A bit of bondage!

[EFLImpudence]

It is pointless arguing with Cockburn but the way this thread is going several of you are in danger of ending up agreeing with him.

Bonding is not applied to ensure operation of the CPD.

 

[sparkticus]

Totally agreed. As for your example, as you will have seen, despite the flak and/or ridicule it generates everytime I mention it (sometimes with comparisons between me and the main protagonsit of this thread!), I'm a great believer in having electrical continuity between any metallic parts that can be simultaneously touched, regardless of what the regs may say. If I'm confident that continuity exists because of, say, metallic pipework which I know is always going to be there, then I'm happy with that. If not, out comes the G/Y cable!

John, I don't disagree with you on continuity between metallic parts that might become live.

Where would you draw the line though? Would you place a G/Y on a radiator that is plumbed with a few meters of plastic pipe?

If so, what would you do with a large metal shelf that is permanently fixed to the the wall say 150mm from the radiator?

 

[EFLImpudence]

Metal parts which may become live...

...do not include those which may be touched by a live wire someone is waving around because they have managed to 'get hold of' it.

They are those which may become live because of a fault in an appliance and will be connected to a CPC.

 

[sparkticus]

Metal parts which may become live...

...do not include those which may be touched by a live wire someone is waving around because they have managed to 'get hold of' it.

That is my understanding and I would not attempt to provide a means of continuity between those metal parts to the MET or attempt to make them any more equipotential than they actually are by nature since they are essentially floating. I include a metal radiator plumbed in plastic pipe in that statement.

They are those which may become live because of a fault in an appliance and will be connected to a CPC.

Agreed.

 

[JohnW2]

John, I don't disagree with you on continuity between metallic parts that might become live.
Where would you draw the line though? Would you place a G/Y on a radiator that is plumbed with a few meters of plastic pipe?
If so, what would you do with a large metal shelf that is permanently fixed to the the wall say 150mm from the radiator?

Hardly an answer, but 'where I draw the line' is a matter of common sense (as I see it), decided on a case-by-case basis according to the situation. As others have said, 'unnecessarily' bonding exposed metal can create more potential hazards than the vanishingly unlikely hazards they might theoretically reduce. So, in terms of the specifics you mention, unless there were other factors at work, I would not want to bond either the radiator or shelf.

As you will have seen, some of the most heated arguments seem to relate to metal baths and kitchen sinks (in the presence of plastic plumbing - since, otherwise, 'G/Y bonding' is essentially moot). In those situations, it's swings and roundabouts. The idiot who runs an extension lead into a bathroom, uses a hair dryer or CD player and then drops it into the bath of water in which their naked body is residing might be saved by bonding. Same for (s)he who drops a mains powered mixer into a kitchen sink full of water that they are touching. However, the person who touches a sink and a kettle at the moment it develops a L-E fault could be killed by bonding. If not only because it's doing no more than creating the same situation that exists in the (very common, even today) 'all metal pipe household', I probably would incline towards bonding in those situations - but I agree that it's a debatable issue. What would you do, if it were your home?

Kind Regards, John.

 

[Paul_C]

If not only because it's doing no more than creating the same situation that exists in the (very common, even today) 'all metal pipe household', I probably would incline towards bonding in those situations

As did the IEE in the past, since earlier editions of the Wiring Regs. made it clear that these were expected to be bonded. But they did also include radiators in the list.

 

[sparkticus]

Hardly an answer, but 'where I draw the line' is a matter of common sense (as I see it), decided on a case-by-case basis according to the situation. As others have said, 'unnecessarily' bonding exposed metal can create more potential hazards than the vanishingly unlikely hazards they might theoretically reduce. So, in terms of the specifics you mention, unless there were other factors at work, I would not want to bond either the radiator or shelf.

Actually I think that is a perfectly reasonable answer and approach.

As you will have seen, some of the most heated arguments seem to relate to metal baths and kitchen sinks (in the presence of plastic plumbing - since, otherwise, 'G/Y bonding' is essentially moot). In those situations, it's swings and roundabouts. The idiot who runs an extension lead into a bathroom, uses a hair dryer or CD player and then drops it into the bath of water in which their naked body is residing might be saved by bonding. Same for (s)he who drops a mains powered mixer into a kitchen sink full of water that they are touching. However, the person who touches a sink and a kettle at the moment it develops a L-E fault could be killed by bonding. If not only because it's doing no more than creating the same situation that exists in the (very common, even today) 'all metal pipe household', I probably would incline towards bonding in those situations - but I agree that it's a debatable issue. What would you do, if it were your home?

