Gas pipe bond (IET vs Corgi)

[JohnW2]

You are confusing the two separate definitions of special location. One is the Building Regulation, which used to include kitchens for notifiable work and did not relate to the presence of water. The other is that of chapter 7 of BS7671 which relates to the presence of water and does not include kitchens.

I'm certainly confused, but not in the way you are suggesting.

What I wrote was nothing to do with the Building Regs or notification. I was talking about the requirements of BS7671 in relation to supplementary bonding. Am I perhaps wrong in thinking that BS7671 once required supplementary bonding in kitchens?

Kind Regards, John

 

[JohnW2]

<lots of things with which I agree>

For once, I managed to type faster than you

Kind Regards, John

 

[JohnW2]

If/when I have a few spare moments, I'll try a few more experiments!

One quick experiment done ...

....1 metre length of vertical plastic pipe, ID=16mm, filled with ('captive' and static, not flowing) Buckinghamshire very hard tap water. Resistance from end to end of the water was 40kΩ at both 250V and 500V (resolution of meter too low at 1000V). That means, if a full 230V were across a 1m length of such water-filled pipe, the current would be about 5.75 mA, proportionately less as the length of the pipe increased.

Kind Regards, John

 

[EFLImpudence]

What I wrote was nothing to do with the Building Regs or notification. I was talking about the requirements of BS7671 in relation to supplementary bonding. Am I perhaps wrong in thinking that BS7671 once required supplementary bonding in kitchens?

You may not be wrong in that the 15th edition required bonding to almost everything that was metal.

The thinking behind this is incomprehensible now and as it is no longer the case, presumably not related to water but just wrong.

 

[JohnW2]

You may not be wrong in that the 15th edition required bonding to almost everything that was metal.

That was, indeed, what I was thinking of (although I wasn't sure whether it was 15th or 16th ed.), but I thought that it only related to bathrooms and kitchens. Was it even wider in its scope than that?

Kind Regards, John

 

[Malc]

In terms of electrical common sense, that's obviously fine. You might also just about be able to argue that it is reg-compliant - the regulation says that "Where practicable, the connection shall be made .... at the point of entry to the building if the meter is external". Crucially, it does not say whether that 'point of entry' is the external or internal end of the hole through the wall, so you could certainly argue that you were compliant by bonding outside, close to where the pipe entered the wall!

That's my thought and assuming I put in the second connection in the floor void then if later someone says you can't have an external connection I would still have the one which could be inspected by cutting a hole in the floor under the bath. Although, strictly speaking the incoming pipe has to be connected within 600mm of entry into the house, it doesn't say that is 600mm inside so it could be 600mm outside .

'Bond' to what? If your concern is about the regulations, don't forget that it is very probable that there will not be a requirement for any supplementary bonding in the bathroom.
Even if there were a requirement for supplementary bonding (unlikley), it would only apply to "extraneous-conductive parts" (not to 'all pipewok' or 'all metal'), and if that pipework could be shown (by testing) to be effectively connected (via pipework and boiler etc.) to the installation's earthing system, then it would not count as an extraneous-c-p and therefore would not require siupplementary bonding.
I personally wouldn't bother with any of that, and I'm not even sure that it would satisfy the worst of "Jobsworths" - they might argue that the connection between clamp and pipe needed to be 'inspectable' (for corrosion, if not 'loosening'!).
I think that they sort-of do. I believe that DNOs use 'sprung' (rather than 'screwed') clamps onto their cable sheaths for TN-S earths. However, I'm not sure how available they are, and have never heard of one being used for a bonding connection!

Kind Regards, John

My concern is that the regs say all extraneous-conductive parts within the location are effectively connected to the MET. But maybe I am being too literal in interpreting extraneous as outside of the bathroom when what is meant is outside of the house? Because I'm taking it as outside the bathroom I'm concerned that a "Jobsworths" would see the metal radiator pipe disappear and so want that radiator to show connection to MET.

But in any case I'm now thinking the easiest solution is what you favour, isolating the radiator. That is measurable and also inspectable if the change to plastic is just under the floor, as then you could easily view it with a fibre-optic camera it you really wanted to. I reckon inspectable isolation is easier than having an inspectable bond joint where you'd want to give it a tug.

 

[JohnW2]

My concern is that the regs say all extraneous-conductive parts within the location are effectively connected to the MET. But maybe I am being too literal in interpreting extraneous as outside of the bathroom when what is meant is outside of the house?

