Why are ring finals split up/down not side/side?

[DetlefSchmitz]

I'm not so sure about that - the more pins there are, the less pressure each one applies to the skin, so the less likelihood is there of skin penetration

This is all very hypothetical. I think you owe it to us to try putting your full weight on each DIL IC type in turn , and let us know which hurt the worst.
Full disclosure: It was my wife who stepped on my 14 pin DIL. Not me.

 

[JohnW2]

Ignoring the historical reasons as to why the UK developed the ring circuit, has anyone any doubt that the UK system is by far the best system in the world?

Quite a lot of people, even in the UK, have at least 'lots of doubts' about ring finals, with a good few feeling that they 'should not be allowed, with some believing that the day will come when they are not 'allowed'). Unless yopu want to just be arrogant on behalf of the UK, one also has to at least wonder why, if they were such a good idea, virtually no country without historical affiliations to the UK (many of which are 'technologically sophisticated') has ever implemented ring finals (in the UK sense).

As I've been trying to say, it's really the fused plug (not the ring final circuit) which I personally regard as a pretty clever and useful idea (which is pretty exclusive to 'anglophile' countries).

If one is starting from scratch, with many arrangements of sockets, a 4mm² 32A radial will 'use no more (quite often less) copper' than would a 2.5mm² ring final. Either circuit allows an 'unlimited' number of sockets but, in the case of the radial, without the 'assumptions' (reasonable though they seem to be) intrinsic in a ring final - but, in either case, one needs the fused plugs. Indeed, in situations of high potential demand, there's no reason why one could not have, say, a 6mm² 40A or 45A radial - in which case the fused plugs would be even more essential.

Given that there will usually be little or no 'copper saving' resulting from using a ring, rather than a radial, as far as I can see the only thing really to be said for ring finals is that they provide CPC redundancy. The main downside of ring finals (which is one of the main reasons why some people think that they 'should not be allowed' is that a break in the L or N ring will go totally un-noticed by the user, but could result in appreciable overloading of cable.

So, to respond reiterate in response to your question, I personally believe that the use of fused plugs is a pretty clever/useful idea, but I see no real reason for ring finals (which is perhaps the considered opinion of 'the rest of the world').

Kind Regards, John

 

[JohnW2]

This is all very hypothetical. I think you owe it to us to try putting your full weight on each DIL IC type in turn , and let us know which hurt the worst. Full disclosure: It was my wife who stepped on my 14 pin DIL. Not me.

As I've just written (per my edit, which preceded your comment by a good while), it's not 'hypothetical' - it's the principle which makes the 'bed of nails' work (with no penetration and little, if any, real pain). However, as I also wrote, one has to be very careful not to put one's whole weight on a small number of pins/nails/whatever (let alone your suggestion of putting all one's weight on just one of them!) - since that will hurt, and probably cause skin damage!

Kind Regards, John

 

[DetlefSchmitz]

We were actually not talking about beds of nails, but whether accidentally putting your weight with one foot onto a 14 or a forty pin ic hurts more. It is my belief that even with 40 pins they will penetrate your foot and therefore hurt about 2.857 times as much as a 14 pin one. To prove otherwise, it behoves you to try it. I also clearly said one IC type. Not one IC pin.

MOD: Amusing as this thread is, it has strayed somewhat off topic.

 

[SUNRAY]

The early ring circuit, pre-decimalisation was usually wired in 7/0.29

Or 3/0.044

I'm not sure that I understand that. One could 'double the capacity' by simply adding a second 15A radial (without creating a ring), with essentially the same cable/copper implications as with what you suggest, couldn't one?
Kind Regards, John

Interestingly I'm going through a conundrum at the moment in a village hall.
The arrangement for stage lighting was 3x16A radial (approx 27m of 2.5mm²) feeding a 13A SSSO each.Typically each would have a 13A 4way added to supply the various dimmer packs etc. Once I became involved I fairly quickly added some more SSSO's to do away with the 4ways and later added a 4th 16A radial.

Practicalities: Each 4 channel dimmer pack will typically power upto 4 lamps of 500W or 650W. Working with the 650W's it gives about 11A per pack and the current scheme is to use 2 packs on a 16A radial but plan the lighting scenes such that never more than 6 of the possible 8 lamps are in use (far too easy to get wrong and trip a breaker!) OR limit it to 1.5 packs (6 lamps) per circuit.
The conundrum is: Do I convert the 4 radials into 2 ring finals, in which case I can fill 3 packs with 12 lamps with impunity twice?

 

[EFLImpudence]

As you have used 2.5mm², why have you used 16A MCBs?

 

[JohnW2]

As you have used 2.5mm², why have you used 16A MCBs?

You beat me too it (again!).