Yes, I would agree here also. I would lean on the side of not bonding provided I was certain that there were no possibility of the metal parts becoming live from fixed wiring (including the flex from FCUs)

I do have the partial plastic plumbing arrangement throughout my house and where I was absolutely sure of fixed safe cable proximity away from radiators then I have not bonded. In other area's at the combi for example everything (flow, return, gas, hot DHW, cold feed) are interconnected with 6mm G/Y. They are of course interconnected via the mass of the boiler frame anyway but I still bonded. I also have 10mm G/Y from gas/water to the MET. So the majority of my metal plumbing is equipotential and at the same potential as the MET (give or take a few millivolts of volt drop of course)

 

[JohnW2]

Actually I think that is a perfectly reasonable answer and approach.

It's nice to hear that someone agrees with me!

Yes, I would agree here also. I would lean on the side of not bonding provided I was certain that there were no possibility of the metal parts becoming live from fixed wiring (including the flex from FCUs)

It sounds as if we agree about the fact that this is a grey area with swings/roundabouts, even though our considered views appear to be leaning in opposite directions. However, I do not see that as a problem - that's what 'grey areas' are all about.

Kind Regards, John.

 

[JohnW2]

If not only because it's doing no more than creating the same situation that exists in the (very common, even today) 'all metal pipe household', I probably would incline towards bonding in those situations

As did the IEE in the past, since earlier editions of the Wiring Regs. made it clear that these were expected to be bonded. But they did also include radiators in the list.

If my understanding is correct, what was arguably a bit daft was that in the essentially pre-plastic-plumbing era, the regs required bonding of things which were quite clearly connected by something with a far greater CSA than the required bonding conductors.

Kind Regards, John.

 

[sparkticus]

It sounds as if we agree about the fact that this is a grey area with swings/roundabouts, even though our considered views appear to be leaning in opposite directions. However, I do not see that as a problem - that's what 'grey areas' are all about.

If the grey area is a small proportion of the white area I don't think it's too big a problem either provided "competent persons" are also "intelligent persons" and "thinking persons"

 

[Paul_C]

If my understanding is correct, what was arguably a bit daft was that in the essentially pre-plastic-plumbing era, the regs required bonding of things which were quite clearly connected by something with a far greater CSA than the required bonding conductors.

Not back in the 14th edition:

D.14 The exposed metalwork of all apparatus which is required by these Regulations to be earthed, which might otherwise come into fortuitous contact with extraneous fixed metalwork shall be either effectually segregated therefrom or effectually bonded thereto so as to prevent appreciable voltage differences at such possible points of contact (see also Regulation B.53).

NOTE 1. - The extraneous fixed metalwork required to be bonded and earthed in these circumstances includes the following:

(i) Baths and exposed metal pipes, radiators, sinks and tanks, in the absence of metal-to-metal joints of negligible resistance. {.....}

 

[sparkticus]

Not back in the 14th edition:

That's the pre-cockburn period, a simpler, primordial period where ELCBs roamed mostly in the pastures of the TT highlands.

 

[JohnW2]

Not back in the 14th edition:

Thanks. That's a bit more sensible, then.

Kind Regards, John

 

[JohnW2]

If the grey area is a small proportion of the white area I don't think it's too big a problem either provided "competent persons" are also "intelligent persons" and "thinking persons"

Exactly.

My worry, and I think also yours, is that the 'definition' of a "competent person" does not seem to include any requirments in relation to intelligence or thinking ability - or, as we have both often noted, a good understanding of the underlying principles.

Kind Regards, John.

 

[sparkticus]

My worry, and I think also yours, is that the 'definition' of a "competent person" does not seem to include any requirments in relation to intelligence or thinking ability - or, as we have both often noted, a good understanding of the underlying principles.

Historically correct but changing for the better from 2012. How much better I don't know, jury out on that one.