Bonding question.

[La Poste]

Hello guys I am going to show my ignorance now so please don't shoot me down in flames.

I have a guy who wants an extension to a circuit, he wants light and power to his garden shed.

He has an TN-S supply with an amazing 0.18 Ohms ELI.

16mm main earth conductor and old Wylex BS3871 MCB's.

He has had extensive work done to his house including many electrical installations, central heating, kitchen down lights etc.

The CU is in a cupboard under the stairs and has a solid concrete floor, many extensions have been added to his house.

After having all this work done I was disappointed to see he has no main bonding conductor to his water intake.
It has been completely neglected.

I have measured an R2 reading of less than 0.05 Ohms from the main water intake to the CU but I am guessing this is coming from the small CPC of the boiler supply cable and also the gas pipe bond (yes the gas pipe has been bonded) the boiler has also been cross bonded with the water pipes inside.

Now seeing as how this main bonding cable is so impossible to fit I was wondering if there was any way round it.

Is it possible to bond from the main water intake to the boiler which is a short run and then cross bond so that the gas pipe supplies the necessary low resistance path back to the consumer unit?

Basically using the gas supply pipe as a substitute to the main water bonding conductor.

I noticed another extension elsewhere in the house with a sink and someone has put a bonding clamp on the sink water supply pipe and connected a 6mm cable to it, I can only assume this 6mm cable is then terminated in a socket near to the sink as this bonding cable sure does not arrive at the consumer unit by itself, the socket that this bonding cable is connected to is a ring circuit back to the CU.

Using a gas pipe as a substitute to a main bond send shivers down my spine but I was interested to know what peoples thought are on this.

How flexible can we be with Bonding, does it have to be a cable that supplies the bond or can we use other means?

In an ideal world I would be able to run a 10mm bonding conductor from the main water intake back to the MET but this is not an ideal world.

Any opinions welcome.

Many thanks.

 

[DurhamSparky]

Simple answer NO

can you not attach to water pipe at a more easier location???

 

[La Poste]

It doesn't look like it.

At the moment the best way seems to run the bonding cable up the outside of the house, drill through the wall, lift upstairs floor boards, run the cable through a bedroom and the hall and then drop the cable down through the ceiling of the little concrete bunker that the CU is housed in.

The trouble is when I try explaining this to the client he looks at me funny, well his wife looks at me funny like I am making it all up and just trying to invent work for myself.

People just do not understand what is involved and the regulations that govern us.

 

[Octopus]

Without wishing to teach you to suck eggs but there is a very useful leaflet on the ESC website covering this - I've often sent a copy or provided a weblink for a customer who wants to see more info.

 

[Robinson]

Without wishing to teach you to suck eggs but there is a very useful leaflet on the ESC website covering this - I've often sent a copy or provided a weblink for a customer who wants to see more info.

That is a very sensible approach to dealing with customers lack of understanding. And really its fair enough on their part why would they have a clue about necessary earth bonding arrangements. Least this way they see ya not pulling the proverbial wool.

 

[topquark]

A plumbing solution would be to install a run of plastic pipe just after the stopcock

 

[La Poste]

A plumbing solution would be to install a run of plastic pipe just after the stopcock

Hey I like the sound of that. :yesnod:

 

[Engineer54]

If the main gas pipe bonding point is in the same vicinity as the main water pipe bonding point, then you may connect the water main with the same bonding conductor that is connected to the gas main point... .

 

[telectrix]

however, BS7671 is not statgutory. if you can show that the bonding to the water is a safe as if it was done to BS7671, then it could be recorded as a departure. tin hat time .

 

[DurhamSparky]

bing !! bing!! woosh BANG!!!

 

[La Poste]

Funny thing is the main gas bond is attached to the outgoing side of the gas meter which is about 1 metre from where the supply cable enters the building IE inside the little concrete bunker, they are right next to each other.

The main water intake on the other hand is the other side of the house, about 10 metres away.

 

[telectrix]

that is so inconsiderate of the gas and water suppliers, to bring their supplies in at the opposite sides of a house. but then again, their contractors are plumbers and gas fitters that can't hack it in the real world so what do you expect?

 

[Richard Burns]

Normally the easiest thing to do is run the bonding straight out round the outside the house, possibly under rain deflectors, if any, so it is less visible and back in where the CU is located. But not knowing the house layout it is difficult to advise correctly. Using the gas pipe does not seem a good move in case things are changed around and does not meet the regs, unless you use Tels solution!

 

[La Poste]

I was wondering maybe cables in parallel, I have two individual ring mains close to the water pipe giving me 6mm of earth cable (4 times 1.5mm), and it's a TN-S system, minimum bonding conductor size could be 6mm.

I have to look at the adiabatic I2T but I think 6mm will be OK.

It might be a solution, using ring main circuit CPC as a main water Bonding conductor, what do you think?

Thanks.

 

[Deleted member 26818]

The adiabatic works out to about 3.8mm² with an MCB, so 6mm² should be fine.