two ring mains joined

[ban-all-sheds]

Indeed it isn't. However, 433.1.204 appears to be saying that a ring final ("with or without unfused spurs") may be wired in cable with a CCC of 20A

That is not saying that the spurs may necessarily be wired using cable with a CCC of 20A. People are quite happy to use cable with a lower CCC when the spur is fused - they don't take the phrase "with or without unfused spurs" to mean that fused ones must use "20A cable", so where on earth is the sense in thinking that unfused ones must?

"Thinking" is the word on which to focus.

and the guidance in Appendix 15 suggests that such a spur may supply a double socket. Since that cable may well only be protected from overload by two 13A fuses (downstream), unless the designer has a crystal ball which can tell him/her that the load will never be >20A, such a circuit would be non-compliant with other regulations.

And there you have it. We do not need the regulations changed so that they explicitly re-state requirements, over and over and over again to cater for people who cannot or will not think about the fact that all relevant ones always apply all of the time in every situation. We need designers to actually understand what they are doing.

It therefore seems as if only 'the dispensation' as regards ring finals (and spurs therefrom) allows what would otherwise (without that crystal ball) be non-complaint if it were, say, a 20A CCC cable supplying just one double socket as a 32A radial.

There is no dispensation from 433.1.1 for the spur cable.

or do you perhaps believe that a 32A radial supplying one double socket, wired in cable with a CCC of 20A, would be compliant?

What's the design current?

 

[scousespark]

The IET may share the same view that causes me never to contemplate deliberately installing such a circuit - namely that I fear that a substantial proportion of electricians would probably not be able to properly test or fault-find such a circuit.
Kind Regards, John

You appear to have the lowest opinion of electricians that I have come across. To the extent you have stated that yourself, and a select few other atypical diyers, should be regarded as equal to trained/qualified/experienced electricians - despite having no training, qualifications or provable experience. Are you now seriously saying you believe the people behind the regs omit things because mere electricians would not be able to undertand what was written?

Some of us actaully know what the numbers on our test equipment represent and can even (I know you won't believe this) understand what is happening in the circuit we are testing. Of course, as you have NEVER met an electrician with anywhere near your grasp of all things electrical, you won't believe a word of this. If I came across this circuit in a test, I'd note it but not code it. If I was asked to work on it, I'd only do so after removing the interconnection. If you would do differently, then that's fine. I am happy interpreting the regs, using the OSG and Guidance Notes where appropriate.

 

[ban-all-sheds]

If, as has been stated, it is 'safer' than a standard ring it must, surely, be compliant.

No, it must not.

Feel free to design it, identify it as a departure, and show what you have done in your design to satisfy yourself that it is no less safe than something which complies with the Regulations.

But do not claim that it must comply, because clearly it does not.

To counter Bas's reason for dismissing it by saying it is not a ring, could it be argued that it is, indeed, not A ring but two or three rings each of which in its own right complies with the requirements.
That is, any one of them would still be satisfactory as A ring were the others disconnected from it.

They don't, and only one would be were the other(s) removed.

Read the definition in Part 2. Consider what happens if you remove the top ring here:

 

[JohnW2]

You appear to have the lowest opinion of electricians that I have come across.

That's simply not true. As in all walks of life, I'm sure that there are some 'bad' electricians', and some 'exceptionally good' electricians, with the vast majority being somewhere in-between - but that's not what I was talking about. I was referring to the fact that a lot of electricians will not have been trained to test, and will have little, if any, experience of testing, circuits of the type we were discussing, and that not all of them will inevitably find it easy to work out for themselves how that testing should be done.

To the extent you have stated that yourself, and a select few other atypical diyers, should be regarded as equal to trained/qualified/experienced electricians - despite having no training, qualifications or provable experience.

If you believe that I have stated or claimed that, either I expressed myself very badly or you misunderstood. As you say, I have no training or qualifications, and little experience. What may be true is that I, and a few other non-electricians, have an understanding of the principles involved (and 'the regulations') which is comparable with that of many electricians - but that in no way makes me "equal to" a trained, qualified and experienced electrician.

Are you now seriously saying you believe the people behind the regs omit things because mere electricians would not be able to undertand what was written?

I am saying that I could understand "the people behind the regs" being hesitant to 'promote' a type of circuit which required appreciably more complex testing than most electricians have been taught to undertake, or have been called upon to undertake. However, that is pure speculation, and there are countless other reasons why they might no want to 'promote' such a circuit - particularly given that they are probably under some pressure to disallow ring circuits of any type.

