Bonding gas/water yellow and blue

[Houndogg10]

Hi I am recently qualified and still have a lot of learning/reading to do but Blue plastic waterpipe incoming, seems to always be a grey area with electricians I work with, me personally wouldn’t bond it..... Although we have to prove that in the plumbers install their is no copper going to earth?? Can someone enlighten me on this please

Many thanks..... and go easy on me lol

 

[Ian1981]

Agreed. But.... not relevant. If that was acceptable then you could say let’s only bond the gas even if the water is on a metallic supply pipe as it’s all at the same potential.

I’m only interpreting the regs.

no you couldn’t say that because the pipework could be altered or even disconnected which is why we provide bonding as close to the intake position as possible and before any branches or tee sections

 

[Midwest]

It’s not a test to verify supplementary bonding at all.
As bs 7671 states where doubt exists about the effectiveness of supplementary bonding conductors then the formula 50/Idelta N can be used in the case of an rcd or 50/Ia , if No rcd ,can be used to determine the effectiveness of the supplementary bonding to pipework

I don't how to respond to your post, isn't your first & second paragraph the same statement?

 

[Ian1981]

I’m saying testing a piece of metal to see if it’s an extraneous conductive part isn’t the same test to verify supplementary bonding conductors where doubt exists over there effectiveness.
I thought it was quite clear really.

 

[Midwest]

I’m saying testing a piece of metal to see if it’s an extraneous conductive part isn’t the same test to verify supplementary bonding conductors where doubt exists over there effectiveness.
I thought it was quite clear really.

I'm not trying to be confrontational, just trying to understand. I thought there was only one testing procedure, aka 415.2.2 and or Chris Kitcher video explanation.

 

[Ian1981]

I'm not trying to be confrontational, just trying to understand. I thought there was only one testing procedure, aka 415.2.2 and or Chris Kitcher video explanation.

No confrontation by me was meant it’s just the way the txt has come out I think.
I know the testing of extraneous parts comes from Gn8 and the 10mA “yeah I felt that “ approach.

 

[Midwest]

No confrontation by me was meant it’s just the way the txt has come out I think.
I know the testing of extraneous parts comes from Gn8 and the 10mA “yeah I felt that “ approach.

I'll have a read of GN8 & 3. Only asking as I come across a lot of existing PME installs, with existing bonding to plastic copper combo's in 6mm (16mm tails).

Edit; think I asked some advice from Elecsa Tech', see if I can dig up their response. I know the stance now with a metal service, is it must be upgraded to 10mm, whatever. Which is a nonsense, when doing some minor work!

 

[Deleted member 26818]

You don’t have to upgrade, unless there is evidence that the existing bonding is under stress.

 

[Ian1981]

I'll have a read of GN8 & 3. Only asking as I come across a lot of existing PME installs, with existing bonding to plastic copper combo's in 6mm (16mm tails).

Edit; think I asked some advice from Elecsa Tech', see if I can dig up their response. I know the stance now with a metal service, is it must be upgraded to 10mm, whatever. Which is a nonsense, when doing some minor work!

Well this is from the Electrical safety council website.
It’s down to the installer I guess and his interpretation of the requirements of bs 7671
Q1.67 When carrying out electrical work on an installation forming part of a TN-C-S system, is it necessary to upgrade existing 6 mm² protective equipotential bonding to 10 mm²?
Not necessarily. If the existing 6 mm² bonding connects all the extraneous-conductive-parts to the main earthing terminal, has been in place for a significant time and shows no signs of thermal damage, then it may not require to be upgraded.

Regulation number(s)

• 132.16
  
• 544.1.1

 

[Midwest]

There has been - Certsure wise - a change to that particular guidance. As its taken me about ten mins to post these few lines, I'll post tomorrow, when its less busy!

 

[Ian1981]

There has been - Certsure wise - a change to that particular guidance. As its taken me about ten mins to post these few lines, I'll post tomorrow, when its less busy!

Well I can’t see how say you move a light switch from one wall to another and you complete a minor works certificate PME earthing arrangement.
If the main protective bonding is in 6mm and has been there say all the installations life maybe 30 years, then to say you have to upgrade to 10mm which could be a pig of a job is ridiculous in my opinion

 

[Richard Burns]

Even with a plastic incoming water supply, if the installation is completely metallic (copper) it will almost definitely be introducing earth potential via the connection at the boiler. Where the plumber has bonded all the pipes together at the boiler as in the above picture, you can be sure all the metallic pipework will be introducing earth potential as the gas supply pipe to the boiler will be metallic and earthed at the boiler.

