2 circuits done. 2 to go.

[ebee]

So we need to keep domestic wiring to what the ordinary person will expect to find, and not expect them to know the difference by looking at a cable between 4 mm² and 2.5 mm² even in commercial premises I have found a 4 mm² radial split and extra sockets added as if it was a ring final with 2.5 mm².

However, only someone competent should messing about with electrics in the first place . As Clint (Dirty Harry) Eastwood says "Each Man should know his limitations" - whether Electrics or car brakes etc etc.

Of course, we all know what happens in the real world

 

[JohnW2]

.... even in commercial premises I have found a 4 mm² radial split and extra sockets added as if it was a ring final with 2.5 mm².

What's wrong with that?

Kind Regards, John

 

[JohnW2]

The Ring Final in your home is meant to be all or nothing in normal service, it is a final circuit. However say you have (Switched or Unswitched) Fused Connection Units (Sometimes wrongly referred to as "Spurs") then the Ring Final Circuit is actually the distribution circuit feeding those.

That's almost become 'semantic'.

I would think that it would only really be a 'distribution circuit' if one took the BS7671 definition of 'a circuit' literally and believed that an FCU created a new ('final') circuit. However, that would not seem to be the intention (at least, of the legislation), since it would mean that adding an FCU to a ring final would be notifiable - something which was (explicitly) not even the case before the major relaxations of notification rules (in England) in 2013 (and still applicable in Wales).

Furthermore, I'm not sure that, even if one did regard the FCU as creating a 'new circuit', the main circuit would be correctly described as a 'distribution' one - since distribution circuits, essentially by definition, don't have multiple socket outlets along their length!

Kind Regards, John

 

[ericmark]

Now your moving into English comprehension, a bit of wiring protected by an overload device is a circuit, but once you have a final circuit there can't be any more circuits.

So a central heating boiler supplied from a FCU its self on a ring final, is not forming another circuit for the central heating, the whole of the ring final is the circuit.

I am sure when central heating manufactures say all 230 volt parts within the system should be supplied from the same circuit/supply they mean same FCU or 13 amp plug, but that is not what they are saying.

Same when a FCU supplies a number of 13 amp sockets from a ring final it can't be a new circuit as final is clearly in English the last circuit.

But common sense must prevail.

 

[JohnW2]

Now your moving into English comprehension, a bit of wiring protected by an overload device is a circuit, but once you have a final circuit there can't be any more circuits. ... So a central heating boiler supplied from a FCU its self on a ring final, is not forming another circuit for the central heating, the whole of the ring final is the circuit.

As many of us have said in the past, that is, indeed, common sense, but it seems to contradict what you have tried to argue in the past - that, on the basis of the BS7671 definition of 'a circuit', an FCU does create a 'new circuit'.

Kind Regards, John

 

[SUNRAY]

"My understanding is a ring main is designed so sections can be isolated for work to be done, and the cable used can take the current permitted by the protection device.

The ring final however should not be broken, and was designed with the fused plug to save copper after WW2.

Other than both forming rings, they are nothing like each other."

Agreed, A Ring Main say at a power station is designed with conductors the csa of a radial, if there is isolation each side of any component then the rest of the set up carries on as a radial (actually two radials) all good so far. Or you could isolate a group of adjacent components, those would all be isolated and the remainder still in use.

I agree that one operational idea of a ring main is the ability to add isolators at various points and that type of circuit was (I believe but very happy to be corrected/contradicted) installed on Titanic and very common in military shipping. However the isolation points have never been a requirement.

The Ring Main in the street is to mitigate volt drop so is sometimes wired as such.

Indeed as I described at my first house however I believe ring mains in the street are not common

The Ring Final in your home is meant to be all or nothing in normal service, it is a final circuit. However say you have (Switched or Unswitched) Fused Connection Units (Sometimes wrongly referred to as "Spurs") then the Ring Final Circuit is actually the distribution circuit feeding those.

So if every point on the ring circuit were to be a spur powered by a FCU and by definition (or general acceptance?) each individually protected spur would then be a new circuit. Would you not then consider the feeding ring is actually a ring main feeding a series of fused spurs/radials just as used to feed DBs around an installation?

 

[ericmark]

Shows I do listen to what you and others say, as to the boiler, that is a hard question, we are trying to guess why it says things like should be supplied from the same supply? One point is they tend to call the extra low voltage to a thermostat low voltage, so in spite of references to BS 7671, seems the person who has written the instruction set has not read BS 7671. Or it is some feeble attempt to use what they consider is the English used by the general public, who knows which?

So we are left trying to understand why if the power supply is built into the thermostat we need to get that power from the same point as the boiler, but if separated as with Nest we can get the supply from any point that we can plug the USB adaptor into.

If we want all supplied by same fuse, since often there is a fuse in the boiler, then the supply would need to come from the boiler, connecting to same FCU would not help, idea is it is claimed turn off boiler and all is isolated.

