Flats with 10mm twin and earth

[dokkan1080]

Seen loads of flats are fed from a 60amp isolator in 10mm twin and earth?

don't they need to be 16mm tails and at least a 10mm earth?

or is it just down to the adiabatic?

 

[James]

What does the cable rating say for the installation method?

 

[Dave OCD]

Are you certain that the sub mains you've seen aren't 16mm rather than 10mm ? They do look quite similar but 16mm would be far more common.

 

[dokkan1080]

Are you certain that the sub mains you've seen aren't 16mm rather than 10mm ? They do look quite similar but 16mm would be far more common

Are you certain that the sub mains you've seen aren't 16mm rather than 10mm ? They do look quite similar but 16mm would be far more common.

My bad i meant 16mm twin and earth but still the earth is only 6mm?

 

[dokkan1080]

Its the same in my flat 16 mm twin 6mm earth

The bonding conductors are bigger than the 6mm earth

 

[Dave OCD]

Ah ok, it depends on what the bonding requirements are, and the earthing arrangement. If, for example the incoming water was plastic and there was no gas supply then the 6mm CPC would be perfectly adequate.

 

[dokkan1080]

Ah ok, it depends on what the bonding requirements are, and the earthing arrangement. If, for example the incoming water was plastic and there was no gas supply then the 6mm CPC would be perfectly adequate.

The gas and water are both 6mm but some one has also run 10mm to them no idea when that was.

Main earth is 6mm from the 16mm twin.

If I wanted the board changed would I need to have a 16mm earth run?

A new earth could be run easy straight out the wall and down to where the main intake is in conduit or something.

 

[dokkan1080]

Its the same in my flat 16 mm twin 6mm earth

The bonding conductors are bigger than the 6mm earth

If method A 61 amps?

 

[dokkan1080]

What does the cable rating say for the installation method?

earth

If method A 61 amps?

 

[Dave OCD]

If the supply is TNCS then yes you'd have to run an additional 10 or 16mm earth with a CU upgrade -assuming of course that the water and gas pipework is extraneous and actually needs bonding ? Whoever upgraded the bonding without paying attention to the main earth didn't really have a grasp of the requirements IMO.

 

[dokkan1080]

If the supply is TNCS then yes you'd have to run an additional 10 or 16mm earth with a CU upgrade -assuming of course that the water and gas pipework is extraneous and actually needs bonding ? Whoever upgraded the bonding without paying attention to the main earth didn't really have a grasp of the requirements IMO.

Not sure if its tncs but its to cold to go have a look...0.0

So if I get a 16mm main earth in leaving the new 10mm bonding and the old 6mm bonding on the gas and water would be okay?

Would the old 6mm earth from the twin and earth thats acting as the main earth from the met to the cu need to be disconnected or could it just be left in as well?

 

[Dave OCD]

You could just run a 10mm and leave the sub main cpc connected , the bonding appears OTT but that's fine too.

 

[dokkan1080]

You could just run a 10mm and leave the sub main cpc connected , the bonding appears OTT but that's fine too.

Ah gotcha :3

So leave all the bonding connected 10mm and 6mm

Leave the current 6mm earthing conductor connected and the new proposed 16mm or a 10mm earthing conductor connected as well.

My only thinking is if its in even if its over the top I won't have to worry about having to put new cables in at some time later on ?

 

[cliffed]

We’ve actually added 16mm earth cable to the T&E ,on flats we’ve tested.
The 10mm & earth is ok for a Distribution circuit,it’s a composite cable so the earth’s always smaller,worked out by calculation
The bonding should be appropriate to the supply 10mm if TNCS, so in this case back to the MET wherever that maybe.

 

[dokkan1080]

We’ve actually added 16mm earth cable to the T&E ,on flats we’ve tested.
The 10mm & earth is ok for a Distribution circuit,it’s a composite cable so the earth’s always smaller,worked out by calculation
The bonding should be appropriate to the supply 10mm if TNCS, so in this case back to the MET wherever that maybe.

What would be different if it was tns?

So if a 16mm earth is added from the met to cu you can run the 10mm bonding back to the cu earth bar as opposed to the met

 

[Darkwood]

There is always a lot of confusion on this subject and many do get it wrong...

