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

 

[westward10]

It would be acceptable to connect the main protective bonds at the service head if that is their intention.
To use T&E without earthed containment for a sub circuit to each flat so it requires additional rcd protection is quite frankly ridiculous as division of circuits is lost immediately.

 

[ipf]

Yep, it's all about taking correctly sized supply plus correctly sized earth to each flat, then the bonding for each.
Your lad's correct about one thing...he'll still have to bond at building entry point, too. They're all taken as separate installations.

A bit of a full design by the right person might be the way to go.

edit. Sorry lads, a bit late with that.

 

[Bolty2uk]

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

Sorry Dave. Wasnt ment to come out like that. I truley appreciate your advice. Its clear you have a good understanding of this. It seems one or two things are wrong here and i need to find someone else. But my dilema is i dont know. And if i get another different answer im not sure who to go with.

 

[davesparks]

Sorry Dave. Wasnt ment to come out like that. I truley appreciate your advice. Its clear you have a good understanding of this. It seems one or two things are wrong here and i need to find someone else. But my dilema is i dont know. And if i get another different answer im not sure who to go with.

No worries.

Unfortunately the domestic market is flooded with less than competent electricians, particularly when it comes to designing an installation.

There's no hard and fast way to guarantee that the design you get is right, but you could look at paying to have the design work done as a separate job with full paperwork and specification provided for the installers to work to.

 

[Toneyz]

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.

I agree with Dave when we used to do flats it depends upon the other services sometimes the gas would come from semi concealed gas meters externally into each flat and would bond where entry into flat but would treat each flat as a installation with 16mm earth to consumer unit then 10mm to services then treat landlords installation separate bonding to each services unless plastic pipe.

 

[Toneyz]

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.

Depending upon the installation methods the RCD/RCBO additional protection could be omitted .

 

[davesparks]

Depending upon the installation methods the RCD/RCBO additional protection could be omitted .

Which is why I said ALMOST certainly will require RCD protection.
It is unlikely that the lighting circuits in a domestic installation will not require RCD protection these days.

 

[Baker1988]

As it is just a small flat I presume there will only be 1 lighting circuit in each flat and as there will be a light in the bathroom that lighting circuit will need to be rcd protected in accordance with reg 701.411.3.3 of amendment 3 which states:
"In specific locations such as those containing a bath or shower
there is a requirement now to provide RCD protection on
all circuits, including the lighting and shower circuits." so lighting will also need rcd protection in my eyes

 

[Toneyz]

It was more the sub-distribution circuit that I was referring to ( however my preference is SWA) 16mm T & E with additional earth when run in compliance the need for a upfront RCD can be omitted ,which is against the regs anyway. I remember from when I started as a apprentice always installing two lighting circuits in flats and bungalows etc.

 

[Mikeluker]

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

The main bonding would only need to installed within the gas floor boxes outside on the consumer side of the stop cock. The main water assuming this would be in the riser position would require a main bond only in the incomer position both sized in accordance to the main neutral. They won't require any additional bonding within the flat themselves as there are no other earth potentials being introduced. The submains to the flats will require a disconnection time of 5 seconds so no rcd will be required. Each flat would need rcds / rcbos internally split across lighting circuits etc as not to cause full failure if a fault occurs.
Normally if an underground extraneous pipe goes from one building to another both bonds would be required as to equalise both potential differences between them, I hope this helps.

 

[Simonslimline]

Edited

 

[Simonslimline]

The main bonding would only need to installed within the gas floor boxes outside on the consumer side of the stop cock. The main water assuming this would be in the riser position would require a main bond only in the incomer position both sized in accordance to the main neutral. They won't require any additional bonding within the flat themselves as there are no other earth potentials being introduced. The submains to the flats will require a disconnection time of 5 seconds so no rcd will be required. Each flat would need rcds / rcbos internally split across lighting circuits etc as not to cause full failure if a fault occurs.
Normally if an underground extraneous pipe goes from one building to another both bonds would be required as to equalise both potential differences between them, I hope this helps.

So do you know the earthing arrangement regarding the incoming neutral comment????

It might not be PME!

Also I was not aware that a DT of 5 seconds makes a circuit void of any RCD protection!!!

 

[Toneyz]

So do you know the earthing arrangement regarding the incoming neutral comment????

It might not be PME!

Also I was not aware the a DT of 5 seconds makes a circuit void of any RCD protection!!!

It dosn't

 

[Simonslimline]

It dosn't

This I what I was pointing out. Could of worded it better though to be honest.

 

[Mikeluker]

So do you know the earthing arrangement regarding the incoming neutral comment????

It might not be PME!

Also I was not aware that a DT of 5 seconds makes a circuit void of any RCD protection!!!

 

[Mikeluker]

Assuming pme of course

 

[Simonslimline]

Assuming pme of course

What about the RCD of the Distribution CCT!