Some of us actaully know what the numbers on our test equipment represent and can even (I know you won't believe this) understand what is happening in the circuit we are testing. Of course, as you have NEVER met an electrician with anywhere near your grasp of all things electrical, you won't believe a word of this.

Sarcasm is not necessary, and will not help your argument. Of course I accept that many electricians have a very good understanding of what their test results mean and "what is happening" in the circuit concerned.

If I came across this circuit in a test, I'd note it but not code it.

That seems very reasonable, but I presume that is not all that you would do. Detecting the presence of a cross-link is the start, but, having detected it, I presume that you would then take the necessary steps to confirm that there was satisfactory continuity (of L, N and CPC) within each of the 'sub-rings' - since, if any such continuity was absent/unsatisfactory, I imagine that you probably would feel the need to 'code' it. That additional testing obviously can be done, although it is appreciably more complex than the testing that most electricians are used to, but it probably is not often taught, and does not appear in, for example, GN3.

As I said, this whole discussion started because a significant proportion of electricians appear to believe that a cross-connection in a ring is non-compliant - and therefore should, in itself, be 'coded'.

If I was asked to work on it, I'd only do so after removing the interconnection. If you would do differently, then that's fine.

I would probably do the same, just as I would never deliberately install such a circuit in the first place - primarily because I don't want to make life more difficult/confusing than it need be for anyone who may work on the circuit in the future.

Kind Regards, John

 

[JohnW2]

It therefore seems as if only 'the dispensation' as regards ring finals (and spurs therefrom) allows what would otherwise (without that crystal ball) be non-complaint if it were, say, a 20A CCC cable supplying just one double socket as a 32A radial.

There is no dispensation from 433.1.1 for the spur cable.

As I said, I'm not so sure about that ...

Accesories to BS1363 may be supplied though a ring final circuit, with or without unfused spurs, protected by a 30A or 32A .... Such circuits are deemed to meet the requirements of Regulation 433.1.1 if the current-carrying capacity (Iz) of the cable is not less than 20A ....

It is easy to read that to mean that an unfused spur is part of "such circuits", in which case a spur cable with an Iz ≥20A would be deemed to satisfy 433.1.1. You will undoubtedly disagree.

or do you perhaps believe that a 32A radial supplying one double socket, wired in cable with a CCC of 20A, would be compliant?

What's the design current?

That's essentially the question I was asking you. Given that the downstream over-current protection could be provided by 2 x 13A fuses, and given that very few of the general public have any reason to believe that they should not plug in 2 x 13A loads, I personally think it would be questionable to regard the design current as anything less than 26A. I personally certainly wouldn't install a circuit such as I have described - would you?

Kind Regards, John

 

[EFLImpudence]

Accesories to BS1363 may be supplied though a ring final circuit, with or without unfused spurs, protected by a 30A or 32A .... Such circuits are deemed to meet the requirements of Regulation 433.1.1 if the current-carrying capacity (Iz) of the cable is not less than 20A ....

It is easy to read that to mean that an unfused spur is part of "such circuits", in which case a spur cable with an Iz ≥20A would be deemed to satisfy 433.1.1. [/QUOTE]
I read that to mean that the spurs are separate from the rest of the requirements.

 

[EFLImpudence]

Read the definition in Part 2. Consider what happens if you remove the top ring here:

If I have understood correctly, this is the configuration:

 

[JohnW2]

Accesories to BS1363 may be supplied though a ring final circuit, with or without unfused spurs, protected by a 30A or 32A .... Such circuits are deemed to meet the requirements of Regulation 433.1.1 if the current-carrying capacity (Iz) of the cable is not less than 20A ....

It is easy to read that to mean that an unfused spur is part of "such circuits", in which case a spur cable with an Iz ≥20A would be deemed to satisfy 433.1.1. /QUOTE]
I read that to mean that the spurs are separate from the rest of the requirements.

If that is the intended interpretation, then BAS is presumably right, and a cable with CCC of 20A may not (depending upon one's view of 'design current') be adequate to satisfy 433.1.1 for an unfused spur feeding a double socket. However, even if that were their intent, I suspect that many people probably interpret it in the manner I suggested.

