bonding question

[D Skelton]

Hi guys, I haven't got my BGB to hand, does anyone know if there is anything in the new amendment regarding bonding and specificly the need to do it when incoming services are plastic?

 

[malcolmsanford]

No as far as I'm aware there isn't a regulation that deals specifically with non metallic services. About the only mention you will get is reg 544.1.2 where in mentions an insert.

A good way of knowing if something is a regulation is in either the GN3 or OSG. The section in the OSG relating to. The OSG in section 4.3 which covers Main protective bonding guide you towards 411.3.1.2 but these tell you what needs bonding

Section 4.5 for plastic service only quotes 544.1.2 as I have above and no other section

 

[D Skelton]

So pretty much the same as the old BRB then. Cheers Malc

 

[Tonkatoy27]

I don't think you should be worried about what the incoming supply pipe material is, what counts is the water pipes IN the property. If it's all copper from the buildings stop cock then it obviously needs bonding, if it's all plastic then not.

 

[malcolmsanford]

Why Tonkatoy does the metallic side of the installation need bonding? What if none of that metal work is an extraneous conductive part?

To carry your argument on then any metalwork within an installation must be bonded, because it is metal

 

[D Skelton]

I don't think you should be worried about what the incoming supply pipe material is, what counts is the water pipes IN the property. If it's all copper from the buildings stop cock then it obviously needs bonding, if it's all plastic then not.

The problem is Tonka, these days, the pipework in a lot of houses is a mish mash of both copper and plastic all over the shop. It only takes one unseen plasic compression joint to render your bonding in that situation completely useless anyway. Remember, bonding is there only to limit the value of touch voltages, it can't do this if the incoming services bonded have plastic incomers.

I'm aware of what it says in the BRB, I simply wanted to know if anything had changed.

 

[topquark]

Why Tonkatoy does the metallic side of the installation need bonding? What if none of that metal work is an extraneous conductive part?

To carry your argument on then any metalwork within an installation must be bonded, because it is metal

Exactly Malc. I'll be bonding all the saucepans in the kitchen and knives and forks in the draws on that basis (and the biscuit tin!).

 

[Tonkatoy27]

Agree wholehartedly with the fact that there is plastic and copper water installations everywhere now which makes a mockery of our bonding regulations.
Now I may of not got much sleep last night due to my nocturnal son but if I'm not mistaken then 411.3.1.2 says that protective equipotential bonding shall be applied to water pipes. (if metal of course) End of.
But to answer the original question, no, I'm not aware of anything in amd 1 changing what we've always had to do with a metal water service inside the property.

If I've got hold of the wrong end of the stick and you're all talking about something completly different to me then I better go for a lie down.

 

[Amp David]

Exactly Malc. I'll be bonding all the saucepans in the kitchen and knives and forks in the draws on that basis (and the biscuit tin!).

What about the spoons?

 

[malcolmsanford]

The keywords for reg 411.3.1.2 is the term Extraneous conductive parts mate.

Metallic water pipes are and plastic ones are not.

As you know we only carry out Protective equipotential bonding on ECPs as they are liable to introduce a potential into the installation as most pipework coming into a building is more or less somehow in contact with the earth, and so when metallic they are very likely to introduce this potential, when plastic they are not.

So if you have an incoming plastic water pipe coming into the building and it terminated into a stop cock, but then the secondary side of the installation is metal, is that metal an ECP, chances are not, as long as it is not picking up a potential from another source.

There is a chance that it might connect to a boiler that has a gas main that is metallic and therefore that secondary metal work can become an ECP. But this is why we can test the metal work by carrying out an IR test between the pipework and the MET and if it exceeds 22Kohm then it is not an ECP and not requiring bonding.

 

[Amp David]

The last rewire I did, there was no bond run in for the water, as at the time of first fix customer had planned on running all internal pipe in plastic. This changed when their plumber decided otherwise and ran the cold and hot domestic water all in copper.

Thought i'd check at the incoming stop tap to see if extraneous or not and surprise surprise it wasn't., as the water supply had been replaced with HDPE pipe.

This is the job I am planning to use for my next assessment so can't wait to see what they say.

End of the day its not extraneous so it doesn't need bonding, but because internal pipe work is copper, I bet they expect to see it bonded.

 

[Tonkatoy27]

Great explanation, very clear and concise. Thanks. I would think that you are applying this to new build where you know that everything else installed is perfect and up to your own high standards.
Now, I mostly do small works in existing properties. If I'm reading your post correctly, you would not insist on main earth bonding being present at a house with a plastic incoming pipework with an IR value to earth of over 22Kohm if you were say, changing the CU.
What if the dodgy chock block connection under the floor then melted against pipework?
Surely it's better to bond anyway?

 

[D Skelton]

Great explanation, very clear and concise. Thanks. I would think that you are applying this to new build where you know that everything else installed is perfect and up to your own high standards.
Now, I mostly do small works in existing properties. If I'm reading your post correctly, you would not insist on main earth bonding being present at a house with a plastic incoming pipework with an IR value to earth of over 22Kohm if you were say, changing the CU.
What if the dodgy chock block connection under the floor then melted against pipework?
Surely it's better to bond anyway?

What if dodgy choc block connection came loose against metal window frame?

 

[Tonkatoy27]

I know what you're saying and quite agree we can't protect against everything.
I don't think this lady would agree however.
Young mother electrocuted by live tap as she ran a bath in her family's new home | Mail Online

Yes I know it sounds like the lack of water bonding was the least of their troubles but if it was there it would of helped.

Water systems, by there very nature are going to be more dangerous than a window frame if something goes amiss. I don't think I'd be very happy if my family were living in a house without bonding to the water installation.

 

[malcolmsanford]

Read the article

enamel bath combined to turn the metal bath taps into a live electrical conductor.

that the home hadn't been rewired or inspected electrically since 1981.

The 35-year-old volt trip switch to the main fuse board was not working

heat the bath, was more than 30 years old, had a damaged flex and the wrong size fuse was fitted to the plug.

There is such a catalog of things here and for me it would seem to be a TT system when it said the Volt trip was not working, and of course bonding. But those taps were ECPs and introducing a potential, whereas if they were not ECPs then they wouldn't be.

Ok say this then, the taps were not ECPs and never needed bonding but you bond them because it is better to be safe than sorry.

You have your hand on this heaters chasis which is an exposed conductive part and therefore has a CPC and there is a fault on the unit like it was there and the fault was not cleared. So the Chassis becomes live carrying that fault and your touching it, and at the same time your touching the taps which you bonded and so also become an exposed conductive part because they have by you bonding them become a CPC , you now will have the fault voltage across your arms and going down you making earth. Chances are they could kill you.

But say you was touching the chassis and holding a metal tap that you just took out of a box and was free to air not in contact with earth, what do you think may happen