Ring Final Circuits (OK I don`t think that Flameport likes them!)

[ebee]

Agreed, I know you wouldn`t usually do these odd circuits in real life (well I hope most of us wouldn`t anyway!) but I often come across people who says that this is wrong/dangerous/unsafe for a variety of reasons. One big "reason" goes something like "It`s not in the On Site Guide so it is wrong/not allowed" etc.
A great man said something like - the OSG is a recipe book it is not a Bible, BS7671 is the Bible (in so far as we are concerned). Similarly if it`s not in Whitfield`s Guide or Part P Approved Doc much the same applies.
We see something odd/strange/unusual and we think what? then some dream up reasons to damn it quite illogically . Quite simply we can use skill and engineering judgement and create a safe system with regs and calcs or we can more easily do something safe and compliant using the guides. How often do you hear someone say "It has fuses not breakers so it`s probably illegal" ?
Unusual solutions look odd in the first instance, course they do but that does not, in itself, make them unsound.

Nobody actually condemned any of those circuits I mentioned, on another day then I expect one or two might do

 

[ebee]

Shall we discuss "Lollipop Circuits" now? One remark I heard a few years back was that a 6.0 T & E had a 2.5 cpc yet the ring portion had 2 x 1.5 cpcs therefore 3.0 equivalent therefore such a reduction could be dangerous.

Only a couple of times in my working life have I converted an obsolete cooker circuit to a lollipop circuit because in those particular circumstances they were the most optimal solution

 

[JohnW2]

Agreed, I know you wouldn`t usually do these odd circuits in real life (well I hope most of us wouldn`t anyway!) but I often come across people who says that this is wrong/dangerous/unsafe for a variety of reasons. One big "reason" goes something like "It`s not in the On Site Guide so it is wrong/not allowed" etc.

Agreed.

A great man said something like - the OSG is a recipe book it is not a Bible, BS7671 is the Bible (in so far as we are concerned). Similarly if it`s not in Whitfield`s Guide or Part P Approved Doc much the same applies.

Again agreed. I don't think there is much, if anything, actually 'wrong' with either the OSG or the Approved Documents ('P' or any of the others), even though their 'guidance' often goes beyond what is actually necessary to satisfy regulations. Given the world as it is they probably serve a useful purpose, since for a person unable or unwilling to think for themselves (on the basic of an understanding of the principles and the actual regulations), following the guidance of such cookbooks will usually result in their work being fairly safe. It is, of course, a pity (albeit a fact) that such people exist.

We see something odd/strange/unusual and we think what? then some dream up reasons to damn it quite illogically . Quite simply we can use skill and engineering judgement and create a safe system with regs and calcs or we can more easily do something safe and compliant using the guides. How often do you hear someone say "It has fuses not breakers so it`s probably illegal" ? Unusual solutions look odd in the first instance, course they do but that does not, in itself, make them unsound.

As above, I essentially agree. I suppose that one thing to be said against the unusual/unconventional (but satisfactory in terms of both electrical considerations and regs) is that they may cause 'problems' for people (as above) unable or uninclined to think for themselves (when working on the installation, let alone fault-finding or 'testing' it) - although, again as above, it's a pity that such people exist (but they do). However, even for the person who is very competent and knowledgeable, and able to think, working, fault-finding or testing of 'unusual' installations will usually take them at least a bit more time that would be the case if everything were 'conventional'.

Nobody actually condemned any of those circuits I mentioned, on another day then I expect one or two might do

There's still time!

As your title implies, there are some who are not particularly happy with ring final circuits at all, but I doubt that the sensible ones of even those people would suggest that they were 'unacceptable' or 'potentially dangerous'.

Kind Regards, John

 

[JohnW2]

Shall we discuss "Lollipop Circuits" now?

There's clearly nothing wrong (electrically) with a (correctly designed) 'lollipop circuit', even if it is not mentioned, or illustrated as an example, in BS7671 or any of the associated documents - and I can see no reason why a correctly designed one would not be fully compliant with regs.

