The spoon would become live and introduce a shock hazard to anyone retrieving the spoon. So what is the correct way to bond the spoon? Also, some of my spoons are a metal end on the wooden handle, do these still need to be bonded?
To bond or not to bond..?
- Thread starter flyingsparks
- Start date
The spoon would become live and introduce a shock hazard to anyone retrieving the spoon. So what is the correct way to bond the spoon? Also, some of my spoons are a metal end on the wooden handle, do these still need to be bonded?
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This is obviously all very silly but, since it certainly would not be an extraneous-conductive part, the spoon would certainly not need to be bonded. If anything were done to the spoon it would be to earth it, but even that is obviously totally silly and impossible!
Kind Regards, John
I wouldn't like to go as far as to say impossible. I'd envisage perhaps a coiled wired, like a phone receiver, that attaches to the spoon and an earthing point on the ceiling. It does of course create the dilema of how to put the spoons in the dishwasher. Perhaps the answer is the hand wash the cutlerly, as with Teflon coated cookwear?
To talk about spoons, doorknobs etc. in this context is obviously totally stupid.
However as you will presumably be aware, there is much more scope for serious debate in relation to metal baths, metal workbenches etc.
Kind Regards, John
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would anyone in their right mind create a metallic path between some metal outside the house and the Live conductor inside the house. ?
No they wouldn't.
Then consider that the Neutral is often considered to be a live conductor.
Then consider that it is possible and does happen that the Neutral coming into the house may be driven above true ground by a fault in the network.
Earthing and Bonding may be different functions for different purposes but the metallic connection creating by them is the same. There is nothing different electrically between bonding and earthing unless there is something clever in the cable that prevents ground potential going into the building and when there is a fault prevents Live potential going out of the building.
The risk if a Neutral fault is low but not zero so there is a risk that bonded pipework going through the wall to the outside will be dangerously above ground potential. That is probably the reason why electric tools to be used in the garden have to be double insulated and are not provided with the ability to be earthed.
Or would it be bonding of the green/yellow core as it enters the building to prevent it introducing an extraneous potential ( ground ) into the building.
No they wouldn't.
Then consider that the Neutral is often considered to be a live conductor.
Then consider that it is possible and does happen that the Neutral coming into the house may be driven above true ground by a fault in the network.
Earthing and Bonding may be different functions for different purposes but the metallic connection creating by them is the same. There is nothing different electrically between bonding and earthing unless there is something clever in the cable that prevents ground potential going into the building and when there is a fault prevents Live potential going out of the building.
The risk if a Neutral fault is low but not zero so there is a risk that bonded pipework going through the wall to the outside will be dangerously above ground potential. That is probably the reason why electric tools to be used in the garden have to be double insulated and are not provided with the ability to be earthed.
Or would it be bonding of the green/yellow core as it enters the building to prevent it introducing an extraneous potential ( ground ) into the building.
Quite (although obviously one sometimes has to deal with such paths which already exist) - that's why I didn't (and still don't) understand your apparent agreement with eric's "if in doubt, bond" approach, even when the bonding is unnecessary.
Of course, in practice, the discussion is often moot. In the case of 'just an Aga', it is very possible that the oil pipeline could be, and be left, floating. However, if the oil pipe connects to a boiler (as will very often be the case), then it is almost inevitable that it will thereby become connected to the installation's CPCs and exposed-c-ps ('earth'), whether one likes it or not (unless one took steps to 'electrically interrupt') the pipe.
Kind Regards, John
Electrically interrupting would, indeed, be a good solution, if anyone wanted to do that, although, of course, it is not allowed for gas pipes and so no one bothers with water or oil pipes.
This would then lead to having to distinguish between pipes which were extraneous and those not, so, as it is now, as they are all likely to be connected to the CPCs bonding is done to all as it will not make the situation worse which negates the need to understand.
Indeed. As for gas pipes, we're increasingly seeing external meters fed by plastic pipe. However, even with those, a good few electricians seem to continue to interpret the regs (incorrectly, IMO) as requiring them to bond the copper pipe from the meter where it enters the premises [I say 'incorrectly' since, if it's not an extraneous-c-p, it does not require main bonding].
Indeed - that's what I said. However, as I also said, an oil pipe supplying only an Aga could be an exception - in which case bonding it could, theoretically, "make the situation worse" (both for people inside and outside of the premises).
Kind Regards, John
Plumbers (inspecting boiler) will never accept the absence of a G/Y wire no matter what.
Perhaps we shall have to attach one that doesn't go anywhere.
That is correct.
I was away from the BGB this morning when Eric wrote:
"As we look at the risks therefore there are risks either way bond or not to bond so we tend to hide behind 411.3.1.2 and bond."
and wasn't sure which was 411.3.1.2.
However, I am not sure what hiding behind there is as it clearly states that:
"...main protective bonding ... shall connect to the MET extraneous-c-ps including the following:
<various parts>"
People either seem to ignore the preceding sentence or think the list is a list of extraneous parts.
It could.
Quite so. Similarly, I presume that the same people probably interpret 544.1.2 as saying (which it doesn't) that "any gas, water or other service" has to have main bonding, even if it is not an extraneous-c-p.
Mind you, as we've often discussed, even the person(s) who wrote 544.1.2 did not seem to understand the concept of main equipotential bonding, since that regulation is explicit in calling for bonding on the customer's side of an 'insulating section or insert' in a service pipe - even though one is thereby applying 'main equipotential bonding' to something which cannot possibly be an extraneous-c-p!
Kind Regards, John
My understanding is that the advent of PMR type supplies came about for two reasons.
[1] it reduces the cost of the network by removing the third wire. The earth wire that was NOT connected to neutral but was true ground at the substation.
[2] it could ensure that flats and other premises that were not at ground level had an "earth" that was adequate for safety without having to depend on a cable down through some one else's property.
The problems arise in situations where the artificial "earth" ( the neutral ) and real earth ( the ground ) could become connected via a person ( hence not exporting the PME earth to gardens tools ) or a length of cable that could over heat if the current from neutral to the ground became too high ( when the network neutral rises above ground potential.
[1] it reduces the cost of the network by removing the third wire. The earth wire that was NOT connected to neutral but was true ground at the substation.
[2] it could ensure that flats and other premises that were not at ground level had an "earth" that was adequate for safety without having to depend on a cable down through some one else's property.
The problems arise in situations where the artificial "earth" ( the neutral ) and real earth ( the ground ) could become connected via a person ( hence not exporting the PME earth to gardens tools ) or a length of cable that could over heat if the current from neutral to the ground became too high ( when the network neutral rises above ground potential.
Quite so - albeit that bit of un-bonded extraneous-c-p is usually sufficiently hidden-away/'inaccessible' as to not pose a significant hazard. However, it does underline the fact that the author(s) of 544.1.2 do not seem to really understand what theoretically does, and does not, require MEB!
Kind Regards, John
That sounds credible. The 'third wire' (or metal sheathing/whatever) of TN-S obviously IS connected to neutral, but only at the same place (the substation) where the neutral is connected to true earth. As an additional maintenance/cost issue, I suspect that failure of TN-S earths (with L&N still intact and, in themselves, serviceable) was/is quite common.
If you're comparing with TT that makes some sense. However, I don't see that it really represents a significant advantage of TN-C-S over TN-S. With TN-S, the L&N obviously have to get to the upper-floor flats, anyway, so to also take the earth is not much of an issue, is it?
Kind Regards, John
Three wires cost 50% more than two wires
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