Spur - socket and Fused Spur from Ring?
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I presume that you are referring to the guidance in Appendix 15 - but, as I'm sure you are aware, that guidance does not constitute 'a regulation' and nor is compliance with that guidance necessarily required for 'compliance with the regs'.
Kind Regards, John
Thanks - I lost track of this being another aspect of circuit arrangements changed from specific regulations to just guidance.
I'm struggling to see the way BS7671 is heading these days.
Since when does one need permission to install a floodlight?
It has moved away from straightforward instruction to more a set of rules of what must be achieved for safety.
Unfortunately, this involves thinking.
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Whilst there is a lot to be said for allowing discretion regarding details (provided those implementing the regs have the knowledge, ability and inclination to do that), it does seem (at least to me) rather odd for a Standard.
Since the Building regs imposed a 'recommended maximum' on the size/power of external lighting.
Kind Regards, John
Rather odd? That's exactly what Standards are supposed to do, i.e., set objectives to be achieved. They are not textbooks!
No other class of person should be doing it, and the regulations should not be dumbed down to cater for the limited abilities of people who are insufficiently competent.
There is NOTHING different about the design of a spur from the design of any other circuit where overload protection is not required because of the nature of the load. Of course there are other considerations due to it being a load on the ring, but the actual spur itself is just a cable with a load and a protective device, and if someone does not understand that then they should not be doing circuit design work.
By way of approved document for Part L?
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How far do you want to take that? I propose a greatly simplified next edition of BS7671. Here's the full text:
Regulation 1. The electrical installation in a building shall be designed and installed in such a manner as to provide a reasonable degree of safety against the risks of fire and electric shock.
That should be enough, surely? Anyone who is sufficiently competent shouldn't need anything further.
Obviously I'm being more than a little facetious, but how far do you want to go with this? Does somebody who is competent need a regulation telling him that a switch intended to isolate some device to make it safe for maintenance needs to open the live conductors, for example? Does he need a regulation telling him that a conductor should be protected by a suitable fuse or circuit breaker?
That may be true of some types of Standards, or some aspects of Standards, but many of them are surely necessarily very prescriptive at the level of detail. Think of screw threads!
Kind Regards, John
Yes, it's the Approved Document which actually gives recommended figures, but Part L itself requires that there be reasonable provision for the conservation of power - and a 400W floodlight in domestic property might well be considered not to constitute such reasonable provision.
Kind Regards, John
In some senses you're right, but that is not the nature of rules, regulations and legislation. Apart from anything else, in the absence of detail, any accusation of failure to comply with a 'bottom line' regulation such as you suggest (which is very similar to Part P) becomes a matter of opinions.
In many fields in which rules, regulations and laws have to be complied with by highly intelligent, highly educated and highly regulated professionals, much of what those rules etc. say are complete insults to the intelligence of those who have to comply, but that doesn't stop such things being written in the 'rulebooks'.
Kind Regards, John
The point is that the regulations already contain everything one needs to know to create a spur from an RF which complies with the regulations.
Up to a point, although you have admitted yourself that there is also the question of the impact on the ring. One could, for example, design a 4mm² spur supplying umpteen sockets which would, in itself, be compliant with the other regulations, but whether it would be wise or reasonable to connect it to a ring final, with its particular peculiarities, (particularly if connected close to one of its ends) is a different matter. ... and no regulation gives any explicit help in deciding whether it would be 'wise or reasonable'.
Kind Regards, John
John - please recall that the context of all this is:
And the loading of the ring has precious little to do with spurs, as one could fit 2 DSOs right next to each other.
Nothing to do with the loading of the ring.
And the loading of the ring has precious little to do with spurs, as one could fit 2 DSOs right next to each other.
Yes, I realise that, but you appeared to be making statements which were more general than that specific context.
Indeed - or a row of 5 of them side-by-side. This is another aspect of ring final design about which the regs contain no explicit rules, or even give explicit guidance. The same electrical considerations apply in those cases as with a 4mm² multi-socket spur.
Kind Regards, John
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