Radiator earth bonding

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This is just a question to satisfy my curiosity. As it is getting cooler I decided to clean dust balls from the middle of my radiators. They are,of course,earth bonded,(the rads.,not the dust balls :D)but each bonding has a couple of feet of cable, coiled and cable tied, shoved up inside the rad. So why ? I would expect a small loop to avoid strain,but not this much.
 
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It is not clear from the description, but if I understand correctly, I would assume the installer did not want to cut it.

Radiators do not require bonding; the pipes might.
 
It goes from a clamp on the pipe to a little clamp on the edge of the radiator, bridging the thermostat connections. He had to cut it at some point,so why coil up 40 inches (just measured one),tie with a tie and shove it up the inside of the rad.? Times 9 of them is about 24 feet of excess earth cable.
 
It goes from a clamp on the pipe to a little clamp on the edge of the radiator,
That is not necessary as bonding.

bridging the thermostat connections.
Not sure what that means.

He had to cut it at some point,so why coil up 40 inches (just measured one),tie with a tie and shove it up the inside of the rad.? Times 9 of them is about 24 feet of excess earth cable.
I have no idea why people do strange things.
 
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from a clamp on the pipe to a little clamp on the edge of the radiator, bridging the thermostat connections.
Do you mean the thermostatic valve / TRV?

Radiator valves are metal, the radiator is already electrically connected to the pipes.
The clamps and wire are 100% unnecessary and entirely pointless.
 
...and if the valves were not metal and the radiator were NOT electrically connected to the pipes, it would be better left that way.
 
yes I mean the TRV,by bridged I mean from the pipe to the rad,across the fittings that connect those things. My thinking was that the metal should make a good electrical connection,even if PTFE is used,as that only fills the gaps,if any,between the threads. This was done by a large company refurbing a council estate when this was a council house about 15 years ago. Obviously the guy who did it was not paying for his own cable. If they are unnecessary they can come off,as they trap even more carp between the radiator panels.I have an RCD on sockets and shower,fitted at the same time during a rewire.
 
Yes, they can be removed.


If metal parts are earthed by contacting other parts which are earthed then they are earthed.

If metal parts are NOT earthed by contacting other parts which are earthed then that is better and safer.
Connecting them would not be bonding but earthing unnecessarily and introducing a hazard.



Also, do not earth your cutlery.
 
If metal parts are NOT earthed by contacting other parts which are earthed then that is better and safer. Connecting them would not be bonding but earthing unnecessarily and introducing a hazard.
It wouldn't surprise me if that statement confused some people a bit, since I think it could be taken to imply that most/all true bonding was, in fact, 'earthing'.

If one uses a bit of G/Y cable to join a radiator/pipe/whatever to a nearby CPC/exposed-c-p, that would normally be taken to be 'supplementary bonding' (whether or not it was required/needed), rather than 'earthing', wouldn't it?

Kind Regards, John
 
It wouldn't surprise me if that statement confused some people a bit, since I think it could be taken to imply that most/all true bonding was, in fact, 'earthing'.
Is that just because some people will be confused or do you mean I have worded it poorly?

If one uses a bit of G/Y cable to join a radiator/pipe/whatever to a nearby CPC/exposed-c-p, that would normally be taken to be 'supplementary bonding' (whether or not it was required/needed), rather than 'earthing', wouldn't it?
I'm surprised you ask.

Not if that radiator/pipe/spoon is isolated, not an exp-c-p nor ext-c-p, and will have no potential and therefore will never need its potential equalising, so any G/Y wire earthing it will be earthing.

Part 2 Definitions

"Bonding conductor: A protective conductor providing equipotential bonding."

"Equipotential bonding: Electrical connection maintaining various exposed-conductive-parts and extraneous conductive-parts at substantially the same potential."
 
Is that just because some people will be confused or do you mean I have worded it poorly?
I meant that you had worded it in such a manner that some people might be confused.
... I'm surprised you ask. Not if that radiator/pipe/spoon is isolated, not an exp-c-p nor ext-c-p, and will have no potential and therefore will never need its potential equalising, so any G/Y wire earthing it will be earthing.
That's why I added "(whether or not it was required/needed)". You are talking about whether or not there is a need/requirement for bonding. However, if a G/Y conductor is connected between two things with the intent of ensuring that there could never be an appreciable PD between them, then I would call that 'bonding' (by virtue of the intent), whether or not there was any obvious way in which such a PD could arise (hence an actually 'need' for bonding), and regardless of whether one, both or neither of the connected parts had a low impedance path to earth.