Kind Regards, John

 

[JohnW2]

If I have understood correctly, this is the configuration: .... [/ATTACH]

Although we haven't really been given enough information to know one way or the other, I have to say that I had been assuming that the configuration was as suggested by BAS, rather than your interpretation.

Kind Regards, John

 

[ban-all-sheds]

It is easy to read that to mean that an unfused spur is part of "such circuits", in which case a spur cable with an Iz ≥20A would be deemed to satisfy 433.1.1. You will undoubtedly disagree.

or do you perhaps believe that a 32A radial supplying one double socket, wired in cable with a CCC of 20A, would be compliant?

What's the design current?

That's essentially the question I was asking you. Given that the downstream over-current protection could be provided by 2 x 13A fuses, and given that very few of the general public have any reason to believe that they should not plug in 2 x 13A loads, I personally think it would be questionable to regard the design current as anything less than 26A. I personally certainly wouldn't install a circuit such as I have described - would you?

Kind Regards, John[/QUOTE]

Accesories to BS1363 may be supplied though a ring final circuit, with or without unfused spurs, protected by a 30A or 32A .... Such circuits are deemed to meet the requirements of Regulation 433.1.1 if the current-carrying capacity (Iz) of the cable is not less than 20A ....

It is easy to read that to mean that an unfused spur is part of "such circuits", in which case a spur cable with an Iz ≥20A would be deemed to satisfy 433.1.1. You will undoubtedly disagree.

It is easy to read it that way, and I do disagree that " the cable " means the spur one(s). It's worth noting that the problems you see with spur cables not having explicit prescriptions within 433.1 arise because you are reading it that way and because you have decided that the other regulations disallowing such a cable on such an OPD do not apply.

But to an extent any disagreement is irrelevant because that problem is generic to all socket circuits.

That's essentially the question I was asking you. Given that the downstream over-current protection could be provided by 2 x 13A fuses, and given that very few of the general public have any reason to believe that they should not plug in 2 x 13A loads, I personally think it would be questionable to regard the design current as anything less than 26A.

Firstly, if you think that very few of the general public have any reason to believe that they should not plug in 2 x 13A loads, then how would it not be questionable to install any DSOs, knowing as you do that if someone uses them for 2x13A loads they could seriously overheat?

Secondly, how can you ever determine the Ib of any socket circuit, irrespective of what its In & Iz are?

Thirdly, how can you ensure that you comply with the part of 433.1.204 which you represented with an ellipsis if your take on Ib is that it is 13x the number of plugs which can be inserted?

 

[ban-all-sheds]

If I have understood correctly, this is the configuration:

View attachment 85949

Not sure what that is supposed to be. But if you remove the top ring in my drawing you end up with this:

which is not a ring final as per the definition in Part 2.

 

[EFLImpudence]

Obviously I may be wrong, but:

I've recently moved to a house that seems to have a separate ring downstairs in an extension that is joined to the upstairs ring. It doesn't seem to be extended as typical ie breaking the loops and inserting more sockets, rather it is a separate ring but joined to the upstairs ring at two places (sockets). So two sockets upstairs have been chosen with 3 cables each and two in the extension with 3 cables each. IYSWIM

 

[JohnW2]

[amidst another serious abomination of quoting ]It is easy to read it that way, and I do disagree that " the cable " means the spur one(s). It's worth noting that the problems you see with spur cables not having explicit prescriptions within 433.1 ....

I didn't, at least until now, "see any problems" because my interpretation was that spur cables were implicitly included (as cables which were part of 'the circuit') in 433.1.204.

Firstly, if you think that very few of the general public have any reason to believe that they should not plug in 2 x 13A loads ...

Do you disagree that such is the case?

... then how would it not be questionable to install any DSOs, knowing as you do that if someone uses them for 2x13A loads they could seriously overheat?

I think it is theoretically questionable. IMO, even more questionable (given what I believe to be the general public's belief) is that it is 'allowed' to sell sockets with 2 x 13A outlets that cannot safely deliver 2 x 13A. However, this is drifting off the matter under discussion.

Secondly, how can you ever determine the Ib of any socket circuit, irrespective of what its In & Iz are?

In general, one can't. As I'm always saying, proper design of multi-socket circuits is impossible, since the designer has no control over, and no certain knowledge about, what may be plugged in - which theoretically could be an enormous load if there are many socket outlets. However, when it's just one double socket that one is talking about, one can/could assume the worst-case scenario of 2 x 13A loads being plugged in, without the need for any of the guesswork (or invocation of crystal balls) required when there are multiple sockets.

