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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almost certainly need RCD protection, again this is something which changed in 2008 so there is no excuse for being out of date with the regulations.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 .
 
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
 
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.
 
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.
 
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!!!
 
Last edited:
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
 
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
 
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.
 
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.
 
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
 
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.
 
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
 
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.

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