Say you have an HMO with one common supply into the building that all the flats are then taken from, this common supply is where you would do you Gas and Water equipotential bonding if needed in the appropriate size bonding cable.
Running sub-mains to the flats in say 16mm T&E would not require you to add additional earthing, it is a circuit and only need to have a earth that meets its own requirements, the point of bonding Gas and Water is to ensure the pipes do not bring in a different potential earth than that of the electrical earth and nothing more, it is not about earthing the internal pipe network.

If the flats however are supplied individually with their own cutout and meter then yes there may be a requirement to bond the gas and water as it enters each flat if required.

This set up applies equally to all sectioned buildings like factories where the gas and water is shared through different units, if they all have independent supplies then they need independently to be bonded if required, however if they are all sub mains off the same common supply then no they do not as any bonding requirements would be done at source with the incoming supply, if the units have independent water and gas in metal then that could warrants each unit to be bonded separately and can either be done to the local submains earthing size permitting or run individually back to the incoming supply MET.

 

[cliffed]

What would be different if it was tns?

So if a 16mm earth is added from the met to cu you can run the 10mm bonding back to the cu earth bar as opposed to the met

Yes it’s then the correct main earth for that cable.
Usually the 16.00mm is a sub main cable not anticipating any main bonding conductors connections.

 

[dokkan1080]

Yes it’s then the correct main earth for that cable.
Usually the 16.00mm is a sub main cable not anticipating any main bonding conductors connections.

16mm is not anticipating any main bonding conductors?

 

[dokkan1080]

There is always a lot of confusion on this subject and many do get it wrong...

Say you have an HMO with one common supply into the building that all the flats are then taken from, this common supply is where you would do you Gas and Water equipotential bonding if needed in the appropriate size bonding cable.
Running sub-mains to the flats in say 16mm T&E would not require you to add additional earthing, it is a circuit and only need to have a earth that meets its own requirements, the point of bonding Gas and Water is to ensure the pipes do not bring in a different potential earth than that of the electrical earth and nothing more, it is not about earthing the internal pipe network.

If the flats however are supplied individually with their own cutout and meter then yes there may be a requirement to bond the gas and water as it enters each flat if required.

This set up applies equally to all sectioned buildings like factories where the gas and water is shared through different units, if they all have independent supplies then they need independently to be bonded if required, however if they are all sub mains off the same common supply then no they do not as any bonding requirements would be done at source with the incoming supply, if the units have independent water and gas in metal then that warrants each unit to be bonded separately and can either be done to the local submains earthing size permitting or run individually back to the incoming supply MET.

So would both of the following be acceptable?

Or would the gas bond need to be by the meter or as the pipe enters a flat

 

[Darkwood]

Firstly your crap at art ?..

Let's start with ensuring we are clear on what we are discussing, we are discussing Equipotential Bonding here, this should not be confused with earthing requirements of supplementary bonding which the pipework may fall into, so the following info and questions only relate to equipotential bonding.

The drawing lacks a lot of info'

Is this a HMO with one common power source for all the flats?
Is there one common Gas feed to the building?
Is there one common water feed to the building?

What you have to remember here is we bond gas and water at source so it does not bring a different potential in from natural ground to that of the electrical earth, this thinking has to be applied to such setups if say the gas and/or water is one source but is buried again in conductive pipe before reaching the flats, the guidance cannot give every scenario but understanding why we do equipotential bonding goes a long way to knowing when it is needed.

The problem we have in this industry is if you are a member of a scheme then the advice you get may differ depending on the scheme you are a member of and this only fuels the confusion, some schemes simply don't want to get into reviewing every scenario so they play it safe and say you should bond it, if this is the advice of your scheme then you should follow it as it is there approval you need when they inspect your work, if the gas and water is deemed it needs bonding in each flat then an additional 10mm bond would be required as the sub-supply earthing is simply too small, you can take this to the flat consumer unit and then bond from there or run a direct bond to the met.

What you need to do regarding earthing of gas and water pipes in flats if they do not need equipotential bonding is establish if they are conductive parts that require supplementary bonding and if so then earth them in accordance with the guidance.

If you are still confused I suggest you purchase a copy of the guidance notes 8 which goes deeper with pictorial examples.