As you are aware, the intent of 'earthing' is totally different - namely to facilitate the operation of a protective device in the event of a fault. As such, it relates to what may happen to one ('exposed') 'part', not to potential differences between two of them.

Kind Regards, John
 
I meant that you had worded it in such a manner that some people might be confused.
I think any wording would do that.

That's why I added "(whether or not it was required/needed)". You are talking about whether or not there is a need/requirement for bonding. However, if a G/Y conductor is connected between two things with the intent of ensuring that there could never be an appreciable PD between them, then I would call that 'bonding' (by virtue of the intent), whether or not there was any obvious way in which such a PD could arise (hence an actually 'need' for bonding), and regardless of whether one, both or neither of the connected parts had a low impedance path to earth.
Mistaken intent and mistaken result.

As you are aware, the intent of 'earthing' is totally different - namely to facilitate the operation of a protective device in the event of a fault. As such, it relates to what may happen to one ('exposed') 'part', not to potential differences between two of them.
This misplaced wire cannot be to equalise potential if one or neither part has no potential, therefore it is not bonding. The part might introduce a potential after wrongly earthing it, so it might then also require bonding.

However, were an isolated part to be unnecessarily earthed then it would operate the protective device should a live conductor contact it. So for this reason also, it must be earthing whichever semantics you are employing.


Part 2 Definitions

"Earthing: Connection of the exposed-conductive-parts of an installation to the main earthing terminal of that
installation."


Perhaps the relevant definitions for this are "Unnecessary" and "Hazardous".

It really is helpful to think of this metal part as if it were a spoon.



 
This misplaced wire cannot be to equalise potential if one or neither part has no potential, therefore it is not bonding. The part might introduce a potential after wrongly earthing it, so it might then also require bonding.
I didn't say that it was to equalise the potential between two things, one or both of which had (when examined) no potential but, rather, to ensure that they never could have (in whatever circumstances) significantly different potentials.

One has to remember that bonding is required if a part is "liable to introduce a potential". That is different from "does introduce a potential" and requires judgment of what 'might' happen, rather than on what could be measured at any particular point in time.

I've mentioned before my gas (LPG) supply pipe which turns from plastic to metal within, and then travels through, a deep pile of gravel (resting on soil) before entering my house (cellar) below ground level. For 99% of the time is it essentially electrically 'floating' (and therefore not introducing any potential), as your measurements would indicate. However, I regard it as 'liable to' introduce a potential (earth potential), and therefore have main-bonded it, since the gravel will occasionally become waterlogged, creating a semi-conductive path to the soil below. Would you not have bothered to bond it?

I have another, perhaps better, example in my workshop, where there are two adjacent, but not touching, metal-topped (wooden) work benches. Both are normally electrically 'floating', and I certainly have not 'earthed' them, since I would regard that as creating an unnecessary hazard. However, I have (electrically) 'bonded' them together since, despite what some people might suggest, it would not require 'two faults' for a hazard to arise - it would only need one 'happening' and one fault, the 'happening' being that a Class I item (without a fault) was resting on one of them. In this case, I see nothing wrong with (or, really, any alternative to) describing it as 'bonding', even though neither part normally has any potential, since the purpose is to ensure that there are never significant PDs between the parts, and one certainly couldn't call it 'earthing', since there is no 'earth' involved at all! Would you call it something different from 'bonding'.

Kind Regards, John
 
I didn't say that it was to equalise the potential between two things, one or both of which had (when examined) no potential but, rather, to ensure that they never could have (in whatever circumstances) significantly different potentials.
Ok, but would you do it if neither is liable to introduce a potential?

One has to remember that bonding is required if a part is "liable to introduce a potential". That is different from "does introduce a potential" and requires judgment of what 'might' happen, rather than on what could be measured at any particular point in time.
That is less likely than introducing a permanent negligible impedance path to earth which might cause one to have a severe shock.

I've mentioned before my gas (LPG) supply pipe which turns from plastic to metal within, and then travels through, a deep pile of gravel (resting on soil) before entering my house (cellar) below ground level. For 99% of the time is it essentially electrically 'floating' (and therefore not introducing any potential), as your measurements would indicate. However, I regard it as 'liable to' introduce a potential (earth potential), and therefore have main-bonded it, since the gravel will occasionally become waterlogged, creating a semi-conductive path to the soil below. Would you not have bothered to bond it?
Up to you but a 1% chance of that is surely better than the now 100% chance of causing the above.
Not going to happen to an isolated radiator though.

