be a minimum of 35mm, (again sized to the DNO's incoming Neutral), as it has to satisfy as a combined CPC and main bonding conductor (Pg 52 GN8).

 

[Engineer54]

This is getting to be like pulling teeth...lol!!

Every flat, (be there 2 or 20 flats) will each require a main protective bonding installation, REGARDLESS of the main protective bonding arrangements made at the buildings service head and main distribution centre and where the main services enter the building (eg, gas & water).

 

[tony mc]

Agreed , but table 54.8 applies to the main protective bonding ,which is in the basement , where the gas and water services enter the building.
Not relevent to where the services enter each flat.
Unless your suggesting that there needs to be 2 sets of main protective bonding conductors , basement and flat ?


I do like a healthy technical debate lol.

Main protective bonding conductors are required in every flat in Multi Occupancy Premises regardless to what is connected outside that premises!

 

[Engineer54]

A very narrow minded view you've got there.

Really, perhaps you can tell us what's narrow minded about following requirements??

And if you think about it, why it's a requirement!!!

 

[Guest55]

To Add,

If each flat is PME, the earthing conductor to each flat has to be a minimum of 35mm, (again sized to the DNO's incoming Neutral), as it has to satisfy as a combined CPC and main bonding conductor (Pg 52 GN8).

But the flats aren't pme , tt , tns or anything else , they're supplied via a privately
owned sub-mains ? so not entirely relevent.

 

[Guest55]

Really, perhaps you can tell us what's narrow minded about following requirements??

And if you think about it, why it's a requirement!!!

I didnt say the requirements were narrow minded , just your view that an wider issue cant be discussed openly.