I agree that there is a lack of clarity, which leads to some confusion. The definition of an "extraneous-c-p" is something that "is liable to introduce a potential, usually earth potential". Although it doesn't say so explicitly, what it obvioulsy means is "a potential which is (or may be/become) different from that of the MET" - that's why main bonding connects the MET to any extraneopus-c-p, to minimise any possible potential difference between them. If one accepts that, then if something can be shown to be effectively connected to the MET, it does not constitute an extraneous-c-p, since it cannot possibly be 'liable to introduce a potential' which is different from the potential of the MET.

But in any case I'm now thinking the easiest solution is what you favour, isolating the radiator.

It was EFLI, not me, who mentioned that, but I doubt that he would 'favour', let alone recommend/advise that anyone should do that. In my opinion, it would be way OTT to do that. Indeed, if you decided to do that, where would you stop? Would you similarly isolate the taps, the shower and anything else you could think of? If the radiator were already essentially isolated by virtue of plastic pipework, then fair enough (and I suppose that would be the 'ideal'). However, to actually expend time, effort and money to isolate an existing radiator (or taps, or whatever) is, in my opinion, really unnecessary - and I can't believe that many people would even consdier doing it.

Kind Regards, John

 

[EFLImpudence]

I don't want to read it all again, but -

wasn't it said that the radiators already had plastic pipe and only the visible bits were metal?

 

[JohnW2]

I don't want to read it all again, but - wasn't it said that the radiators already had plastic pipe and only the visible bits were metal?

I have a vague recollection that you may be right (and I don't want re-read it all again, either!) - but Malc's recent statement that he was now thinking that "the easiest solution [would be] isolating the radiator" seems to imply that this is something that he is now proposing to do. I'm sure that he will be able to clarify.

Do I take it that you agree with me that if the radiator is not currently 'isolated' that it would be OTT to expend effort to introduce such isolation?

Kind Regards, John

 

[EFLImpudence]

Perhaps he could measure the resistance from radiator pipes to MET and maybe save himself some work and pondering.

 

[JohnW2]

Perhaps he could measure the resistance from radiator pipes to MET and maybe save himself some work and pondering.

Indeed. As you are aware, I've recently indicated to him that anything which can be demonstrated to be 'effectively connected to the MET' (hence not an extraneous-c-p) does not need to be bonded, even if the requirements for omission of supplementary bonding were not satisfied (which I doubt).

Kind Regards, John

 

[EFLImpudence]

My concern is that the regs say all extraneous-conductive parts within the location are effectively connected to the MET.

I think that phrase effectively connected to the MET is only used regarding the omission of supplementary bonding when RCDs are protecting the circuits of the bathroom.

But maybe I am being too literal in interpreting extraneous as outside of the bathroom

No that is correct for supplementary bonding.

when what is meant is outside of the house?

That is not what is meant for supplementary bonding.

Because I'm taking it as outside the bathroom I'm concerned that a "Jobsworths" would see the metal radiator pipe disappear and so want that radiator to show connection to MET.

Then that jobsworth would be wrong in such a basic observation.
They may not require bonding.
They may be bonded elsewhere.
They may be otherwise connected.

But in any case I'm now thinking the easiest solution is what you favour, isolating the radiator. That is measurable and also inspectable if the change to plastic is just under the floor, as then you could easily view it with a fibre-optic camera it you really wanted to. I reckon inspectable isolation is easier than having an inspectable bond joint where you'd want to give it a tug.

Measurable is the operative word. Have you done any?

Supplementary bonding cannot be deemed correct or incorrect by looking at anything.

 

[stillp]

maybe I am being too literal in interpreting extraneous as outside of the bathroom when what is meant is outside of the house

The definition in IEC is "not forming part of the electrical installation".

 

[EFLImpudence]

But maybe I am being too literal in interpreting extraneous as outside of the bathroom when what is meant is outside of the house?

To clarify:

As far as supplementary bonding is concerned, it does just mean outside the bathroom.

However, just because a metal pipe comes from outside the bathroom does not mean it IS an extraneous-conductive-part.


The same applies, regarding main bonding from outside the building.

Extraneous-conductive-part is not a description of something judged by what it looks like; instead it is based on what it might do electrically.

 

[JohnW2]

To clarify: As far as supplementary bonding is concerned, it does just mean outside the bathroom. However, just because a metal pipe comes from outside the bathroom does not mean it IS an extraneous-conductive-part.

Indeed - and, as I said, although the definition in the regs does not say this explicitly, it's pretty clear that it means (or should mean!) that a conductor is only an extraneous-c-p if it is "liable to introduce a potential" different from that of the MET. In turn, that means that if it can be shown to be 'effectively connected' (i.e. with adequately low impedance) to the MET, is is not an extraneous-c-p.

Kind Regards, John