I have another, perhaps better, example in my workshop, where there are two adjacent, but not touching, metal-topped (wooden) work benches. Both are normally electrically 'floating', and I certainly have not 'earthed' them, since I would regard that as creating an unnecessary hazard.
Good - so what is the difference?

However, I have (electrically) 'bonded' them together since, despite what some people might suggest, it would not require 'two faults' for a hazard to arise - it would only need one 'happening' and one fault, the 'happening' being that a Class I item (without a fault) was resting on one of them. In this case, I see nothing wrong with (or, really, any alternative to) describing it as 'bonding', even though neither part normally has any potential, since the purpose is to ensure that there are never significant PDs between the parts, and one certainly couldn't call it 'earthing', since there is no 'earth' involved at all! Would you call it something different from 'bonding'.
I suppose you are bonding them in the English meaning of the word but not by what we usually mean by Main or Supplementary bonding and not in the sense of any requirement of the regulations, but surely you are doing a Bernard and guarding against the Blue Moon event rather than the more likely events when you would not want them joined.
 
Ok, but would you do it if neither is liable to introduce a potential?
No, I wouldn't, since there would be no point (like bonding two spoons together :) ). However, I think this has become a discussion about what "liable to" means. I take it to mean 'could'/'might' (under certain circumstances), whereas you seem to take it to mean 'does now'. I suspect that we may have to 'agree to disagree' about that one.

I must say that I would argue that my interpretation seems more consistent with the reg's definition of an extraneous-c-p. If they meant a conductive part which did "introduce a potential, generally Earth potential" (which is what you would determine, for one point in time, by your testing), wouldn't it just say that, rather than "liable to"?
That is less likely than introducing a permanent negligible impedance path to earth which might cause one to have a severe shock.
You can't really say that as a generalisation, since it depends totally upon how likely the "liable to" event actually is.
Up to you but a 1% chance of that is surely better than the now 100% chance of causing the above.
It's not a 100% chance of having a severe shock - it's a 100% chance of that shock happening IF someone simultaneously touched it and something else which (due to a fault) was live, at the very time that fault was present, which is an extremely unlikely occurrence.

The problem is that, as so often, we are talking about, and try to compare, two minute risks. If one (a) omitted all (required) main bonding OR (b) earthed every bit of fixed metal in a house (I'll let you off the spoons and forks :) ) then, in either case, I would think that the probability of anyone suffering a severe shock as a result would be incredibly small (since it requires not only a fault, but a victim who is unlucky enough to be touching 'the wrong two things' at the very time the fault is present), wouldn't you?

... but are you actually saying that, if you saw my metal LPG pipe entering my cellar about 18" below ground level, you would not bond it because when you 'measured it' (during a dry period) it had a very high resistance/impedance to earth?
Good - so what is the difference?
That's what the rest of my paragraph (which you didn't quote) went on to explain ....
I suppose you are bonding them in the English meaning of the word but not by what we usually mean by Main or Supplementary bonding and not in the sense of any requirement of the regulations ....
I agree that it's not BS7671's meaning of Main or Supplementary bonding, and is not a requirement, but it's a common concept in relation to the wider scope of electrics and electronics. For example, the 'wrist strap and fly lead' worn by people handling static-sensitive electronics is a form of equipotential bonding.

... but surely you are doing a Bernard and guarding against the Blue Moon event rather than the more likely events when you would not want them joined.
Am I? Is what I am 'guarding against' any more of a 'Blue Moon event' than the possible (but incredibly unlikely) events that concern you in relation to 'unnecessarily earthed metal'?? As above, the real problem is that we are all talking about incredibly unlikely events - but that's also what many of the regs are designed to 'guard against'.

In fact, I would say that the thing I am 'guarding against' in my workshop is essentially the same thing that you are 'guarding against' when you advise against 'unnecessarily earthing' things. I am considering the (far from uncommon) situation in which one of the metal bench tops is at earth potential (because a Class I item is sitting on it) and a fault arises in something on the other bench, rendering it 'live'. Very unlikely, I agree, but I don't think any less likely than the situation you are contemplating, is it? In your situation, you can advise against the deliberate earthing of the metal. However, in my workshop I can't do that, since any earthing is incidental/accidental - but what I can do is ensure that the two bench tops could not (in the event of a fault) come to have significantly different potentials.

Kind Regards, John
 

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