Bond sinks and mains water with plastic at start

[radiohead]

this is where i get really confused. im going to get somwone to do the job anyway but for my own sanity is there an explicit definition of "extraneous metal part"? i thought it was a conductive "thing" that enters the location (house) which may introduce a separate connection to earth and therefore may have different potential to MET. in my case this is ONLY the gas pipe (assuming its metal) but NOT my water main as that is plastic at point of ingres to the house. BUT then the gas pipe connects to boiler along with all CH pipes so are those, up to any point at which they become isolated by plastic pipe are also extraneous?Is then the hot water pipe from copper cylinder are also extraneous along with any water pipe that has a conductive path eg.copper hot water pipe to brass tap mixer which in turn has copper connection to cold water pipe.... and so on? my head hurts

There is no need to be confused, it really is very simple and you are rather over thinking it. An extraneous conductive part is defined as a metallic part which is not part of the electrical installation but which may introduce a potential, usually earth.
Consider a 'normal' building. Floors walls and ceilings are generally constructed of materials with a high resistance and low conductivity. An external metallic service entering the building is likely to introduce an earth potential by virtue of being in contact with the ground, so it is main bonded to the MET at the point of entry, beyond this point any metallic pipework is likely to be within the confines of an electrically insulated building and so should not pick up an external potential. The hazard has been dealt with at the point of entry, it matters not what any pipework does within the building from an electrical point of view. The common misconception that bonding is to prevent pipework becoming 'live' is totally incorrect. Other requirements are in place to prevent that, such as wiring being kept apart from other services. Where a conductive part such as an immersion heater, or motorised valve is connected to metallic pipework the pipe will be earthed because it is physically connected to the conductive part, and so will be protected against a fault to earth, but that is not the same as bonding.
Supplementary bonding is an additional measure only likely to be required in special locations, which do not include kitchens. I cannot think of a single instance where bonding a kitchen sink would be required. Even if the sink was tested and found to be extraneous it is almost certain that whatever the sink was attached to (pipe...structural steel etc) would be extraneous...NOT the sink. And of course an incoming metallic pipe or structural steel will have been or should have been main bonded anyway.
Far too much is made of testing to see if something is extraneous. It is nearly ALWAYS possible to ascertain whether bonding is required simply be observation of building structure and incoming services. Testing is nearly always misleading because of parallel paths. For example consider testing a heating pipe. It is likely to to be physically but indirectly connected to a gas service which whether bonded or not will be 'earthy'. The gas service will clearly need bonding, but a test may show the heating pipe should also be bonded. Simple observation will show the gas pipe is coming in from externally, in contact with the ground and will require bonding, but the heating pipes are completely within the confines of the building and cannot introduce an external potential.

 

[radiohead]

Have you tested the sink to see if it requires bonding?
'

Someone else who doesn't understand bonding.

 

[DPG]

Someone else who doesn't understand bonding.

I think he does. I think he was doing the same as me - pointing the OP towards what might be extraneous and what can't be.

 

[radiohead]

I think he does. I think he was doing the same as me - pointing the OP towards what might be extraneous and what can't be.

Doesn't seem much point in pointing the OP to test something which will not require bonding but which the suggested test may indicate to the OP that it should be bonded. Just going to confuse him more.

 

[DPG]

Doesn't seem much point in pointing the OP to test something which will not require bonding but which the suggested test may indicate to the OP that it should be bonded. Just going to confuse him more.

Not so much test it, but to consider why theres no point bonding it.

 

[LastManOnline]

thx all. i understand there is no longer a requirement to bond kitchen sink or water pipe if plastic entering building. but if this metal is not now extraneous (outside building) AND not exposed conductive part of part of electrical installation iit can sit there unbonded and become live in fault condition? Does this mean no overcurrent device (mcb) would operate neither earth leakage ( rcd). ONLY when somone grounded that faulty live metalwork would the fuse/ mcb or rcd operate? we laughed back in day when 15th edition said to bond everything but this does seem rather odd! I will leave the sink bond in then BUT is there a reason (safety) why I shouldnt? i appreciate its not in regs.

"To Bond or not to Bond ,that is the question".

I wonder if there is another forum in the world outside the UK and ROI that gives this topic the level of attention we do.I may be corrected by my UK colleagues here ,but I dont believe there is.I have worked in a number of countries in Europe and beyond and the amount of " green/yellow" cable bonds I have seen is a small fraction of what we are used to seeing here.

