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

[i=p/u]

Always? Daz

well anything i seem todo, mostly houses these days forn moi daz

 

[i=p/u]

#rcdschangeeverythingandanything.com

 

[bigspark17]

On installs with plastic pipe always run 10mm and ask plumber to install small copper pipe after stop tap and earth to met. Main bonding connected to MET check!!

 

[Midwest]

I have to be honest I don't really understand where 415.2.2 is coming from,
I thought the purpose of supplementary bonding was to keep touch voltages to a minimum, having a resistance of 1667 between an extraneous conductive part and exposed conductive during single fault conditions will surely give rise to a touch voltage approaching the supply voltage?
can someone enlighten me?

thanks

sam

Did you have a look at the vid at#12? The figure 1667 is obtained when the protective device is a 30ma RCD, this figure could be as low as 1.6, if it was B type 6a MCB.

Have a butchers at John Wards vid, it may answer your question, I think; https://www.youtube.com/watch?v=CVxBettQpPU

 

[Midwest]

Sorry, just realised that was a 'Have' and been had!

 

[sam400]

Did you have a look at the vid at#12? The figure 1667 is obtained when the protective device is a 30ma RCD, this figure could be as low as 1.6, if it was B type 6a MCB.

Have a butchers at John Wards vid, it may answer your question, I think; https://www.youtube.com/watch?v=CVxBettQpPU

Thanks for the reply Midwest, I have seen these videos before unfortunately neither of them explain the relationship between the disconnection of a protective device and the resistance between an exposed conductive part and an extraneous conductive part,
Unless Iam missing the obvious! (Quite possible)

The 1.6 ohms comes from R = 50v/30a = 1.667ohms I guess?
How would a live conductor supplied by this 6a MCB come into contact with the Extraneous conductive part (that we have measured) in order to cause this voltage limited disconnection?

 

[Midwest]

Thanks for the reply Midwest, I have seen these videos before unfortunately neither of them explain the relationship between the disconnection of a protective device and the resistance between an exposed conductive part and an extraneous conductive part,
Unless Iam missing the obvious! (Quite possible)

The 1.6 ohms comes from R = 50v/30a = 1.667ohms I guess?
How would a live conductor supplied by this 6a MCB come into contact with the Extraneous conductive part (that we have measured) in order to cause this voltage limited disconnection?

Can't do multi quote, so in answer to your questions.....I think;

1) Bonding, or protective bonding, is an electrical connection maintaining various exposed conductive parts and extraneous conductive parts at substantially the same potential (cited by NIC Snags & Solutions earthing & bonding). If they are not, it could result in electric shock, in the case of a potential fault in an unearthed electrical appliance for example.
2) (1st part) Correct, Ia for overcurrent devices, the corresponding to automatic operation in 5 s (415.2.2). (2nd part) ?? Faulty unearthed appliance connected to water supply (i.e. electric shower), damaged cable placed across metal pipework.

I have a feeling, I've misunderstood your questions?

 

[sam400]

Can't do multi quote, so in answer to your questions.....I think;

1) Bonding, or protective bonding, is an electrical connection maintaining various exposed conductive parts and extraneous conductive parts at substantially the same potential (cited by NIC Snags & Solutions earthing & bonding). If they are not, it could result in electric shock, in the case of a potential fault in an unearthed electrical appliance for example.
2) (1st part) Correct, Ia for overcurrent devices, the corresponding to automatic operation in 5 s (415.2.2). (2nd part) ?? Faulty unearthed appliance connected to water supply (i.e. electric shower), damaged cable placed across metal pipework.

I have a feeling, I've misunderstood your questions?

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

 

[Deleted member 9648]

On installs with plastic pipe always run 10mm and ask plumber to install small copper pipe after stop tap and earth to met. Main bonding connected to MET check!!

I do hope you are joking?

 

[bigspark17]

I do hope you are joking?

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!

 

[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.