Main bonding to water question

[tomlonsborough]

Hi folks,

Just wanted to check and see if bonding is required in this situation:

• There's no bond to water pipework, bond to gas all present and correct
• There is a piece of plastic pipe at the point where the water enters the building, probably around 100mm in length
• There is then a mix of copper and plastic water pipework throughout the installation
• I don't think there's any metal water pipework which penetrates the floor at any point after the service comes into the building
• There is no continuity between any of the copper water pipework and the MET (Megger reads >99.9kOhm)

I'm erring on the side of not required, however if anyone could shed any light otherwise I'd be very grateful!

Tom

 

[Loki]

From what i understand the Niceic uses 230/0.03 = 7667 ohms

Any figure over this 7667 Ohms doesn't require bonding.

 

[Midwest]

Think you need to set your a Megger to a different test, the >99.9k.

Have a shuffty at this vid. Otherwise I’d agree with you;

View: https://www.youtube.com/watch?v=v38PfIVy2rI

 

[JBW175]

Metallic pipes entering the building having an insulating section at their point of entry need not be connected to the protective equipotential bonding.

The 100mm of plastic pipe you have on entering the building is classed as insulating material, so therefore, there is no requirement for bonding.

 

[Pete999]

From what i understand the Niceic uses 230/0.03 = 7667 ohms

Any figure over this 7667 Ohms doesn't require bonding.

That figure is for "Protective Supplementary bonding" not main equipotential bonding!

 

[Loki]

Think you need to set your a Megger to a different test, the >99.9k.

Have a shuffty at this vid. Otherwise I’d agree with you;

View: https://www.youtube.com/watch?v=v38PfIVy2rI

In this video he says at 2mins in that under 1667 ohms doesn’t need bonding & over 1667 ohms it does. Is that correct? Thought it was the other way round?

 

[tomlonsborough]

In this video he says at 2mins in that under 1667 ohms doesn’t need bonding & over 1667 ohms it does. Is that correct? Thought it was the other way round?

As I understand it, a resistance between extraneous/exposed of 0-1667 Ohms will be fine on RCD protected circuits, and a resistance of >22000 Ohms will be fine because they are sufficiently isolated from one another. The "dangerzone" is between 1667-22000 Ohms where bonding would be required. On an MFT you would use the low resistance Ohm meter function to measure the 0-1667 range, otherwise you would need to use the IR functionality to measure the 22k+ range.

Does that sound about right?

 

[richy3333]

Isn't this now written in the Regs as people seem so confused about it, else cant do the test

 

[Pete999]

Isn't this now written in the Regs as people seem so confused about it, else cant do the test

I think Guidance Note 3 us the document to look at!!

 

[Midwest]

Which bit, R< 50 V/Ia?

 

[Pete999]

Which bit, R< 50 V/Ia?

Yep, don't have a copy personally Mate

 

[Midwest]

Mines in the loft! Reg 415.2.2. Didn't that nice bloke John Ward, do a vid on it Pete?

 

[Pete999]

Mines in the loft! Reg 415.2.2. Didn't that nice bloke John Ward, do a vid on it Pete?

Like you Mate I'm retired, and have passed all my books on to someone who will make use of them, yes JW an d Chris Kircher did vid on the subject Chris's vid on Main bonding is very informative.

 

[Midwest]

Like you Mate I'm retired, and have passed all my books on to someone who will make use of them, yes JW an d Chris Kircher did vid on the subject Chris's vid on Main bonding is very informative.

Here you go;

View: https://www.youtube.com/watch?v=CVxBettQpPU


Bloody nice bloke is that JW.

 

[Wilko]

There is a piece of plastic pipe at the point where the water enters the building, probably around 100mm in length

Hi - Reg 411.3.1.2 now has a statement regarding this, my take is that it makes connection optional where an insulating pipe section has been used. You don’t have to do it, but if it’s there you don’t have to remove it. I’d note on your certificate what you’ve observed.

 

[HappyHippyDad]

As I understand it, a resistance between extraneous/exposed of 0-1667 Ohms will be fine on RCD protected circuits, and a resistance of >22000 Ohms will be fine because they are sufficiently isolated from one another. The "dangerzone" is between 1667-22000 Ohms where bonding would be required. On an MFT you would use the low resistance Ohm meter function to measure the 0-1667 range, otherwise you would need to use the IR functionality to measure the 22k+ range.

Does that sound about right?

I've never quite understood how we can accept the <1667ohms bit. I understand the maths, in that the RCD will trip within given times if L-E <1667 ohms. However, we use 200 ohms for a rod as this is deemed stable. How can we accept say 1666 ohms when testing for extraneous as this could easily pop over that figure in dry weather.

 

[Pretty Mouth]

I've never quite understood how we can accept the <1667ohms bit. I understand the maths, in that the RCD will trip within given times if L-E <1667 ohms. However, we use 200 ohms for a rod as this is deemed stable. How can we accept say 1666 ohms when testing for extraneous as this could easily pop over that figure in dry weather.

Do you mean testing to see if supplementary bonding is required? If R <= 50/Ia between exposed/extraneous parts, then no need for sup bonding? If so, then the exposed/extraneous parts are already connected to the MET, either bonded or earthed, and so there should only ever be a few ohms between them.

You'd never get close to a fraction of 1667ohms, and if you did then you've probably identified an extraneous that hasn't been main bonded.