Design of an electrical installation is not based upon assumptions.

 

[Mikeluker]

What about the RCD of the Distribution CCT!

Design of an electrical installation is not based upon assumptions.

Yes you are right, this is all we have to go on in the post. If the distribution circuit is from a pme source and the cabling is not buried within a wall less than 50mm then an rcd would not Ben required or am I missing something

 

[Des 56]

a 16mm twin and earth goes to each flat where the sparky will fit new boards to serve each flat.

Here is a couple of comments I would like to make regards the last few posts


The opening post does not say the cables are buried
Or if they are buried and mechanically protected
Or if it is the intention to have them in surface trunking


It may be the case that the regs can be interpreted to require main bonding only at the point of entry,however,each flat then relies on that main bond remaining intact to ensure the particular service remains bonded for their individual service
It would seem to be an improvement to ensure that each flat has its own means of ensuring main bonding is reliably bonded by doing so locally to each flat

Bonding at the Gas meter in the garden would extend the zone outside of the building,I think it needs fitting where the pipe enters the building

 

[davesparks]

a 16mm twin and earth goes to each flat where the sparky will fit new boards to serve each flat.

Here is a couple of comments I would like to make regards the last few posts


The opening post does not say the cables are buried
Or if they are buried and mechanically protected
Or if it is the intention to have them in surface trunking


It may be the case that the regs can be interpreted to require main bonding only at the point of entry,however,each flat then relies on that main bond remaining intact to ensure the particular service remains bonded for their individual service
It would seem to be an improvement to ensure that each flat has its own means of ensuring main bonding is reliably bonded by doing so locally to each flat

Bonding at the Gas meter in the garden would extend the zone outside of the building,I think it needs fitting where the pipe enters the building

If you consider the information in the guidance note on earthing and bonding then it makes it pretty hard to interpret the regs as only requiring bonding at the incoming.

 

[davesparks]

The main bonding would only need to installed within the gas floor boxes outside on the consumer side of the stop cock. The main water assuming this would be in the riser position would require a main bond only in the incomer position both sized in accordance to the main neutral. They won't require any additional bonding within the flat themselves as there are no other earth potentials being introduced. The submains to the flats will require a disconnection time of 5 seconds so no rcd will be required. Each flat would need rcds / rcbos internally split across lighting circuits etc as not to cause full failure if a fault occurs.
Normally if an underground extraneous pipe goes from one building to another both bonds would be required as to equalise both potential differences between them, I hope this helps.

Main bonding is required at the point of entry to an installation, gas meters are not necessarily the point of entry, especially if the meter is at ground level and the pipes enter the building at the first floor and above.

Each flat has its own electrical installation and therefore requires main bonding to each extraneous part. The fact that some service pipes are bonded at the incomes makes them extraneous to the flat's installation.
Each flat may also have additional extraneous parts of hot water, heating, air handling etc are centrally supplied rather than in each individual flat.

 

[Des 56]

If you consider the information in the guidance note on earthing and bonding then it makes it pretty hard to interpret the regs as only requiring bonding at the incoming.

I can't disagree with you and don't want to do so,my own comment on the bonding was made with the "definitive" advice given by Mikelukers post in mind

I said (it may be the case that the regs can be interpreted to require main bonding only at the point of entry)it was to make the point that even if it was to be bonded at the entry to the building,bonding at the flats would improve that decision

 

[Mikeluker]

if the main bond is in place though outside, and the submain carried its own earth connected to the main terminal this would also common up all of the bonding, nowadays assuming plastic incomers it would only be supplementary bonding and may not even be extraneous, the electrician on site would have to make this decision.

 

[davesparks]

if the main bond is in place though outside, and the submain carried its own earth connected to the main terminal this would also common up all of the bonding, nowadays assuming plastic incomers it would only be supplementary bonding and may not even be extraneous, the electrician on site would have to make this decision.

It's sim not just a case of communing up all of the bonding, each installation needs bonding installed to create an equipotential zone for the installation.
In this respect a block of flats is no different to a row of houses in a street, the physical distribution of the installations is vertical rather than horizontal but electrically they are same each with their own installation

 

[Mikeluker]

The position of the main protective bonding conductor to the services where they are considered an extraneous conductive part should be in accordance with BS7671 regulation 544.1.2.
The size of the main protective bonding conductor should be in accordance with BS7671 regulation 544.1.1 and where PME conditions apply Table 54.8.
The main protective bonding conductor should be connected to the main earth terminal in accordance with BS7671 regulation 411.3.1.2. This would normally be the earth facility provided by the supply/meter operator.
In a block of flats this position may vary depending on the position of the main earth terminal and the supply arrangements to each flat.
It is permissible to provide a "continuous" main protective bonding conductor to multiple services.