O.S.G.

[EFLImpudence]

Looking for something else mentioned about the O.S.G., I came across this -

411.3.1.2 Metallic pipes entering the building and having an insulating section;
..............- of no less than 100 mm in length, and
..............- within 300 mm of the point of entry
..............need not be connected to the protective equipotential bonding.

As the length of the insulating section has no effect on the entering pipe, I presume they are referring to (possibly wrongly) bonding the consumer's side pipework, in which case, the length of the entering pipe is irrelevant.

Anyway - 411.3.1.2 does not state that - so who is it that just makes up this stuff and decides that whether a part is an extraneous-conductive-part or not is dependent on length?

 

[JohnW2]

Looking for something else mentioned about the O.S.G., I came across this -
411.3.1.2 Metallic pipes entering the building and having an insulating section;
..............- of no less than 100 mm in length, and
..............- within 300 mm of the point of entry
..............need not be connected to the protective equipotential bonding.
As the length of the insulating section has no effect on the entering pipe, I presume they are referring to (possibly wrongly) bonding the consumer's side pipework, in which case, the length of the entering pipe is irrelevant.

How bizarre - I've never noticed that one!

Anyway - 411.3.1.2 does not state that - so who is it that just makes up this stuff and decides that whether a part is an extraneous-conductive-part or not is dependent on length?

Quite so - and I suppose the answer is that the 'who' making this up is the IET (or, at least someone who has the IET's blessing).

Kind Regards, John

 

[conny]

The 300mm is to discourage someone branching off, (that's as effective as writing a label saying don't branch off here).
Why 100mm insulated section I have no idea. If it's a water pipe which is copper up to the exterior, then someone puts a small section of plastic through the wall and then does the internal piping back in copper, then the insulating section is pointless, surely?

 

[EFLImpudence]

The 300mm is to discourage someone branching off, (that's as effective as writing a label saying don't branch off here).

No it isn't.

Why 100mm insulated section I have no idea.

I presume it is to ensure that it insulates effectively. It is not mentioned anywhere else as far as I know.
However, the point is, it is irrelevant as far as bonding the incoming (entering) pipe.

If it's a water pipe which is copper up to the exterior, then someone puts a small section of plastic through the wall and then does the internal piping back in copper, then the insulating section is pointless, surely?

On the contrary. That would be far better than messing around with bonding.
It would ensure that the internal pipework would not require bonding.

 

[JohnW2]

The 300mm is to discourage someone branching off, (that's as effective as writing a label saying don't branch off here).

Maybe, but it's in contradiction with the actual regulations, which say that an incoming metal pipe shoulkd be bonded 'as close as practicable' to the point of entry. The OSG seems to be saying that one can forget that if there is 300mm or less of touchable extraneous-c-p within the property. That may correspond with common sense, but it is not what the regs say/require.

Why 100mm insulated section I have no idea.

I can understand that bit rather more. I suspect that they are merely defining the minimum length of insulating material that they would regard as representing a functionally-acceptable 'insulation section' - i.e. they would not accept a 20mm length of plastic (or a plastic plumbing fitting) as being adequate for an 'insulating section'.

If it's a water pipe which is copper up to the exterior, then someone puts a small section of plastic through the wall and then does the internal piping back in copper, then the insulating section is pointless, surely?

Eh? In the situation you described, there would be a very good 'point', since it would mean that there was no extraneous-c-p within the building - hence no bonding required.

Kind Regards, John
Edit: too slow again!

 

[conny]

Points taken.