As long as the thermostat has volt free contacts I see no real problem, however there has been a tendency for plumbers not to run enough cores, and common to find them using a green/yellow wire as line.

Again it is the English "The bi-colour combination green-and-yellow shall be used exclusively for identification of a protective conductor and this combination shall not be used for any, other Purpose.
(Note the full stop, it seems plumbers choose not to see the full stop, which changes what is said as it continues)
Single-core cables that are Coloured green-and-yellow throughout their length shall only be used as a protective conductor and shall not be over-marked at their terminations, except as permitted by Regulation 514.4.3."

I am sure they are fully aware what they are doing is wrong, the people who write BS 7671 keep changing the wording to remove any ambiguity. But laws need the courts to clarify, which means there has to be a court case, so until there is, and there may have been one, although we think they should have called the device a distribution unit so it covers units over 100 amp which have not been type tested, they used the word consumer unit.

I am sure those who try to claim it was not a consumer unit as some thing they did removed the type testing, know very well that is not in the sprite of the law, in the same way as saying if we use a consumer unit instead of a FCU on a garage supply it needs the work registering.

But some and I must include myself can get a bit pedantic. In the main as we have come to expect people to pick us up on our errors.

I some times think the regulations work against people getting things right. We should say you need to do ABC oh and by the way the work should be registered. Not don't do this work is needs registering as it stops people learning how to do it safely. We all know they will DIY, does not matter how much you tell them they are breaking laws or rules, or assume they are doing it correct, and suggest they ask their inspector what he will accept.

 

[JohnW2]

So if every point on the ring circuit were to be a spur powered by a FCU and by definition (or general acceptance?) each individually protected spur would then be a new circuit.

As I've said, that was eric's original argument - and he was literally correct in terms of the BS7671 definition of 'a circuit'; - but, as i also said, it is clearly not was intended by those who wrote the 'notification rules'.

Would you not then consider the feeding ring is actually a ring main feeding a series of fused spurs/radials just as used to feed DBs around an installation?

We're now down to pure semantics/terminology. If, despite the above, one did consider each FCU to be creating a 'new circuit', the the ring would then certainly be a 'distribution circuit' (in the form of a ring). Whether or not one would/could call it a 'ring main' is a different matter, given that it is (as far as I aware) not a term which has ever been used (or, I suspect, intended to be used) to describe something within an electrical installation.

Kind Regards, John

 

[JohnW2]

Shows I do listen to what you and others say, as to the boiler, that is a hard question, we are trying to guess why it says things like should be supplied from the same supply?

I wouldn't say that one has to guess. Is it not probably fairly obvious why they are saying that - i.e. because they want there to be a 'single point of isolation' for the ("230V" supply to) the boiler and all associated components of the heating system?

As for "why it says ...", what is the "it" you are referring to? Perhaps I have missed it, but I can't think of any regulation which actual says what you refer to - rather, it is something which one often reads in MIs for boilers.

Again it is the English "The bi-colour combination green-and-yellow shall be used exclusively for identification of a protective conductor and this combination shall not be used for any, other Purpose.
(Note the full stop, it seems plumbers choose not to see the full stop, which changes what is said as it continues)
Single-core cables that are Coloured green-and-yellow throughout their length shall only be used as a protective conductor and shall not be over-marked at their terminations, except as permitted by Regulation 514.4.3."

I'm not sure what this has got to do with the current discussion, but I don't really get your point, since the two sentences relate to different things.

As you are aware, the usage of conductors can be identified by the colour of their intrinsic insulation ('throughout their length") OR by the colour of over-sleeving at the ends (which 'over-rides the insulation colour). The first sentence says that G./Y can only ever be used 9as insulation colour or over-sleeving) a protective conductor, but it does not say that, in general, a G/Y insulated cable cannot be over-sleeved with some other colour to indicate a use other than as a protective conductor. Hence, as we know, although most of us don't like the idea, it is permitted to over-sleeve a G/Y-insulated conductor in a multiple-conductor cable with, say, brown, to indicate that it vis being used as a live (actually line/phase) conductor.

The second sentence qualifies the first, by saying that, in the specific case of a G/Y-insulated conductor in a single-core cable, it is not permitted to use it as anything other than a protective conductor (i.e. cannot be over-sleeved to identify some other use.

I don't see that the fact that these are two sentences separated by a full-stop is relevant, and I'm not sure in which way you think plumbers may mis-read/misunderstand this reg (by 'not seeing the full stop). Perhaps you can clarify?

I some times think the regulations work against people getting things right. We should say you need to do ABC oh and by the way the work should be registered. Not don't do this work is needs registering as it stops people learning how to do it safely. We all know they will DIY, does not matter how much you tell them they are breaking laws or rules, or assume they are doing it correct, and suggest they ask their inspector what he will accept.