... Only a couple of times in my working life have I converted an obsolete cooker circuit to a lollipop circuit because in those particular circumstances they were the most optimal solution

I have exactly that arrangement in my cellar - an obsolete cooker circuit (I think actually 10mm²), now protected by a 32A MCB, feeding a 2.5mm ring final (and also appropriately 'fused-down' lighting circuits) in my cellar. Nothing wrong with that. In fact, it obviously has a lower Zs, and less VD, than would be the case if the ring were wired all the way back to the CU in 2.5mm² cable.

One remark I heard a few years back was that a 6.0 T & E had a 2.5 cpc yet the ring portion had 2 x 1.5 cpcs therefore 3.0 equivalent therefore such a reduction could be dangerous.

I mentioned people who think(or don't!) or talk like that in my previous post

What I did once see, and which clearly was wrong (and, at least theoretically, 'potentially dangerous') was the creation of a lollipop circuit by feeding a 2.5mm² ring from a re-purposed obsolete 10mm shower circuit, but leaving it with a 40A or 45A MCB. Again, a lack of understanding, thought, or ability to think!

Kind Regards, John

 

[SUNRAY]

What I did once see, and which clearly was wrong (and, at least theoretically, 'potentially dangerous') was the creation of a lollipop circuit by feeding a 2.5mm² ring from a re-purposed obsolete 10mm shower circuit, but leaving it with a 40A or 45A MCB. Again, a lack of understanding, thought, or ability to think!

Kind Regards, John

I found a pair of rings sitting on the end of a heavy cable, I think bigger than 10mm² on green Wylex 45A fuse. On site electrician was going on about 2.5mm² being capable of 25A so nothing wrong with it...

 

[JohnW2]

I found a pair of rings sitting on the end of a heavy cable, I think bigger than 10mm² on green Wylex 45A fuse. On site electrician was going on about 2.5mm² being capable of 25A so nothing wrong with it...

Hmmm. I can but repeat what I recently wrote to ebee in response to one of his anecdotes, namely ..

I mentioned people who think(or don't!) or talk like that in my previous post

Kind Regards, John

 

[EFLImpudence]

(... and possibly re: the above)

A bog standard ring final circuit with a 30A amp rewireable fuse or 30A or 32A MCB at the fuseway:-

That is the problem with ring finals today which makes them a pointless anachronism.

What I mean is that the regulation 433.1.204 is still written for a BS3036 30A fuse and its CCC derating requirements.
Edited after only Securespark noticed my mistake.

When today using a 32A MCB the regulation still stipulates the ring conductor, if T&E, must have a minimum CSA of 2.5mm² while also stating that that conductor may have a minimum CCC of 20A having just prohibited the use of such a conductor. So, with a 32A MCB and the conditions of a ring circuit, 1.5mm² T&E could be used - or conversely, with 2.5mm² T&E, a 40A MCB. Perhaps more of an actual advantage over a 25A radial.

As things stand with these over-restrictions, the benefit of a ring circuit is falsely reduced compared with how things were when they were introduced.

The only advantage being the installation of the cables in some thermal insulation without thinking - but that would apply to any circuit if the regulations stipulated that the next size larger cable must be used.

 

[Murdochcat]

The only time I would install RFC these days would be for a kitchen

Everything else radials all the way

 

[SUNRAY]

The only time I would install RFC these days would be for a kitchen

Everything else radials all the way

I know we all have our opinions but personally I see no point in spending extra money and adding to the difficulties with thicker cable or adding more circuits.

 

[Murdochcat]

I know we all have our opinions but personally I see no point in spending extra money and adding to the difficulties with thicker cable or adding more circuits.

who said anything about thicker cables ?

more circuits is the most sensible split in a home to minimise inconvenience (314.1.2 iirc)

 

[JohnW2]

who said anything about thicker cables ?

