two ring mains joined

[JohnW2]

That's only for BS196.

Ah, thanks - I missed that, and also missed A.40!

Kind Regards, John

 

[PBC_1966]

Thanks for the scan; I'll retrieve my two copies of 14th (original & metric revision) one day when the boxes all get unpacked!

A37 is interesting....

uncut ring conductors at every socket!

Why is it repeated verbatim in A53?

Because A.37 is talking about domestic ring final circuits and A.53 is in the section for non-domestic using BS196 connectors.

And is A58 asking for DP switches on lighting circuits?

No, only for heating appliances in which the element can be touched when switched off.

 

[JohnW2]

Because A.37 is talking about domestic ring final circuits and A.53 is in the section for non-domestic using BS196 connectors.

It seems that the 'domestic' and 'non-domestic' sections were not very clearly demarcated - hence my recent mistake!

Kind Regards, John

 

[securespark]

Doh! And mine too...despite knowing about the existence of the two different circuits.... where's my jacket?

 

[scousespark]

This is not an example of some totally brilliant 'electrician' installing a circuit which is causing issue because 'BS761-trained cable installers' don't know what to do with it. It is a standard ring final with an interconnection. There are 2 elements to he job - the first is the regulatory framework and the second is best practice. I follow the KISS principle (Keep It Simple Stupid) and this design gives no advantage over a standard ring. I do not know any electrician/BS7671-trained cable installer who would install the described circuit.

 

[securespark]

My guess is that the downstairs was intended to be an extension of the first floor ring final but it went horribly wrong when they did not know how to break into the circuit.

 

[JohnW2]

This is not an example of some totally brilliant 'electrician' installing a circuit which is causing issue because 'BS761-trained cable installers' don't know what to do with it. It is a standard ring final with an interconnection. There are 2 elements to he job - the first is the regulatory framework and the second is best practice. I follow the KISS principle (Keep It Simple Stupid) and this design gives no advantage over a standard ring. I do not know any electrician/BS7671-trained cable installer who would install the described circuit.

I don't think that many people would disagree with most of that (although, as I've said, I do see some theoretical advantages in cross-connected rings).

So, I don't think that any of us believe that this circuit was deliberately installed in the way that it has ended up. The whole of this started as a discussion about whether such a circuit (even if installed 'unintentionally') should be 'condemned' as 'non-compliant' - and no-one has yet been able to cite a regulation it violates - unless, that is, you accept BAS's argument that, since it is "not a ring", 433.1.204 does not apply. The more technical discussion arose out of that, since I believe that it is, if anything, actually 'safer' than a bog-standard ring (as undeniably allowed by 433.1.204), so I feel cannot, at least in common sense terms, be said to be non-compliant.

started

 

[EFLImpudence]

We are free to design whatever we want as long as it complies with the regulations.
It cannot be expected that the regulations mention and confirm every weird and wonderful installation method even if we would never do it.

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

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.

 

[JohnW2]

We are free to design whatever we want as long as it complies with the regulations. It cannot be expected that the regulations mention and confirm every weird and wonderful installation method even if we would never do it.

Exactly my point.

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

Again, my point. I'm perfectly open to being corrected but, AFAICS, there is no sense in which it is any 'less safe' than a single ring. As I see it, adding any sort of 'cross-connections' to a ring will, at least to some extent, improve current sharing (hence reduce the risk of any of the cable being overloaded for long periods) and reduce both EFLI and VD (as observed anywhere in the circuit), and will provide additional CPC redundancy. The only downside I am aware of is the added difficulty in testing and fault-finding, particularly on the part of those with limited understanding of electrical principles. As I've said, despite the fact that I see 'advantages', I personally wouldn't deliberately install such a circuit, even in my own house, and I doubt that any electricians would - but that's not the point.

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.

Again, I don't disagree with any of that.

As must be apparent, for all the above reasons) I personally would struggle to find a reason why such a circuit was 'non-compliant'. However, if anyone can produce a convincing argument (other than BAS's one about "a ring") for it being non-compliant, I will be very happy to re-consider my view.

Kind Regards, John

 

[securespark]

If the modified standard ring final design of which you talk above is much safer, why don't the IET promote that circuit as the standard ring final design in 7671?

 

[securespark]

Looking through my scan of the 14th, it gives a very precise description of how a ring final circuit should be installed. Is there still a similar description?

 

[PBC_1966]

If the modified standard ring final design of which you talk above is much safer, why don't the IET promote that circuit as the standard ring final design in 7671?

The radial circuit arrangements offer increased safety over the ring (in its present standard form), so why don't they promote those and abandon rings entirely?

 

[JohnW2]

If the modified standard ring final design of which you talk above is much safer, why don't the IET promote that circuit as the standard ring final design in 7671?

I've never suggested that it is 'much safer'. All I've said is that, AFAICS, all of the in-service differences are in the direction of 'safer', rather than 'less safe'.

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. However, probably more to the point, I suspect that IET are probably under constant pressure from certain quarters to 'ban' ring finals, let alone promote variants thereof!

Kind Regards, John

 

[JohnW2]

Looking through my scan of the 14th, it gives a very precise description of how a ring final circuit should be installed. Is there still a similar description?

As I've said, the current regs themselves contain only one very brief paragraph about ring finals (I think unchanged since BS7671:2008 was first published), and that only really talks about what cable/OPD may be used, and what accessories may be supplied.

Kind Regards, John

 

[EFLImpudence]

Looking through my scan of the 14th, it gives a very precise description of how a ring final circuit should be installed. Is there still a similar description?

Does it say 'should'?