Thirdly, how can you ensure that you comply with the part of 433.1.204 which you represented with an ellipsis if your take on Ib is that it is 13x the number of plugs which can be inserted?

See above.

Kind Regards, John

 

[JohnW2]

Obviously I may be wrong, but:

I've recently moved to a house that seems to have a separate ring downstairs in an extension that is joined to the upstairs ring. It doesn't seem to be extended as typical ie breaking the loops and inserting more sockets, rather it is a separate ring but joined to the upstairs ring at two places (sockets). So two sockets upstairs have been chosen with 3 cables each and two in the extension with 3 cables each. IYSWIM

I still think it's pretty ambiguous, and that either of our interpretations could be correct.

Kind Regards, John

 

[scousespark]

You appear to have the lowest opinion of electricians that I have come across.

That's simply not true. As in all walks of life, I'm sure that there are some 'bad' electricians', and some 'exceptionally good' electricians, with the vast majority being somewhere in-between - but that's not what I was talking about. I was referring to the fact that a lot of electricians will not have been trained to test, and will have little, if any, experience of testing, circuits of the type we were discussing, and that not all of them will inevitably find it easy to work out for themselves how that testing should be done.

If an electrician has been trained to BS7671 they will know what to expect when they find an interconnection in a ring final cicuit.

To the extent you have stated that yourself, and a select few other atypical diyers, should be regarded as equal to trained/qualified/experienced electricians - despite having no training, qualifications or provable experience.

If you believe that I have stated or claimed that, either I expressed myself very badly or you misunderstood. As you say, I have no training or qualifications, and little experience. What may be true is that I, and a few other non-electricians, have an understanding of the principles involved (and 'the regulations') which is comparable with that of many electricians - but that in no way makes me "equal to" a trained, qualified and experienced electrician.

I was referring to a post were you stated you would prefer a change to Part P to allow registered electricians and atypical diyers to self certify their jobs.

Are you now seriously saying you believe the people behind the regs omit things because mere electricians would not be able to undertand what was written?

I am saying that I could understand "the people behind the regs" being hesitant to 'promote' a type of circuit which required appreciably more complex testing than most electricians have been taught to undertake, or have been called upon to undertake. However, that is pure speculation, and there are countless other reasons why they might no want to 'promote' such a circuit - particularly given that they are probably under some pressure to disallow ring circuits of any type.

As I said, this is not some amazing design by a super electrician - it's a ring with an interconnection. As such it doesn't require a phd in physics to undersstand the readings on the test meter.

Some of us actaully know what the numbers on our test equipment represent and can even (I know you won't believe this) understand what is happening in the circuit we are testing. Of course, as you have NEVER met an electrician with anywhere near your grasp of all things electrical, you won't believe a word of this.

Sarcasm is not necessary, and will not help your argument. Of course I accept that many electricians have a very good understanding of what their test results mean and "what is happening" in the circuit concerned.

You frequently tell us about the electricians you come into contact with and how little they understand about the principles of electrical theory. I have never seen you post that you have met one who has demonstrated this understanding.

If I came across this circuit in a test, I'd note it but not code it.

That seems very reasonable, but I presume that is not all that you would do. Detecting the presence of a cross-link is the start, but, having detected it, I presume that you would then take the necessary steps to confirm that there was satisfactory continuity (of L, N and CPC) within each of the 'sub-rings' - since, if any such continuity was absent/unsatisfactory, I imagine that you probably would feel the need to 'code' it. That additional testing obviously can be done, although it is appreciably more complex than the testing that most electricians are used to, but it probably is not often taught, and does not appear in, for example, GN3.

I didn't think I needed to specify that this only applies when the tests are all passed.

As I said, this whole discussion started because a significant proportion of electricians appear to believe that a cross-connection in a ring is non-compliant - and therefore should, in itself, be 'coded'. Did it? Reading back, it was you who decided that thius is beyond the wit of most (or at least a large majority of) electricians.

If I was asked to work on it, I'd only do so after removing the interconnection. If you would do differently, then that's fine.

I would probably do the same, just as I would never deliberately install such a circuit in the first place - primarily because I don't want to make life more difficult/confusing than it need be for anyone who may work on the circuit in the future.

In my post I did say this would be an example of good practice.

Kind Regards, John