What do you think will be new/changed in the 18th edition?

[JohnW2]

But for many installations, I think you'll find that a 32A radial using 4mm cable uses more copper than a 32A RFC using 2.5mm cable. It does depend on the topology, but in most houses, to "close the ring" doesn't actually need all that much extra cable. Since 4mm cable has 60% more copper than 2.5mm, that means you can add nearly 2/3 of the radial length to complete the ring before you are using more copper in the (2.5mm) RFC than in the (4mm) radial. In most houses, it would be difficult to exceed that with a sensible cable route.

That's all true. However, although it's allegedly the main reason that ring finals came into existence, 'amount of copper used' (or even the cost of it) would not be a significant criteria in my melting pot when I was making a ring/radial decision.

Not to mention, it's hard enough terminating multiple 2.5mm cables in some of the socket/backbox combinations - 4mm can't be easier

I also used to be 'frightened' of 4mm² cable for that reason but, as I've acquired experience, I don't really find it much worse than 2.5mm², in most situations, any more.

Kind Regards, John

 

[SimonH2]

I also used to be 'frightened' of 4mm² cable for that reason but, as I've acquired experience, I don't really find it much worse than 2.5mm², in most situations, any more.

I'm not frightened of it - but I don't really see much point making things harder than they need to be.

Another factor is that without a full rewire, it's not trivial to replace a 2.5mm RFC with a 4mm radial. So a case of "new installations (or full rewire) only".

 

[JohnW2]

Another factor is that without a full rewire, it's not trivial to replace a 2.5mm RFC with a 4mm radial. So a case of "new installations (or full rewire) only".

Very much so. As is probably apparent from what I write (on different occasions presenting the arguments in both directions!) I really am pretty neutral (ambivalent?) as regards the ring/radial debate - and I certainly don't think anyone in their right mind would/should even consider changing an existing 2.5mm² ring to a 4mm² radial unless, for some reason (e.g. a complete re-wire) the circuit was going to have to be completely re-wired even if it remained as a ring. So, as you say, it's really only an issue for new installs or full re-wires.

In the absence of faults (in which case it's sometimes done as a 'temporary fix' - even if it then sometimes stays for years!), nor do I see the point in 'cutting' an existing 2.5mm² ring to produce two 20/25A radials.

Kind Regards, John

 

[eveares]

but they are very cost effective.

I mean it would be cheaper to wire a socket based ring final circuit in 2.5mm T&E vs wire a Radial socket circuit in 4mm T&E.

By cost effective, I mean the cost of 2.5mm T&E compared with 4mm T&E.

 

[ban-all-sheds]

So a case of "new installations (or full rewire) only".

I did say

.. deprecation of ring finals

 

[ban-all-sheds]

Wow, I've some catching up to do

John is averaging 13.75 posts per day, you are doing just under 2.

If he maintains his rate, and you up yours to 67.52 per day, you'll catch him up by the end of the year.

 

[EFLImpudence]

By cost effective, I mean the cost of 2.5mm T&E compared with 4mm T&E.

I note on the Screwfix site (Toolstation don't sell it) that 4mm² is all but the same price as 6mm² so it is apparent that tradition lives on.

 

[JohnW2]

but they are very cost effective.

I mean it would be cheaper to wire a socket based ring final circuit in 2.5mm T&E vs wire a Radial socket circuit in 4mm T&E. ... By cost effective, I mean the cost of 2.5mm T&E compared with 4mm T&E.

Fair enough - but, as has been discussed, it's by no means as simply as that. For a start, as I said before, one can use 2.5mm² (20A or 25A) radials at almost exactly the same cost as an equivalent 2.5mm² ring (quite possibly less cable, if it were routed optimally), yet have appreciably more circuit capacity.

As has been said, it all depends upon the topology of the circuit. In comparing a 32A 2.5mm² ring with a 32A 4mm² radial, the very worst scenario would be for the total cable lengths to be the same in the two cases (the radial following the identical route to the ring, simply not connected to CU at on end). Assuming TLC prices for 100m reels, the difference in price between 2.5mm² and 4mm² T&E is about 26.5p per metre - so around £8 difference for 30m circuit or around £13 difference for a 50m circuit. Given the big picture of the costs of having a circuit installed (particularly if one is paying someone to do it), I find it hard to see that can be regarded as making the ring "very cost-effective". There are certainly pros and cons of rings and radials to be considered, but I really don't think that cable cost is really a significant issue.

Kind Regards, John

 

[JohnW2]

So a case of "new installations (or full rewire) only".

I did say

.. deprecation of ring finals

You did, but I can't see how the regs could really 'deprecate' ring finals (at least in any meaningful way) without making them non-compliant for new installs (and probably also for 'full rewires, although I can see that one causing some debates about interpretation and loopholes!). What did you have in mind?

