Spurs off spurs and the Regulations

[mfarrow]

That wording again I again presume you mean "without the first spur being fused down"? However, as I said, AFAIAA a "spur off an unfused spur" is not non-compliant with any specific regulation - merely the 'guidance' in Appendix 15.

Yes I think we're both talking about the same thing, one accessory only off an unfused spur.

As for it being a regulation, I think you are right, it is not explicitly forbidden. One must therefore look towards NICEIC etc for guidance.

I recall that one was once able to have two single sockets stringed together on a spur, but this was then 'banned'. How did it get banned, if it was not in the regulations? Or were the requirements for spurs more explicit back then?

 

[diyer56]

I always thought this was the case - I seem to remember you were allowed 2 x single or 1 x double as spurs off a ring. It was in an old DIY book which I still have - will have to dig it out.

 

[JohnW2]

That wording again I again presume you mean "without the first spur being fused down"? However, as I said, AFAIAA a "spur off an unfused spur" is not non-compliant with any specific regulation - merely the 'guidance' in Appendix 15.

Yes I think we're both talking about the same thing, one accessory only off an unfused spur. As for it being a regulation, I think you are right, it is not explicitly forbidden. One must therefore look towards NICEIC etc for guidance.

I recall that one was once able to have two single sockets stringed together on a spur, but this was then 'banned'. How did it get banned, if it was not in the regulations? Or were the requirements for spurs more explicit back then?

I think I've heard that before. However, if one 'accepts' (and I don't want to restart that discussion!!) that two single sockets are 'rated' to carry 2 x 13A loads (i.e. 26A total), but a double socket only 20A total, then, given that the regs only require cables with CCC ≥20A in ring final circuits, one can see that allowing 2 single sockets might not be appropriate.

However, as I've said, despite Appendix 15, there is AFAIAA currently no explicit regulation limiting unfused spurs to one socket (single or double), so maybe that was also true with past editions of the regs? As with the situation we're discussing in the thread which spawned this one, I think that common sense is required, and that adding a second, tiny, load to an unfused spur should not be 'forbidden' (even if it were).

Kind Regards, John

 

[securespark]

I always thought this was the case - I seem to remember you were allowed 2 x single or 1 x double as spurs off a ring. It was in an old DIY book which I still have - will have to dig it out.

I recall that one was once able to have two single sockets stringed together on a spur, but this was then 'banned'. How did it get banned, if it was not in the regulations? Or were the requirements for spurs more explicit back then?

It used to be in the 14th. It was removed when the 15th was introduced in 1981.

A.40 For ring final sub-circuits complying with Regulations A.30-33, non-fused spurs shall be connected to the ring at the terminals of socket-outlets or at joint boxes or at the origin of the ring in the distribution board. Non-fused spurs shall have a current rating not less than that of the conductors forming the ring. Not more than two socket-outlets, or one twin socket-outlet, or one stationary appliance, shall be fed from each non-fused spur.

 

[securespark]

If you wonder why old codgers talk about rings and joint boxes rather than ring finals and junction boxes, it's because the old regs used to talk this way!!

 

[JohnW2]

It used to be in the 14th. It was removed when the 15th was introduced in 1981.
A.40 For ring final sub-circuits complying with Regulations A.30-33, non-fused spurs shall be connected to the ring at the terminals of socket-outlets or at joint boxes or at the origin of the ring in the distribution board. Non-fused spurs shall have a current rating not less than that of the conductors forming the ring. Not more than two socket-outlets, or one twin socket-outlet, or one stationary appliance, shall be fed from each non-fused spur.

It's interesting that not only has the 'rule' changed slightly (from two to one single sockets), perhaps for the reason I mentioned above, but that the explicit regulation about this has now totally disappeared from the regs (was in also absent in 15th and 16th?). It would be nice to think that this was to enable more flexibility, judgement and common sense to be applied by properly-trained electricians, but I wouldn't put my money on that!

Kind Regards, John

 

[securespark]

Kind of.

Appendix 5 of 15th Ed. says:

A non-fused spur feeds only one single or one twin socket outlet or one permanently connected equipment.

 

[JohnW2]

Kind of. Appendix 5 of 15th Ed. says:
A non-fused spur feeds only one single or one twin socket outlet or one permanently connected equipment.

Fair enough, but was Appendix 5 of 15th (like Appendix 15 of 17th) perhaps merely 'informative', rather than being 'a regulation'? ... and do I take it that (as per current regs) there was no mention of this in any explicit regulation?

Whatever, as you've said, it was clearly when 15th came into force that mention of two single sockets on an unfused spur disappeared.

