Is 24KΩ just a standard value or is it calculated? GN8 provides an equation and a number of standard figures depending on what the designer wants the level of current through the body not to be exceeded.
Water pipe bonding
- Thread starter davecooper
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- bonding water pipe
10mA is regarded as the threshold -- see edit
240/0.01 = 24000
You may use 48kΩ for 5mA if you wish but, as I said, the decision is not likely to have to be made between 23999 and 24001 or, indeed 48001.
It will likely be a few ohms or Mega ohms.
Edit - threshold of being able to let go.
240/0.01 = 24000
You may use 48kΩ for 5mA if you wish but, as I said, the decision is not likely to have to be made between 23999 and 24001 or, indeed 48001.
It will likely be a few ohms or Mega ohms.
Edit - threshold of being able to let go.
I did make a mistake - see edit
That's an easier calc than
RCP>(UO/IB)-ZT
Which comes out as an RCP of 22K for 10mA
RCP>(UO/IB)-ZT
Which comes out as an RCP of 22K for 10mA
Well, they piddle about with nominal voltage, i.e. minus 10V (which as Winston will tell you, it probably won't be) then they subtract 1000Ω for the body's resistance (which varies) (10/0.01=1000 so back to square one).
As it's not critical you may as well use the maximum voltage and whatever current you decide relevant.
As it's not critical you may as well use the maximum voltage and whatever current you decide relevant.
Just to add that this is a commercial premises, and to confuse me more, someones now said, that EAW regs say the metal pipes need bonding.
However I since heard the fit out spec stated All copper OR All plastic, possibly due to this bond or not to bond dilemna, so looks like it will all be replaced eventually, though till then, I assume we will end up running the bond and strap on the incoming pipe for now.
Back in the day i recall you strapped across both sides of gas meters, however now its just consumer side, isnt it, surely that too could be pointless, if the meter and flexipipe are poor conducters, by it being load side it gives me the impression, that its more likely to bond the loadside, rather than the incoming extraneous bit that I thought was the intention, or am I more confused
However I since heard the fit out spec stated All copper OR All plastic, possibly due to this bond or not to bond dilemna, so looks like it will all be replaced eventually, though till then, I assume we will end up running the bond and strap on the incoming pipe for now.
Back in the day i recall you strapped across both sides of gas meters, however now its just consumer side, isnt it, surely that too could be pointless, if the meter and flexipipe are poor conducters, by it being load side it gives me the impression, that its more likely to bond the loadside, rather than the incoming extraneous bit that I thought was the intention, or am I more confused
That depends what they mean by 'need'.
Yes.
I believe, with gas meters, the gas company do not want their incoming pipe to carry any current, so they fit an insulating section.
However, this does not actually alter anything from the electrical aspect
Bonding the consumer side is not required, if isolated from the ground. However, gas pipes are likely to be earthed in the premises so it doesn't really matter.
Their pipe should still be bonded but they don't want it to be. They should insulate it.
This does not apply to the water supply, of course.
Not exactly sure what you mean.
The extraneous-c-p is all that requires (main) bonding; it doesn't matter what happens to the rest inside.
I've only just noticed this thread ....
If I 'obeyed' that regulation, as written, in my house, I would be left with about 6 metres of easily touchable, but not bonded, extraneous-c-p (a metal pipe) in my cellar (between the pipe's entry into the premises and the {insulating} meter) - which could represent a potentially lethal hazard.
Kind Regards, John
It does indeed state that - and, as has often been discussed here, I think that all it tells us is that whoever wrote it does not have even the most basic of understanding of the meaning and purpose of Main Equipotential Bonding (or PEB, or whatever you want to call it).
If I 'obeyed' that regulation, as written, in my house, I would be left with about 6 metres of easily touchable, but not bonded, extraneous-c-p (a metal pipe) in my cellar (between the pipe's entry into the premises and the {insulating} meter) - which could represent a potentially lethal hazard.
Kind Regards, John
So john, can I assume your bonded at the point of entry of the 6 metre pipe.
Is it all plastic after that pipe
Is it all plastic after that pipe
Yep. That's what MEB/PEB requires, even if the regs don't
No plastic pipe anywhere, but the meter is insulating. With the original meter, they put a puny little strap across it (2.5mm, if that) but when they last changed the meter, they even removed that
Kind Regards, John
Ok thanks, think ive got it, so at the sinks or anywhere did you feel the need to crossbond the pipes
No. Supplementary Bonding is not required in a kitchen, anyway -
and from your description would introduce hazards where none exists at present by creating negligible impedance paths to earth on isolated parts.
and from your description would introduce hazards where none exists at present by creating negligible impedance paths to earth on isolated parts.
If that is a response to my preceding post, then it relates to a totally different issue from what I was talking about (main equipotential bonding).
When you talk of 'cross-bonding', what do you mean - Supplementary Bonding (which joins extraneous-c-ps to exposed CPs, and is now only {sometimes} required in bathrooms, and usually not even in bathrooms), or literally just bonding together of pipes, without any connection to CPCs (hence exposed-c-ps)?
Kind Regards, John
As you imply, Supplementary Bonding (which involves connection of extraneous-c-ps to exposed-c-ps) is now only ever required in bathrooms, and even there not very often.
However, as I've just written, I wonder whether that's what Rocky was talking about or whether, rather, he was talking about just 'cross-bonding' pipes (without any {'G/Y'} connection to CPCs). When there is an all-metal plumbing system, I would think that never makes sense. However, I think it's a bit different if the plumbing system is partially plastic. Even when there is some plastic pipework, at least some of the metal pipework will be connected to earth, either incidentally (via immersions, CH valves/motors etc.) or by virtue of main bonding, whereas, as you imply, some may be 'floating'. In that situation, I can see an argument for 'cross-bonding' (simply joining pipes together with G/Y) simultaneously-touchable metal pipes, if one is 'floating and the other connected to earth in some way - because, although very unlikley, it is not impossible that the 'floating' pipe could somehow become 'live' by virtue of contact from some 'live' part or cable.
Kind Regards, John
No.
There's no such thing, electrically, as cross-bonding.
Quite frankly, I can't believe you wrote it. I thought I had dissuaded you from earthing isolated metal parts.
There's no such thing, electrically, as cross-bonding.
Quite frankly, I can't believe you wrote it. I thought I had dissuaded you from earthing isolated metal parts.