A bit of bondage!

[EFLImpudence]

...but without them, without quoting every regulation, the equation of 415.2.2 is a good test, although GN3 recommends 0.05Ω.

Agreed. The GN3 recommendation is a bit more demanding, but have you, in practice, found (m)any installations in which the 415.2.2 test is not satisfied?

No, but I only work in town, i.e. small properties. I don't work in large country houses where it may be different.
Gas fitters still insist I bond all the pipes entering a boiler.

Also if disconnection times cannot be met. A better term for this would be Supplementary Earthing, but that would be another kettle of worms.

Very true. This (and, indeed, the 'bath scenario') are examples of those situations in which, whether they like it or not, people simply have to accept that the concepts of bonding and earthing can get totally muddled up with one another.

Interconnected (obviously) rather than muddled.

In the 'floating bath scenario' it is not 'bonding' which creates a hazard, it's the earthing which comes with the bonding

Only IF you bond it which I am adamant you should/must not.

.... If so, in practice, it would seem that there is effectively never going to be a need for Supplementary Bonding, provided that there is MPB and RCD protection - is that how you see it?

Yes, but you say it as if it were a bad thing.

Not at all. I am again simply trying to ascertain whether you feel that, in practice, there is every going to be a need for Supplementary Bonding (given the presence of 'mandatory' MPB and the near certainty of an RCD - at least, in recently designed circuits).

If not, then so be it.

Are you surpised that I am agreeing with you?

Somewhat. I thought I was never going to get out of this one.

 

[JohnW2]

No, but I only work in town, i.e. small properties. I don't work in large country houses where it may be different.

Thanks. That's what I expected.

In the 'floating bath scenario' it is not 'bonding' which creates a hazard, it's the earthing which comes with the bonding

Only IF you bond it which I am adamant you should/must not.

That's what I meant - the point being that if you do bond, the 'bonding' (rendering the metal parts at either end of the bonding conductor equipotential) does not create any hazards - it's the unavoidable earthing which comes with the bonding (which you are adamant should not exist) which produces the hazard.

Are you surpised that I am agreeing with you?

Somewhat. I thought I was never going to get out of this one.

Ah well, the occasional surprise won't do you any harm

Kind Regards, John.

 

[david911cockburn]

What does 'loop impedance' control?

 

[holmslaw]

What does 'loop impedance' control?

Nuffink, hows your knob.

 

[sparkticus]

What does 'loop impedance' control?

Loop impedance controls nothing.

loop impedance limits conductance in the phase-phase/phase-N/phase-E fault path.

Another way of saying that: LI defines the maximum current that can flow in a given circuit under fault conditions.

In a fault, as the temperature rises the LI will increase. It is being controlled, it is not in control.

Hopefully the initial LI at ambient or conductor operating temperatures will be low enough to cause activation of the ADS within the specified time frame.

 

[david911cockburn]

Are you saying that 'loop impedance' controls speed of isolation?

 

[sparkticus]

Are you saying that 'loop impedance' controls speed of isolation?

I am saying that loop impedance is controlled by conductor temperature, conductor material, conductor CSA, conductor length, supply frequency and reactive components. Loop impedance is a factor of the mean free path afforded to electron flow by the environmental factors within a conductor.

 

[sparkticus]

Are you saying that 'loop impedance' controls speed of isolation?

I am also saying that loop impedance is a factor (a component) of determining speed of isolation. It is by no means the only factor. In the context of your question loop impedance as recorded during an electrical test at a given temperature is only an initial parameter. Loop impedance is dynamic and will rise under fault conditions.

What point are you making in asking the question?

 

[riveralt]

What does 'loop impedance' control?

I am also saying that loop impedance is a factor (a component) of determining speed of isolation. It is by no means the only factor. In the context of your question loop impedance as recorded during an electrical test at a given temperature is only an initial parameter. Loop impedance is dynamic and will rise under fault conditions.

What point are you making in asking the question?

He's research/writing another chapter in his ""best selling book/pamphlet"" - (how many pages constitutes a book).

Sparkticus - don't encourage him.......

 

[ricicle]

Gentlemen - do not feed the TROLL

 

[matt1e]

Gentlemen - do not feed the TROLL

Seconded

 

[sparkticus]

What does 'loop impedance' control?

I am also saying that loop impedance is a factor (a component) of determining speed of isolation. It is by no means the only factor. In the context of your question loop impedance as recorded during an electrical test at a given temperature is only an initial parameter. Loop impedance is dynamic and will rise under fault conditions.

What point are you making in asking the question?

He's research/writing another chapter in his ""best selling book/pamphlet"" - (how many pages constitutes a book).

Sparkticus - don't encourage him.......

I guess you are right. I certainly don't want to contribute to his sales brochure... sorry I meant his book

 

[david911cockburn]

OK, let's start with something a little easier for those of us who lack a little self confidence in the subject.

Can anybody see a relationship between nominal supply voltage (240v), perspective fault current and 'loop impedance'?

 

[stillp]

Does perspective fault current appear smaller if you stand further away?

 

[sparkticus]

OK, let's start with something a little easier for those of us who lack a little self confidence in the subject.

Can anybody see a relationship between nominal supply voltage (240v), perspective fault current and 'loop impedance'?

That depends upon your perspective