Your point about the 15th th edition being regarded as OTT in relation to bonding is well made.Over here in the ROI we have just being informed that as of february 2021 we are no longer required to bond sinks ( no that is not a misprint.It really is 2021 ,not 2001). Despite the fact that they have being plumbed in plastic since the 1990,s.
I personally have being banging on the inspectors doors for a number of years in relation to the isssue. What gets to me is the fact that we now have arbitrary regs about either bonding or not bonding sinks , when in reality its the electrical principle of " is it extraneous or not " that should always be the determining factor.

 

[Sadsyndrome]

Reading about this for a while now. Still none the wiser about whether bonding is required in bathroom or when. At least I know kitchens and water mains with plastic at point of Ingres don’t need it (I’m going to leave it in for now though.

Read on one forum that there was a Poor unfortunate girl sat on sink (earthed) put hand in toaster current flowed and girl died. Wow. Very sad.not sure whether it’s true.

Conversely, if a strange fault occurred making unearthed sink live someone could get shock from it. I have rcd protection on all circuits so guess I need not worry too much.

Either case is very unlikely but in case of the poor girl this was the reality. I suppose all this earthing stuff is about mitigating risks however unlikely it be.

 

[Sadsyndrome]

There is no need to be confused, it really is very simple and you are rather over thinking it. An extraneous conductive part is defined as a metallic part which is not part of the electrical installation but which may introduce a potential, usually earth.
Consider a 'normal' building. Floors walls and ceilings are generally constructed of materials with a high resistance and low conductivity. An external metallic service entering the building is likely to introduce an earth potential by virtue of being in contact with the ground, so it is main bonded to the MET at the point of entry, beyond this point any metallic pipework is likely to be within the confines of an electrically insulated building and so should not pick up an external potential. The hazard has been dealt with at the point of entry, it matters not what any pipework does within the building from an electrical point of view. The common misconception that bonding is to prevent pipework becoming 'live' is totally incorrect. Other requirements are in place to prevent that, such as wiring being kept apart from other services. Where a conductive part such as an immersion heater, or motorised valve is connected to metallic pipework the pipe will be earthed because it is physically connected to the conductive part, and so will be protected against a fault to earth, but that is not the same as bonding.
Supplementary bonding is an additional measure only likely to be required in special locations, which do not include kitchens. I cannot think of a single instance where bonding a kitchen sink would be required. Even if the sink was tested and found to be extraneous it is almost certain that whatever the sink was attached to (pipe...structural steel etc) would be extraneous...NOT the sink. And of course an incoming metallic pipe or structural steel will have been or should have been main bonded anyway.
Far too much is made of testing to see if something is extraneous. It is nearly ALWAYS possible to ascertain whether bonding is required simply be observation of building structure and incoming services. Testing is nearly always misleading because of parallel paths. For example consider testing a heating pipe. It is likely to to be physically but indirectly connected to a gas service which whether bonded or not will be 'earthy'. The gas service will clearly need bonding, but a test may show the heating pipe should also be bonded. Simple observation will show the gas pipe is coming in from externally, in contact with the ground and will require bonding, but the heating pipes are completely within the confines of the building and cannot introduce an external potential.

Thanks?. I’m only trying to understand it so probs am overthinking it. However, if you take a look around at the many forums where the topic has been discussed you will see that it may not be as clear to many people as it is to you

 

[LastManOnline]

However, if you take a look around at the many forums where the topic has been discussed you will see that it may not be as clear to many people as it is to you

I am a relative newcomer to this forum myself and its standard of teaching is in my humble opinion second to none. Ever being involved in discussions where you feel you are just "going around in circles"?. Or you ask a question only to end up with 2 more questions rather than an answer?
You have arrived on a site where the "ifs, buts and maybys" are gradually taken out of the equation through sound logical reasoning. You already experienced that from the replies on this thread. Take a look at the older posts on the same topic. Believe me, in a matter of weeks your uncertainties about bonding will be history

 

[Sadsyndrome]

I certainly hope so. Although I only started looking at this as I’m just about to refurb bathroom and also want to change CU. Once I’ve done those I guess my involvement in electrical work will cease. As it turns out I cannot legally do the latter in a cost effective manner, so will either have to abandon that and keep my plastic enclosure, single rcd for all circuits system, or get someone in to do it. The supplementary bonding in bathroom still confuses me as on another forum with quotes from regs, it appears supp bonding cannot be omitted without main equipotential bonding I’ll have a rest and take another look at that later.