So unless you can confirm the pipework is not at earth potential (which it will be if it is an all metallic installation and the boiler supply is correctly earthed) then it will need bonding.

The external earth potential that is being introduced into the property will come from the gas supply pipe which is bonded at the point of entry, this covers the bonding requirements; otherwise you would need to bond the gas pipe every few centimetres because it is connected to another bit of metal just before it that is introducing earth potential and so on. The water pipes are not introducing a new earth potential they are just extending the area over which the already bonded service spreads.

Well I can’t see how say you move a light switch from one wall to another and you complete a minor works certificate PME earthing arrangement.
If the main protective bonding is in 6mm and has been there say all the installations life maybe 30 years, then to say you have to upgrade to 10mm which could be a pig of a job is ridiculous in my opinion

On a minor electrical installation works certificate you sign to say that the safety of the installation has not been impaired by your work.
This implies that there is no requirement to enhance the safety of the installation to the current regulations despite the requirement that earthing and bonding is adequate for the protective measure applied.

 

[Ian1981]

The external earth potential that is being introduced into the property will come from the gas supply pipe which is bonded at the point of entry, this covers the bonding requirements; otherwise you would need to bond the gas pipe every few centimetres because it is connected to another bit of metal just before it that is introducing earth potential and so on. The water pipes are not introducing a new earth potential they are just extending the area over which the already bonded service spreads.

On a minor electrical installation works certificate you sign to say that the safety of the installation has not been impaired by your work.
This implies that there is no requirement to enhance the safety of the installation to the current regulations despite the requirement that earthing and bonding is adequate for the protective measure applied.

I’m interested into what Midwest has previously said about that change to the existing guidance on it.
Tho I suspect upgrading the bonding is more to do with New works carried out.
I’m aware that there’s no statutory law that requires that an electrical installation needs upgrading to the current regulations if you like but that new work must be designed and installed to the current edition of bs 7671.

 

[Midwest]

I’m interested into what Midwest has previously said about that change to the existing guidance on it.
Tho I suspect upgrading the bonding is more to do with New works carried out.
I’m aware that there’s no statutory law that requires that an electrical installation needs upgrading to the current regulations if you like but that new work must be designed and installed to the current edition of bs 7671.

Page 39, first question;

Connections - Spring 2016 - https://issuu.com/redactive/docs/con_spr16_full_lr

This was a change from the previous guidance, quoting thermal damage etc.

Its somewhat vague, as to what constitutes 'new work', that is only implied in the question, not given in the answer.

But I agree with you Ian, in some circumstances it would be ridiculous. Upgrading the bonding, typically water, would be vastly more, than the cost of some new works.

 

[Midwest]

I’m saying testing a piece of metal to see if it’s an extraneous conductive part isn’t the same test to verify supplementary bonding conductors where doubt exists over there effectiveness.
I thought it was quite clear really.

I've been reading GN8 as you suggested, specifically 6.1 - definition of an extraneous-conductive-part. It suggests where a conductive part might be partially insulated from Earth via insulating material, it recommends the use of equation (not 415.2.2) Rcp>(Uo/IB) - ZTL

Now my maths is not good, so using its example, and the use of 10mA (let go threshold), reveals a figure of 22 kohms, so any conductive part above this figure, is not to be considered an extraneous-conductive-part. Conversely, anything under this figure is, and should be bonded.

Is that correct thinking?

 

[Ian1981]

I've been reading GN8 as you suggested, specifically 6.1 - definition of an extraneous-conductive-part. It suggests where a conductive part might be partially insulated from Earth via insulating material, it recommends the use of equation (not 415.2.2) Rcp>(Uo/IB) - ZTL

Now my maths is not good, so using its example, and the use of 10mA (let go threshold), reveals a figure of 22 kohms, so any conductive part above this figure, is not to be considered an extraneous-conductive-part. Conversely, anything under this figure is, and should be bonded.

Is that correct thinking?

Carrying out a 500 v IR test from the MET to the piece of metal if you get 0.02 Mohms or higher then it’s believed not to be extraneous that is it won’t induce an earth potential if you follow the formula 230/ 0.01 amps= 23000 ohms.