Whilst we're on the subject of bonding...

[Midwest]

1) Would you say 1667ohm between extraneous conductive and exposed conductive is at 'substantially the same potential'?

2) So we are testing to see if supplementary bonding is required in case a piece of pipe work becomes live?
historically (16th) supplementary bonding was fitted for the same reason as main protective bonding to reduce the potential between exposed conductive parts and extraneous conductive parts and not to provide a fault path for the disconnection of the protective device?

cheers

sam

1) Less than 1667, is as far as the regs are concerned, if 30ma RCD is used

2) Supplementary bonding, involves the connecting together the conductive parts of electrical & non electrical items, to prevent the occurrence of a dangerous voltage between them under fault conditions. Testing pipe work (in certain locations), is to see whether its 'Extraneous' or not.

 

[Deleted member 9648]

Absolutely not.. Diferent ph levels and salts in water can make it more or less conductive according to levels.. What is stopping the water board putting conductive pipe joint underground and then this becoming extraneous conductive.. Small copper pipe after stop tap earth to MET no PD between earths in installation, tick jobs a good one!

.....On yer' own fella!

 

[Midwest]

I do hope you are joking?

I thought I'd been had, to be honest!

 

[Midwest]

Absolutely not.. Diferent ph levels and salts in water can make it more or less conductive according to levels.. What is stopping the water board putting conductive pipe joint underground and then this becoming extraneous conductive.. Small copper pipe after stop tap earth to MET no PD between earths in installation, tick jobs a good one!

I'm a bit confused by your statement. If you have a plastic incoming water service and plastic property pipework, you would install a piece of copper pipe after stop cock and bond that. Then this will earth the water in the plastic pipe? Or have I got that completely wrong.

 

[sam400]

1) Less than 1667, is as far as the regs are concerned, if 30ma RCD is used

2) Supplementary bonding, involves the connecting together the conductive parts of electrical & non electrical items, to prevent the occurrence of a dangerous voltage between them under fault conditions. Testing pipe work (in certain locations), is to see whether its 'Extraneous' or not.

1) i wouldnt say that two metallic parts that are 1666 ohms apart are at substantially the same potential, despite our interpretation of reg 415.2.2

2)Thats what i don't understand; - having 1666 ohms between an exposed conductive part and an extraneous conductive part during fault conditions will give a voltage approaching mains - depending on the circuit impedance of course.

cheers

sam

 

[bigspark17]

Yes i do.! What do you have against this apart from profit margin, sinks and taps are not plastic even if supplied from plastic pipes! I realise its a bit ott, but if there was ever any change to the supply pipe or if there was a leak external an earth path could exist.! Do you not think water is conductive?

 

[sam400]

Yes i do.! What do you have against this apart from profit margin, sinks and taps are not plastic even if supplied from plastic pipes! I realise its a bit ott, but if there was ever any change to the supply pipe or if there was a leak external an earth path could exist.! Do you not think water is conductive?

Are you getting your water from the atlantic? lol

 

[Midwest]

1) i wouldnt say that two metallic parts that are 1666 ohms apart are at substantially the same potential, despite our interpretation of reg 415.2.2

2)Thats what i don't understand; - having 1666 ohms between an exposed conductive part and an extraneous conductive part during fault conditions will give a voltage approaching mains - depending on the circuit impedance of course.

cheers

sam

1) My science is not too good; if the resistance is too high, then the RCD will not operate. If it's very high, then it's unlikely to matter
2) Can't help you there, perhaps someone more intelligent than me, will be able to answer that

 

[bigspark17]

Are you getting your water from the atlantic? lol

So your saying water is not conductive?

 

[Risteard]

So your saying water is not conductive?

Pure water isn't conductive. It's only the impurities within it which can be.

 

[Midwest]

In reply to #39.

Think we all know that water conducts electricity, that's why we have take extra precautions in special locations. However, my understanding of BS7671, is that we are bonding incoming metal pipes, to prevent them introducing potential. I'm not a scientist, but if in the next edtion of BS 7671, they tell me to bond a plastic water pipe, because the water inside can introduce a potential, then I will.

You should google the subject, here is one such piece of research; http://www.plasticpipesgroup.com/media/1036/earthbonding.pdf

 

[Risteard]

Think we all know that water conducts electricity

Actually, water does not conduct electricity contrary to popular belief.

 

[bigspark17]

Actually, water does not conduct electricity contrary to popular belief.

Well im affraid sir your very wrong!

 

[bigspark17]

In reply to #39.

Think we all know that water conducts electricity, that's why we have take extra precautions in special locations. However, my understanding of BS7671, is that we are bonding incoming metal pipes, to prevent them introducing potential. I'm not a scientist, but if in the next edtion of BS 7671, they tell me to bond a plastic water pipe, because the water inside can introduce a potential, then I will.

You should google the subject, here is one such piece of research; http://www.plasticpipesgroup.com/media/1036/earthbonding.pdf

ok playing devils advocat- why do you earth an installation that is copper pipe for water copper gas, but both incoming gas and water pipes are plastic?

 

[Deleted member 9648]

ok playing devils advocat- why do you earth an installation that is copper pipe for water copper gas, but both incoming gas and water pipes are plastic?

You don't.