Equipotential bonding required for new boiler?

[SUNRAY]

Dont know if anyone else has ever come across bonding to a disabled toilet grab rail? I've seen this done a few times.

Wonder if these bonding fanatics bond the toilet roll holders at home.

I'll repeat that back in the 70's the Leccy board would not connect the power if those things were not bonded in newbuilds.
They would go round with a long test lead and check anything metal, regardless of if it created any electrical hazard.

The builders got very good at timing the connexion way before lots of the doors, windows, coat hooks, metal kitchen cupboard handles, toilet roll holders, towel rails etc etc etc were installed

 

[JohnW2]

I see it as an all, or nothing scenario... You either make sure as much touchable metalwork is bonded, or you make absolutely sure none of it is bonded, and take extra precautions to ensure nothing can accidentally become live, ever. ....

As I implied, it's unfortunately not as simple as that. Like it or not, there are some things (like the L conductors in cables) that have to be 'live'. So, for example, a frayed/damaged lead of a vacuum cleaner can render a life conductor 'touchable'. in which case we have to consider at least two (both incredibly improbable) possible scenarios:

1... the live conductor of the damaged cable touches the metal radiator or bath and, at the same time, someone simultaneously touches that object and something else (e.g. a tap) which is 'earthed' (whether by 'earthing' or 'bonding').​

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2... Someone comes simultaneous in contact with the object and the exposed L conductor of the damaged cable.​

In scenario (1), the person will not get a shock if the object is bonded (or 'earthed) but will get a shock if it is not bonded.
On the other hand, in scenario (2), they WILL get a shock if the object IS bonded (hence earthed), but not if it isn't.

It therefore all depends upon which of the (both incredibly improbable) scenarios one thinks is more likely. Bernard appears to think (1) is more likley, and hence favours bondingf of the object (bath otr whatever). I'm inclined to think the opposite (hence favouring not bonding the object), not the least because (1) required three rather than two, co-incidentally simultaneous 'happenings'

n my home, every bit of touchable metal, which has any chance of becoming live, is carefully bonded. My bath, bath taps, shower, wash-basin, radiator, are all bonded to each other, and to the main earth. My boiler, in the kitchen has the flow, and return pipes bonded, the sink taps, and the radiator. The utility room, the same, except it includes a metal sink, so that is bonded. In other rooms, the radiators, the only fixed metalwork, are also bonded.

As above, if any of your radiators etc. are not otherwise earthed (e.g. because of plastic pipework or well-PTFE-wrapped joints to rad valves) then bonding the radiators would, in certain situations, increase risk. Whether what you've done is sensible therefore would depend upon one's view of whether or not that increased risk is more than balanced by reduction in whatever risk you perceive would be reduced by bonding (hence earthing).

Given that you obviously favour bonding, I would add that if the connections of the rad valves are *(as is common) 'well PTFE wrapped', then bonding of flow to return pipes would probably not result in the radiator itself being bonded/earthed.

 

[Harry Bloomfield]

The radiator example with plastic pipes cannot have any potential - it's just a metal object on the wall.

The only risks, are of someone, perhaps - in the process of fixing the radiator, putting a support bracket fixing screw through a live cable, and thus making the radiator live.

Same applies to a metal door handle or a drawer of metal cutlery.

Likelihood of the door handle, on a wooden door becoming live, absolute zero.

 

[Harry Bloomfield]

It therefore all depends upon which of the (both incredibly improbable) scenarios one thinks is more likely. Bernard appears to think (1) is more likley, and hence favours bondingf of the object (bath otr whatever). I'm inclined to think the opposite (hence favouring not bonding the object), not the least because (1) required three rather than two, co-incidentally simultaneous 'happenings'

Exactly, and if it's not already obvious - I too think 1 is the more likely. I've suffered many more shocks from accidentally live metalwork, than I have had from scenario 2.

 

[JohnD]

I'll repeat that back in the 70's the Leccy board would not connect the power if those things were not bonded in newbuilds.

Might have been a Kent thing?

 

[blup]

The only risks, are of someone, perhaps - in the process of fixing the radiator, putting a support bracket fixing screw through a live cable, and thus making the radiator live.

Wouldn't the introduction of RCD’s have addressed that - intentionally or otherwise?

 

[SUNRAY]

Might have been a Kent thing?

I really don't know but it was a total PITA at the time: wooden windows with metal catches and stays, silver trims on kitchen cupboard doors and drawers, a wooden plate on the wall for a row of coat hooks... oh and remember the fashion for aluminium fronted touch dimmers? it was discovered they didn't work when bonded

 

[EFLImpudence]

The only risks, are of someone, perhaps - in the process of fixing the radiator, putting a support bracket fixing screw through a live cable, and thus making the radiator

So - you would 'bond' the radiator before fixing.

That is not the purpose of bonding; that would be earthing.

 

[JohnW2]

The only risks, are of someone, perhaps - in the process of fixing the radiator, putting a support bracket fixing screw through a live cable, and thus making the radiator live.

True (provided the screw missed the CPC and therefore did not result in an RCD or OPD operating), but that would be even before the radiator was mounted.