The issue here seems to be nothing to do with the type of circuit, but rather its 'capacity' of each one (i.e. its OPD) - which is currently about 1.5 times each of his 'loads' (hence very 'inconvenient'). If the 2.5mm² is Method C, then 25A MCBs (if available) would allow each of the circuits to service 2 x 11A loads (and 20A MCBs "wouldn't be far off" -{and would never trip with 22A}!).

Kind Regards, John

 

[SUNRAY]

The issue here seems to be nothing to do with the type of circuit, but rather its 'capacity' of each one (i.e. its OPD) - which is currently about 1.5 times each of his 'loads' (hence very 'inconvenient'). If the 2.5mm² is Method C, then 25A MCBs (if available) would allow each of the circuits to service 2 x 11A loads (and 20A MCBs "wouldn't be far off" -{and would never trip with 22A}!).

Kind Regards, John

An excellent summary of the situation, Personally I'd prefer to not go down the ring route for all the reasons mentioned on this site added to the potential mistreatment that happens in public buildings.
My first suggestion was increasing the MCB's to 20A and i'd have been delighted with that but the calcs don't permit it. Sadly the cable route includes a heavily insulated and sometimes very hot ceiling void and insulated stud wall, the circuit was designed, tested and signed off by the Halls 'aproved electrician' which we, the drama group, have to go through this route.

Bearing in mind the mix of 500W & 650W lamps the load could just as easily be 2KW and I do try to take this into account whilst rigging.

 

[JohnW2]

An excellent summary of the situation, Personally I'd prefer to not go down the ring route for all the reasons mentioned on this site added to the potential mistreatment that happens in public buildings.

Indeed.

My first suggestion was increasing the MCB's to 20A and i'd have been delighted with that but the calcs don't permit it. Sadly the cable route includes a heavily insulated and sometimes very hot ceiling void and insulated stud wall, the circuit was designed, tested and signed off by the Halls 'aproved electrician' which we, the drama group, have to go through this route.

Hmmm. If the installation method of the cable is such that it cannot support a 20A MCB, and given that you are 'playing by the rules', your options would seem to be very limited....

... The 'conundrum' you posed (whether or not to convert the 4 radials into two ring finals) now becomes easy to solve/answer, since conversion to rings would not be BS7671-compliant, given that 433.1.204 requires that the cable of a ring final must have a CCC of at least 20A.

If the installation method is such that 2.5mm² cable has a CCC less than 20A, then (even if you were prepared for the amount of work/disruption) even upgrading the cables of the radials to 4mm² (with same route) would presumably not be enough to allow a 32A MCB. Running an additional 2.5mm² cable in parallel with the existing one (hence 5mm² total), might be enough, but one would need to do the sums.

Kind Regards, John

 

[securespark]

The early ring circuit, pre-decimalisation was usually wired in 7/0.29

Whatever it was wired in 15A fuse required at least 20.7A cable - and 30A, 41.4A cable.

7/0.29, clipped direct would carry 25A.

 

[EFLImpudence]

7/0.29, clipped direct would carry 25A.

What are you saying? Was I getting confused by rings and radials?

The chart I posted states 20A for 7/0,29, but even 25A would not be quite enough for a 30A ring.

 

[securespark]

Sorry, posted this without reading your post.

Dunno why my book says 25 for clipped direct and yours says 20?

 

[EFLImpudence]

No problem.

I don't know which is correct, then.

 

[JohnW2]

Dunno why my book says 25 for clipped direct and yours says 20?

Might this perhaps again be a matter of the what OPD (particularly what 'fusing factor') the Tables relate to?

Although we call the figures in these tables 'Current Ratings', they necessarily assume protection by an OPD with a certain 'fusing factor'. In other words, when we look at the current Tables and find that a cable of a certain CSA has a 'current rating' of, say, 20A, that assumes an MCB and therefore means that the cable is deemed to be able to carry 29A (20A x 1.45) for at least an hour without coming to harm.

A corresponding Table which assumed a BS3036 fuse would presumably give the CCC for the same cable as 14.5A - again indicating that it could carry 29A (but this time 14.5A x 2) for at least two hours.

Kind Regards, John

 

[SimonH2]

Why, then, did only Britain think it necessary to have 30A socket circuits in domestic properties, the vast majority of which were very small?

Wasn't this around the time of nationwide electrification and building of the national grid ?
Having watched documentaries about this, ISTR that there was a big thing of the bright new future with lots of electrical stuff. As has been pointed out, by the 60s (where my memories start) it was common for those houses still with "a single 15A per room, if that" tended to have a tree of adapters (including unfused adapters down to 5A sockets). If people were going to have electric heaters, electric washing machines, electric this that and the other, then they'd need more than one 15A socket. Just multiple 15A sockets on one 15A radial wasn't going to cut it when faced with several multi-kW devices plugged in. So that could mean multiple 15A radials, or multiple sockets on one higher current circuit and taking advantage of demand diversity to plug in more devices than just adding their loads would suggest the circuit could support.