There are clearly two issues about 'spurs from unfused spurs'. Firstly, as I've already mentioned, there's a question of the CCC of the cable. Since 2.5mm² cable is not, per se, adequately protected against overload by a 30/32A OPD, one has to be reliant on the load (and/or fuses in the load/plugs) to protect the cable against overload. Appendix 15 could, but doesn't (probably because of the second issue, below), mention a 4mm² unfused spur (with unlimited sockets). The second issue is excessive point loading of the ring final (hence potential overloading of one leg of the ring), and they presumably wanted to limit that to a maximum of 20A (one double socket). However, that's far from foolproof, since if the spur arose at a double socket, which itself could be loaded with 20A, that would be a load of 40A at one point on the ring!

Kidn Regards, John

 

[securespark]

Kidn Regards, John

Yuor singnature's gnoe all wrong.

 

[ericmark]

It is interesting to see the old regulations again I had forgotten you were allowed two singles. As to the appendix it is part of the test when taking C&G2382 so one assumes it is part of the regulations.

434.2.1 and the 3 meter rules is also argued about as in essence when you fit a spur on a 32A protected supply one is relying on the fuse in the plug to stop the cable being overloaded so if we consider the appendix as informative help pages then any 2.5 mm² spur protected by a 32A fuse/MCB/RCBO will be limited to 3 meters.

I would personally call a fused spur a radial and class it as a circuit but Part P it would seem considers that ring final is the circuit.

I think the terms ring final is confusing.

I have often wondered if instead of a single 32A MCB we used two 16A MCB's would this make it safer? It is an antiquated system and with the building restrictions today with 1/3 rule not convinced it still has a place the 13A socket great but the ring not so sure.

The problem is with a 20 amp radial we can spur off as many times as we want with out breaking any rules and to tell the DIY guy you can't have a unfused spur from an unfused spur is wrong.

What we are saying is you can't take a 32A supply using 2.5mm² cable unless it feeds a single fused device. As to feeding a array of devices using 4mm² cable I do not really know the answer!

If we have a 4mm² radial from a 32A protective device the any additions using 4mm² cables are just radials and clearly permitted. However where it is a 2.5mm² ring is there anything stopping us from spurring from that with 4mm² to an array of devices? Personally I would say no you can't as it could overload one side of the ring but what about a so called kitchen ring where two 2.5mm² cables feed a grid switch. Is it a ring or conductors in parallel?

The real point is we are trying to simply a complex system for the DIY guy and this can't really be done. So on a DIY forum should we simply say you can't spur from a spur?

 

[EFLImpudence]

But there is a difference between an unfused spur feeding several sockets and feeding several low demand appliances such as a shaver socket, heated radiator and some lights.

As for overloading one leg of the ring, extending the ring 'properly' with several sockets close together may still overload the leg.

It is up to the designer to ensure it is safe however it is done.


A spur does not necessarily have to have a fuse if the load cannot cause overload.

 

[JohnW2]

Kidn Regards, John

Yuor singnature's gnoe all wrong.

You should be very familiar by now with the 'adjacent character transpositions' that result from my high-speed two-finger typing I detect and correct a lot of them, but some get through -particularly 'obvioulsy', which I do so often that it's almost starting to 'look right' to me!

Kind Regards,Jophn

 

[JohnW2]

But there is a difference between an unfused spur feeding several sockets and feeding several low demand appliances such as a shaver socket, heated radiator and some lights.

Quite so, and that's how all this started, with my comment about the shaver socket.

As for overloading one leg of the ring, extending the ring 'properly' with several sockets close together may still overload the leg.

Indeed - but, as I recently wrote, you don't even have to have multiple sockets close together on a ring for that to happen. As I said, just one double socket spured off a double socket (totally compliant) represents a potential load of at least 40A at one point on the ring.

It is up to the designer to ensure it is safe however it is done. ... A spur does not necessarily have to have a fuse if the load cannot cause overload.

Again true (subject to debates about what sort of loads 'can', or 'cannot' cause an overload )

Kind Regards, John

 

[JohnW2]

As to the appendix it is part of the test when taking C&G2382 so one assumes it is part of the regulations.

Assuming you're talking about Appendix 15 etc. of current regs, I don't think you can make that assumption - C&G are free test on anything they wish, whether it is 'a regulation' or not. The current regs are very clear in stating:

"Appendix 1 is normative, and is thus a requirement. All other Appendice sare informative, and are provided as guidance".

It therefore follows that nothing said in Appendix 15 is 'a requirement' of the regs.

Kind Regards, John

 

[JohnW2]

The problem is with a 20 amp radial we can spur off as many times as we want with out breaking any rules and to tell the DIY guy you can't have a unfused spur from an unfused spur is wrong.

We need to tell him/her that (per Appendix 15) they can't have a fused spur from an unfused spur as well. However, because of what you say, we should perhaps be clearer in what we tell a DIYer - namely that all this talk about 'spurs from spurs' relates specifically to spurs from a 30/32A ring final circuit.

Kind Regards, John