If you simply checked that the radiator was not 'live' after you'd attached it to the wall, then I struggle to think of any credible (lert alone 'likely') way in which (if not earthed) it could ever subsequently become 'live'.

Furthermore, as I've said, if (as is common) the radiator were electrically isolated from the pipework by PTFE tape, if you really wanted to earth it, you would have to scrape some paint off thge radiator and use a "radiator earth clamp", such as this ....

 

[JohnW2]

Exactly, and if it's not already obvious - I too think 1 is the more likely.

That's certainly the implication of what you've said you do but, as I've said, our views about this differ.

've suffered many more shocks from accidentally live metalwork, than I have had from scenario 2.

Over the decades, I've had a few 'tingles' from live metalwork (presumably due to capacitive coupling of my body the earth), but I don't think I've ever been simultaneously touching anything earthed, and therefore have not received 'significant shocks' as a result.

As I've just written, provided it is not 'live' when installed, I really can't think of any credible way in which an 'electrically floating' radiator that was not initially 'live' could ever become live - but I can think of some (also incredibly improbable) scenarios in which I might get a significant shock if I touched something else 'live' and simultaneously touch a large bit of earthed metal like a radiator - although maybe the paint would 'save me'

As you (and Bernard) and I illustrate, there is no single 'correct' answer, so I suppose it's a case of "'vive la difference". However, to keep this in context, all of the risks we're talking about are incredibly improbable. People get struck by lightning

 

[ebee]

There are various risks that might vary in intensity and frequency and probability. So we tales what we hope is a sensible approach to cover the majority of scenarios.
I have seen a few times people running extension leads (mains) and popping over radiators and brackets as a temporary approach to keep them tidier, less clutter on the floor, therefore reducing trip hazards. Hopefully the flexes are robust and not damaged and if so then "repaired" require more than a bit of insulting tape wrapped around.
If you know these silly habits and similar daft practices abound with certain people in certain locations you might rebalance your actions and practices slightly in order to reduce the greater risks than otherwise you might not do , one reason is for fear of increasing risks of other dangers.
You start with a (slight) expectation that most people will do most things in a slightly sensible way but where you see some insanities occur do you modify a bit? I think most of us might do slightly in extreme conditions especially if we feel like we are "flogging a dead horse" if we are findinding impossible to educate some common (uncommon) sense. So long as you have considered things and done yer best then what else can you reasonably do. To bond or not to bond has some clear cut groups but also some ifs and buts in some circumstances. You can not absolutely make everyone always safe however much you strive.

Always remember that some folk are stark raving bonkers.

 

[Harry Bloomfield]

Wouldn't the introduction of RCD’s have addressed that - intentionally or otherwise?

Of course, but is it safe to really the point? 30mA can and does still kill.

 

[Harry Bloomfield]

If you simply checked that the radiator was not 'live' after you'd attached it to the wall, then I struggle to think of any credible (lert alone 'likely') way in which (if not earthed) it could ever subsequently become 'live'.

How many individuals do you suppose might carry out such a check? I would not, would you, would a plumber, who installs most of them, even know how?

 

[JohnW2]

How many individuals do you suppose might carry out such a check?

Very few, I imagine, other than those like yourself who were concerned that such may have happened (and therefore felt the need for the radiator to be earthed).

I would not, would you, would a plumber, who installs most of them, even know how?

I certainly wouldn't and nor do I imagine that many people would. However, if you felt that, in the absence of such a check, you would want/need to explicit earth the radiator (increasing risk in some circumstances), then I probably would expect you to do it.

 

[JohnW2]

There are various risks that might vary in intensity and frequency and probability. So we tales what we hope is a sensible approach to cover the majority of scenarios.

Quite so.

I have seen a few times people running extension leads (mains) and popping over radiators and brackets as a temporary approach to keep them tidier, less clutter on the floor, therefore reducing trip hazards. Hopefully the flexes are robust and not damaged and if so then "repaired" require more than a bit of insulting tape wrapped around. ... If you know these silly habits and similar daft practices abound with certain people in certain locations you might rebalance your actions and practices slightly in order to reduce the greater risks than otherwise you might not do , one reason is for fear of increasing risks of other dangers.

Indeed. If one felt that there was an appreciable probability that such practices would occur in a particular case, then mitigating that risk would be sensible - but I'm not sure how one could come to the conclusion that such happenings were more likely than the other possible happenings that would lead to the opposite conclusion (about the desirability of the radiator being earthed.

Don't forget that even if a radiator were to become 'live' due to reasons such as you suggest, it would only represent a serious risk if someone managed to simultaneously touch it and something that was earthed (which may not exist within arm's reach of the radiator)

In terms of what is "sensible" (or even 'necessary') we need to remember that the risks with either approach are not far from zero!

Furthermore, Harry has yet to clarify whether he really has earthed his radiators, rather than just the pipework. I've just tested a couple of the radiators in my (all copper plumbing) house, and they appear to not be earthed, even though the pipework is earthed, presumably due to the PTFE tape.

Kind Regards, John