Thanks for clarifying “extraneous” as that was confusing me. Btw Is extraneous in a special location the same or is it extraneous to the location, in my case bathroom?

 

[loz2754]

Extraneous in this context means not part of the electrical installation.

 

[Midwest]

Thanks for that it is one I had seen . It says at 2.00 that any less than 1667ohms no bonding required (assuming rcd 30ma). At the end it says less than .02MOhms you do need to bond and above you don’t? Both say measure Between Known earth in the room and lump of metal you want to know whether to bond or not.

He said that between below 0.02mohms and above 1667ohms, would need bonding. However, bear in mind the accuracy of using IR tester of measuring ohms.

I don’t agree with not testing to discover if something is extraneous or not though. It depends on the property. In my three year old house, all pipework is plastic, except the internal gas, and short pieces of copper to shower valves. So no reason to test. But in older houses, with all copper pipes, with routes unknown unknown, such a test is the only way to confirm IMO.

 

[LastManOnline]

Thanks for clarifying “extraneous” as that was confusing me. Btw Is extraneous in a special location the same or is it extraneous to the location, in my case bathroom?

"extraneous" technically is defined as metalwork that could "introduce a potential" usually earth potential. I have also noticed that some forums have applied it in its dictionary sense of "originating from outside". However electrically speaking metalwork "originating from outside" but that "cannot introduce a potential" is not what is electricians consider as extraneous. You can simplfy the matter for yourself by simply carrying out an IR test on the metalwork in question. Isolated metalwork will likely give either an "infinity" or an extremely high megaohm reading. Metalwork that gives a lower reading (30,000 ohms for instance) though technically "extraneous" is not required to be bonded in UK as that resistance is deemed too high to allow a dangerous shock to occur. I believe the cutoff point in UK to be around 22,000 ohms. I, m sure other posters will confirm

 

[LastManOnline]

"extraneous" technically is defined as metalwork that could "introduce a potential" usually earth potential. I..

Apologies to previous posters. I had, nt read through all the comments and ended up repeating some of what had already been stated.

 

[DPG]

Apologies to previous posters. I had, nt read through all the comments and ended up repeating some of what had already been stated.

Worth repeating. As you say, a lot of people dont understand the while bonding thing.

 

[ipf]

Earthing and Bonding.....here we go. It's a case of having a read and sort out the difference between them. As indicated, find some old threads on the subject.

Back to the 15th..... Earthing? Just bond it....he, he! ?

Remember taking earth wires from the nearest point to bond radiators, for example.



Wrong with this sketch...you'd have to unplug the kettle to reach the tap and refill it, thus eliminating the problem.
It's a guide, by the way, not the actual regs.

 

[Sadsyndrome]

He said that between below 0.02mohms and above 1667ohms, would need bonding. However, bear in mind the accuracy of using IR tester of measuring ohms.

I don’t agree with not testing to discover if something is extraneous or not though. It depends on the property. In my three year old house, all pipework is plastic, except the internal gas, and short pieces of copper to shower valves. So no reason to test. But in older houses, with all copper pipes, with routes unknown unknown, such a test is the only way to confirm IMO.

I would like to test for interest more than anything as I have a 1986 house with copper pipe throughout but with some plastic additions that I have made over the years. However all CH pipes are connected to bonded gas main pipe via boiler and copper hot water tank. Assuming the flexible hoses ( ones with steel braiding) are conductive then the cold water pipes are connected to hot water pipes via those through the mixer taps, apart from útil room where I used plastic flex is for some reason. So electrically the whole copper pipe system will be at same potential (met bonded to gas). That’s without the current bond on the cold water main (no longer required apparently as it is plastic incomer) and the cross bonding between hot and cold that exists under sink in útil room and also by stop cock. Therefore without disconnecting these pipes and “bonds” the test would be pointless as the reading to MET will be very low. Oh and one other point which would make testing difficult, I don’t own a IR or MFT tester? given I have to get someone in to test whatever work is done so I’m not going to fork out for one now As I have to spend that money on a more modern up to date sparks than me shame that I like new toys.