A bit of bondage!

[sparkticus]

What about the first two lines:

"Either by luck or by judgement, flexible cables that we use every day are something that is very difficult for the human hand to get a firm grip of"


What utter nonsense! With suspicious grammar.


Has anyone actually purchased this work of garbage?

 

[david911cockburn]

Hi All,

Alternative methods include, insulation, the use of barriers or placing out of reach.
Which do you suggest are used for radiators?

Over these last few months a debate has ben taking place in order to find out why you all believe you can get away without earthing, it has now come to light that the reason is that Chapter 41 of the 16th Edition was assumed to offer a number of loop impedance values that if achieved removed the need for supplementary equipotential bonding. But in reality this is not the case, Chapter 41 of the 16th Edition offers a number of loop impedance value that if cannot be achieved result in a need for the addition of 'local' supplementary bonding.

 

[Spark123]

It depends wether or not it is an extraneous conductive part.
If it is fed via plastic pipes such as it is sufficiently insulated from any other system then it is not extraneous hence better not to bond it at all.

Also please stop referring to the 16th edn, it is out of date. The current edition of the regs is the 17th edn BS7671:2008, in Jan it will be BS7671:2008 + Amd 1:2011.

edit, changed 2nd one to + Amd

 

[matt1e]

Hi All,

Alternative methods include, insulation, the use of barriers or placing out of reach.
Which do you suggest are used for radiators?

nothing if its not an extraneous conductive part

Over these last few months a debate has ben taking place in order to find out why you all believe you can get away without earthing, it has now come to light that the reason is that Chapter 41 of the 16th Edition was assumed to offer a number of loop impedance values that if achieved removed the need for supplementary equipotential bonding. But in reality this is not the case, Chapter 41 of the 16th Edition offers a number of loop impedance value that if cannot be achieved result in a need for the addition of 'local' supplementary bonding.

1) no one has mentioned getting away without earthing anything, you are still confusing "earthing" and "bonding"
2)Do you mean if the value is too low then it's deemed to be extraneous and so req bonding and as far as I am aware nobody is disputing that either
I think you need to read things more slowly, It might sink in

Matt

 

[matt1e]

ok A quick quiz
read the regulation then answer the question in the picture

Earthing or other suitable precautions
8. Precautions shall be taken, either by earthing or by other suitable means, to prevent danger arising when any conductor (other than a circuit conductor) which may reasonably foreseeably become charged as a result of either the use of a system, or a fault in a system,

Note the words in bold they are relevant

View media item 35703
I'll go first if you like
I can foresee three reasons to go for (b)

 

[sparkticus]

If it is fed via plastic pipes such as it is sufficiently insulated from any other system then it is not extraneous hence better not to bond it at all.

Exactly, otherwise we would need to "bond" metal toothbrush holders.

Also please stop referring to the 16th edn, it is out of date. The current edition of the regs is the 17th edn BS7671:2008, in Jan it will be BS7671:2011.

He thinks "our" lack of "his" understanding has its roots in the 16th.
He clearly has his roots in the 16th century.

 

[matt1e]

or possibly four

 

[sparkticus]

I'll help Mr Cockburn with one possibility:

Table lamp flex is worn exposing phase conductor (lucky it is difficult to grip by the human hand eh?)

Child grips it (against all odds)

Child simultaneously in contact with radiator.

Floating radiator: Result: small potential difference across "live" child.
Bonded radiator: Result: huge potential difference across "dead" child


What did I learn today? Only bond anything that is likely to become live in a fault condition. Why present a method of completing a dangerous circuit if there is no reason to do so?

 

[Spark123]

Extraneous conductive parts may not become live under fault conditions however they can introduce a nice path back to earth.
For example if your metalic table lamp had a fault which caused the exposed metalwork to become live (whilst the fault clears - aka Fault protection) and someone was in contact with it and simultaneously an extraneous conductive part they will be in for a belt, hence the reason for main protective bonding of extraneous conductive parts where they enter the equipotential zone.
If they are in contact with the faulty apparatus and an insulated part then the danger is no worse than them not being in contact with it at all.

 

[mikhailfaradayski]

OMG, people are still entertaining burnycock the troll

 

[sparkticus]

Extraneous conductive parts may not become live under fault conditions however they can introduce a nice path back to earth.

They can also become live right? (though less likely I agree) Example a boiler feeding one radiator. Main water feed to boiler in plastic. Boiler in kitchen, radiator in living room. No main protective conductors at gas or water entry points. Boiler electrical supply via standard 13amp plug. Earth within plug not connected or pulled out. Boiler develops earth fault. Boiler chassis live. Radiator in living room live.

If they are in contact with the faulty apparatus and an insulated part then the danger is no worse than them not being in contact with it at all.

Which is similar to contacting an isolated metal radiator (plumbed with plastic pipe)

 

[Spark123]

I sort of get the jist of what you say however the problem there being an exposed conductive part becoming live through not being installed correctly. The radiator isn't really an extraneous conductive part nor the fault something reasonably foreseeable.
Extraneous conductive parts are usually parts which introduce earth potential which can be dangerous owing to potential between them and other extraneous or exposed conductive parts during fault conditions.
Not to say an extraneous conductive part must be at earth potential.

 

[EFLImpudence]

Extraneous conductive parts may not become live under fault conditions however they can introduce a nice path back to earth.

They can also become live right? (though less likely I agree) Example a boiler feeding one radiator. Main water feed to boiler in plastic. Boiler in kitchen, radiator in living room. No main protective conductors at gas or water entry points. Boiler electrical supply via standard 13amp plug. Earth within plug not connected or pulled out. Boiler develops earth fault. Boiler chassis live. Radiator in living room live.

Find a better electrician/plumber.

 

[sparkticus]

Find a better electrician/plumber.

Now that's a good point I can't argue with

 

[sparkticus]

I sort of get the jist of what you say however the problem there being an exposed conductive part becoming live through not being installed correctly. The radiator isn't really an extraneous conductive part nor the fault something reasonably foreseeable.
Extraneous conductive parts are usually parts which introduce earth potential which can be dangerous owing to potential between them and other extraneous or exposed conductive parts during fault conditions.
Not to say an extraneous conductive part must be at earth potential.

Oh yes, I agree with you on all points of course. The scenario I mentioned is highly unlikely, but not impossible especially in my neck of the woods