SUNRAY did, as an alternative to:

more circuits is the most sensible split in a home to minimise inconvenience (314.1.2 iirc)

I don't know what experiences lead people to have concerns about such things but,, as far as I am concerned my 'inconvenience' has already been well 'minimised', since the number of occasions on which I have lost any circuit in my house in the last 50 years has been negligible, and the number of times I've lost a circuit for an appreciable period of time almost zero.

... and, as I often say, if your idea of 'more circuits with thinner cables' means 20A radials, I'm personally far from keen on that idea, particularly in kitchens - but that's just me!

Kind Regards, John

 

[Murdochcat]

SUNRAY did, as an alternative to:

I don't know what experiences lead people to have concerns about such things but,, as far as I am concerned my 'inconvenience' has already been well 'minimised', since the number of occasions on which I have lost any circuit in my house in the last 50 years has been negligible, and the number of times I've lost a circuit for an appreciable period of time almost zero.

... and, as I often say, if your idea of 'more circuits with thinner cables' means 20A radials, I'm personally far from keen on that idea, particularly in kitchens - but that's just me!

Kind Regards, John

Best you read my comment again

 

[JohnW2]

Best you read my comment again

What, the bit that says that you would install a Ring final circuit ("RFC" could also be a Radial Final Circuit ) in a kitchen ? If so, yes, I read that, but there's no particular reason for needing for a ring - it could be a 4mm² 32A radial - and, despite the fact that you call it 'thicker', I personally find 4mm² T+E much nicer to work with than 2.5mm²,so I'm not sure what issue you may have with it.

As those who have been regulars here for some time will know, I'm pretty 'neutral' as regards the ring vs. radial debate - but I do find it a bit odd that some people come very strongly, sometimes passionately' into one or other of the two camps! These days, there seems to be little point in having rings, but also no strong reason for not having them.

Kind Regards, John

 

[SUNRAY]

who said anything about thicker cables ?

more circuits is the most sensible split in a home to minimise inconvenience (314.1.2 iirc)

The expense of fitting a number of 16/20A 2.5mm² or 32A 4 or 6mm² radials (other than for a specific purpose) is in my opinion crazy.


Like john my failures here since 1994 are minimal, the biggest outage being rodent damage to a lighting circuit in the loft which required replacing 2 pieces of cable. Actually they were only twin so I took the opportunity to upgrade to T&E and the whole job including fault finding, doing away with a borrowed neutral and moving one circuit in the CU was under 4 hours. It all happened while Mrs Sunray was at work for a half day and apart from detecting some detritus which I had missed while cleaning up afterwards would have known nothing of the failure.

The only other trouble being the dishwasher interference suppressor very intermittently tripping one of the split board RCDs overnight which resulted in a failry drawn out several weeks of fault-finding (not detectable with insulation tester) and replacing with RCBOs The biggest inconvenience being setting the VCRs and other clocks.

In all the failure cases (again very minimal) there has been a distinct cause but downtime is not worthy of mention.

 

[SUNRAY]

What, the bit that says that you would install a Ring final circuit ("RFC" could also be a Radial Final Circuit ) in a kitchen ? If so, yes, I read that, but there's no particular reason for needing for a ring - it could be a 4mm² 32A radial - and, despite the fact that you call it 'thicker', I personally find 4mm² T+E much nicer to work with than 2.5mm²,so I'm not sure what issue you may have with it.

As those who have been regulars here for some time will know, I'm pretty 'neutral' as regards the ring vs. radial debate - but I do find it a bit odd that some people come very strongly, sometimes passionately' into one or other of the two camps! These days, there seems to be little point in having rings, but also no strong reason for not having them.

Kind Regards, John

I'm most definitely in your camp John regarding the 2 versions of RFC.
I have both in my home but only because it's what I want, namely fridge/freezer, TV, shower, outside sockets and outbuilding radials.

I Personally think 4mm² and 2.5mm² have pro's and con's and reading some previous comments about 7/0,029" cable I suspect I'm not alone, however I don't think the difference is worthy of concern. One is easier to pull into containment t'other is easier to clip direct for example.