Bonding Advice Needed

[Bolty2uk]

Hiya.
New to this great forum so firstly would like to say hi. Im not an electrician and dont confess to being technically minded but i do have a quandry so after some advice really.
Anyway. My question is this. In a building that has 5 seperate flats we have all incoming service heads at ground level then via a main switch and rcd a 16mm twin and earth goes to each flat where the sparky will fit new boards to serve each flat. Now as im a builder organising all this i need to make sure all the plumbing and electrics are in place before i start putting in dropped ceilings and studwork etc..

Now question is in each flat there will be metal pipes to heating and water etc and i would assume they need bonding.
Now. The sparks has told me he is happy to run 16mm earth to main incoming water and gas from main earth block where incomers all are near front downstairs. So in effect no extra bonding in each flat.
But another guy we use said we need to run 6mm earth from the earth block in the fuse board in each flat to all the metal stuff in that flat in addition to what first guy said.

Now to save a barney and me a job of having to rip up floorboards later on does anyone know who is right. My money is on second guy but the lad we always use is positive and its all getting a bit hassly lol.
Anyone have any thoughts.
Many thanks for and replies i might get.
Thanks

 

[Octopus]

6mm - not sure that's right!

 

[Bolty2uk]

6mm - not sure that's right!

Yes. I agree. Ive worked before with a gas guy and a sparks and they used 10mm i think. But that was a house. So both are incorrect lol. Nightmare

 

[Octopus]

Maybe ask a 3rd spark...

 

[Bolty2uk]

Maybe ask a 3rd spark...

Yes. That is what i will be doing. I just though two electricians would provide the same answer. If the next guy gives another answer i will report back and give up. Its a crazy situation and i feel like a peacekeeper lol

 

[davesparks]

The size of the bonding will depend on the size of the incoming supply from the DNO (electricity board), who may even specify the size required above what the wiring regs call for.
In the average house main bonding will be 10mm, in small blocks of flats 16mm is not unusual.
Bonding should be applied to extraneous parts, this means any metal which brings an earth potential in to an installation, this includes service pipes, lightning conductors, structural steel, air con ducting.

There should be main bonding at the point of entry to the building as a whole of each extraneous part.
Also there should be main bonding at the point of entry to each flat of each extraneous part.
All of this bonding must be of the correct size for the incoming supply, I'll assume this should be 16mm in this case as you've mentioned it already. So that means that it needs to be 16mm from the intake to the services entering each flat.
If there is only 16mm T&E running to each flat then the earth in it (6mm) is not big enough for bonding and an additional 16mm earth is required.


You also need to be aware that having an RCD at the incoming position covering each flat does not comply with the regulations, the installation in each flat needs to be divided across multiple rcds. This will likely mean that the 16mm T&E will need to be replaced with armoured cable or have additional metal protection fitted to it.

 

[davesparks]

Yes. That is what i will be doing. I just though two electricians would provide the same answer. If the next guy gives another answer i will report back and give up. Its a crazy situation and i feel like a peacekeeper lol

There are far too many electricians out there who would rather believe rumours and old wives tales or just haven't kept up with the current regulations.
The guy who wants to just install main bonding at the incoming positions is likely misunderstanding the regulations.
The guy who wants to install 6mm bonding is probably still applyjng the requirements of the 16th edition wiring regulations which were replaced by the 17th edition in 2008.

 

[Octopus]

Yup... ^^ agree 100%.

Using twin and earth from the incoming supply to each flat would not meet the regs and just imagine the residents having to go the incoming supply each time the RCD trios....

 

[Bolty2uk]

There are far too many electricians out there who would rather believe rumours and old wives tales or just haven't kept up with the current regulations.
The guy who wants to just install main bonding at the incoming positions is likely misunderstanding the regulations.
The guy who wants to install 6mm bonding is probably still applyjng the requirements of the 16th edition wiring regulations which were replaced by the 17th edition in 2008.

Thank you very much Davesparks.
So i do have a nightmare as i expected.
I did actually say to the first guy was the rcd down near incomers needed as when he fits the new fuse board if the light which are not on rcd side of new board go wrong it will take flat out i guess.?
Well im going to have to seek more advice as neither have suggested that the supply cable isnt good enough. Or that a seperate earth was needed. This doesnt fill me with confidence. Ive used the first guy for about ten years. And this probably isnt best place to say it but the plumber normally pulls me up and picks up things.

 

[Wilko]

You need a coordinated design, and now is the time to do it. Likely the feeds should be upgraded to SWA cable. Have you thought about fire alarms?

 

[Bolty2uk]

Yup... ^^ agree 100%.

Using twin and earth from the incoming supply to each flat would not meet the regs and just imagine the residents having to go the incoming supply each time the RCD trios....

Thanks Murdoch for taking time to reply too. I cant believe im here asking for advice but it didnt seem right to me. And these guys would have given the owners all certificates too..

 

[Bolty2uk]

You need a coordinated design, and now is the time to do it. Likely the feeds should be upgraded to SWA cable. Have you thought about fire alarms?

Hi Wilko. Yes. That is something that i feel has been done right. Hallway lights, firealarm, and ariel booster in loft come off a small landlords supply and last week all the red fp cable was put in place. 6 zones. In light of things no expense.
The quandary is the electrics.

 

[davesparks]

Thank you very much Davesparks.
So i do have a nightmare as i expected.
I did actually say to the first guy was the rcd down near incomers needed as when he fits the new fuse board if the light which are not on rcd side of new board go wrong it will take flat out i guess.?

The lights will almost certainly need RCD protection, again this is something which changed in 2008 so there is no excuse for being out of date with the regulations.
But as you have worked out there should be multiple RCDs to minimise the amount of the installation which loses power when one trips.
The ideal option is to have each circuit protected by an RCBO, this is a device which combines the functions of an MCB and an RCD in to one unit. This keep every circuit completely separate.

 

[Bolty2uk]

You need a coordinated design, and now is the time to do it. Likely the feeds should be upgraded to SWA cable. Have you thought about fire alarms?

Yes. I agree. I need a company with a design team. Not a one man band. I just thought they would all provide the same answer lol

 

[davesparks]

Yes. I agree. I need a company with a design team. Not a one man band. I just thought they would all provide the same answer lol

I wouldn't be too quick to knock the one man bands, some of us know what we are doing