I suspect you really mean 'notification' (or the legislation which requires notification) rather than 'regulations' - for example, people in wales might litter their kitchen floors with extension leads because they don't want to incur the nitrification requirement involved with installing extra sockets OR those who intend to undertake notifiable work without notification may be hesitant to ask for advice about how to do it properly/safely. If so, I agree with you that, in those sort of senses, the requirements for notification (much more in Wales than in England0 may be somewhat counter-productive in terms of safety.

Kind Regards, John

 

[SUNRAY]

We're now down to pure semantics/terminology. If, despite the above, one did consider each FCU to be creating a 'new circuit', the the ring would then certainly be a 'distribution circuit' (in the form of a ring). Whether or not one would/could call it a 'ring main' is a different matter, given that it is (as far as I aware) not a term which has ever been used (or, I suspect, intended to be used) to describe something within an electrical installation.

Kind Regards, John

But the term ring main has been in use for a century and in printed documents.
I'm sure you would not hesitate to use the term 'sub main' to describe a cable from an OCPD to a dis board, what else would you call it if it was a ring feeding several disboards?

 

[JohnW2]

But the term ring main has been in use for a century and in printed documents.

In relation to something within a (domestic or commercial) electrical installation.

I'm sure you would not hesitate to use the term 'sub main' to describe a cable from an OCPD to a dis board,

Agreed. It may not be correct, but I think I would use either 'sub main' or ';distribution circuit', interchangeably

what else would you call it if it was a ring feeding several disboards?

I've never heard of a distribution circuit (or 'submain') within an installation being wired as a true ring, and nor can I really see why that would be done (other, I suppose, than for reasons similar to those mentioned in relation to true 'ring mains' in a DNO's distribution network), so it's not a question I've ever had to consider.

All I can do is repeat what I said before, that I have personally never heard to term 'ring main' being used 'correctly' (i.e. other that erroneously, when referring to a ring final circuit) in relation to something within an installation. Has anyone else?

Kind Regards, John

 

[ebee]

So if every point on the ring circuit were to be a spur powered by a FCU and by definition (or general acceptance?) each individually protected spur would then be a new circuit. Would you not then consider the feeding ring is actually a ring main feeding a series of fused spurs/radials just as used to feed DBs around an installation?

Can`t argue with that

 

[SUNRAY]

So if every point on the ring circuit were to be a spur powered by a FCU and by definition (or general acceptance?) each individually protected spur would then be a new circuit. Would you not then consider the feeding ring is actually a ring main feeding a series of fused spurs/radials just as used to feed DBs around an installation?

Can`t argue with that

Now I'll take a step back and describe circuits in my house as a ring where every point where current can be drawn is fused, so yes it is still actually a ring main by the old original parameters.

Taking another step back I'll also add the regs are not law (as others keep mentioning) and any circuit may be designed by an installer. As long as it does not contravene the regs there can be no objection to it. Such as rings for 6A lighting circuits which of course is not listed in the regs and therefore doesn't have a name.

However I will generally use the description ring final as those are the words used in the book.

 

[JohnW2]

Now I'll take a step back and describe circuits in my house as a ring where every point where current can be drawn is fused, so yes it is still actually a ring main by the old original parameters.

As others have said, I can't really argue with that, although I can again point out that (even if it fulfils the definition) I have never personally seen the term "ring main' used in relation to wiring within a domestic (or commercial) installation (other that {commonly!} 'incorrectly' to refer to a ring final circuit per BS7671)

Taking another step back I'll also add the regs are not law (as others keep mentioning) and any circuit may be designed by an installer. As long as it does not contravene the regs there can be no objection to it. Such as rings for 6A lighting circuits which of course is not listed in the regs and therefore doesn't have a name. However I will generally use the description ring final as those are the words used in the book.

As you imply, there is nothing in BS7671 which prevents one returning 'the end' of any ('radial') circuit back to the OPD, thereby turning it into a ring but, other in the specific instance of the BS7671-defined ring final, there would very rarely be any point (if cable CCC were not adequate, one would be better off just using fatter cable).

In terms of 'CPC redundancy' (the one 'advantage' of any ring), if one really wanted to one could achieve that by taking just a CPC (not L or N) from the end of the circuit back to the MET/whatever, thereby having a CPC ring, but no L or N rings.

The whole point of the specific BS7671-defined ring final circuit, is that it is a 'dispensation' which allows one to 'break the rules' of other regs, by using a cable with a CCC less than the In of the OPD. One could not do it if the circuit were supplying something other than 'accessories to BS1363' and/or if the OPD was something other than 30/32A.

Kind Regards, John

 

[SUNRAY]

The whole point of the specific BS7671-defined ring final circuit, is that it is a 'dispensation' which allows one to 'break the rules' of other regs, by using a cable with a CCC less than the In of the OPD. One could not do it if the circuit were supplying something other than 'accessories to BS1363' and/or if the OPD was something other than 30/32A.

Kind Regards, John

That's not quite clear cut, parallel feeding is permitted, as is downstream protection.
Ironically parallel feeding with 2x2.5mm² could potentially be with a 50A OCPD