Kind Regards, John

 

[SimonH2]

... but I can't see how the regs could really 'deprecate' ring finals (at least in any meaningful way) without making them non-compliant for new installs (and probably also for 'full rewires, although I can see that one causing some debates about interpretation and loopholes!).

Which means that at some point, you want an extra socket on an existing RFC and it's no longer compliant. It would also throw up a (C3 I guess) item on an EICR which would be of concern to us landlords who like to have a "clean sheet" (if only for a**e covering with "difficult" tenants).

So that means either splitting the ring to two 20A radials* with the problems that would cause in the kitchen, or rewiring with 4mm cable to allow a 32A radial.

* Noting that I've been having a look, and 25A MCBs aren't that common, 25A RCBOs seem to be exceedingly rare.

 

[JohnW2]

... but I can't see how the regs could really 'deprecate' ring finals (at least in any meaningful way) without making them non-compliant for new installs (and probably also for 'full rewires, although I can see that one causing some debates about interpretation and loopholes!).

Which means that at some point, you want an extra socket on an existing RFC and it's no longer compliant. It would also throw up a (C3 I guess) item on an EICR which would be of concern to us landlords who like to have a "clean sheet" (if only for a**e covering with "difficult" tenants).

Exactly my point. However, I suspect that BAS is right that, even if probably not for many decades (and therefore not of concern to many of us!), the day will probably come when the regs attempt to 'phase out' ring finals (a process which, as I've said, in itself would take many decades), and I can't see how else they could achieve that. Given that rings would remain 'out there' for many decades after they became non-compliant for new installs, one hopes that there might be dispensations built into the regs at that time to avoid all the C3s (or whatever they may then be called!) to which you refer.

Kind Regards, John

 

[EFLImpudence]

I do not see how or why ring finals should be banned.

The fact that they are not used elsewhere is because they are not actually required.
Since the introduction of MCBs they are inefficient with oversized conductors or undersized CPDs.

They should be phased out because 'we' have decided not to use them.

 

[JohnW2]

I do not see how or why ring finals should be banned.

As I've said, the 'how' would certainly be challenging. As for the 'why', I've also commented that they have been around for 60+ years, without any clear indication that this has really resulted in any significant problems, so any 'anti' argument is bound to be weak. However, from 'their' viewpoint, I think that it is otherwise unprecedented to have a circuit which, under some situations of user behaviour/usage, could sometimes result in the cable being overloaded to an extent which would not be allowed for any other type of circuit. We all know that the 'safety margins' are such that this is very unlikely to represent a significant danger/hazard in practice, but it is still probably illogical/inconsistent to allow people to 'rely' on those safety margins for ring finals, but not for any other circuits. If they do, one day, try to start phasing ring finals out of the regs, it will probably be in name of 'tidying'/consistency, rather than for any significant safety-related reason.

They should be phased out because 'we' have decided not to use them.

If that happens, it will happen, but there seems no indication of that happening (to its conclusion) any time soon. Whilst I suppose that some sort of 'phasing out''has already commenced, in that at least some people have moved their favours to radials in recent times, I would think that, even in new installations, ring finals remain by far the most common sockets circuits - isn't that true? I'm not sure about the 'why' of that - could it be simply that (as has been suggested) 2.5mm² cable is fractionally easier to handle, in some situations, than 4mm² - or is it perhaps just habit/tradition?

Kind Regards, John

 

[SimonH2]

Whilst I suppose that some sort of 'phasing out''has already commenced, in that at least some people have moved their favours to radials in recent times, I would think that, even in new installations, ring finals remain by far the most common sockets circuits - isn't that true?

Outside of a few "specials", I don't think I've seen or come across a single instance of a 32A radial. I've come across 16A radials - in both my properties where the garage sockets are really just a "token gesture".

I'm not sure about the 'why' of that - could it be simply that (as has been suggested) 2.5mm² cable is fractionally easier to handle, in some situations, than 4mm² - or is it perhaps just habit/tradition?

"Tradition" - for as long as pretty well most sparkies have been in work, sockets have been 13A on a ring final. One ring in small houses, 2 or more in larger ones. It takes a long time for habit to change - it's only a recent thing that houses even get wired for phones now that wired phones are on their way out and people need network cabling !

As for timescales, I recall when I first heard when 13A plugs/sockets came out - and then mused over how many houses still had 5A & 15A sockets after <a few> decades.
It must also be 2 or 3 decades since I recall reading in the IEE rags about the discussions around a common European socket - it would have to be unfused or our neighbours wouldn't accept it, and then there was the issue of how to adapt existing RFCs to suit. And 20 or 30 years later I see that harmonisation effort got a long way

 

[ban-all-sheds]

You did, but I can't see how the regs could really 'deprecate' ring finals (at least in any meaningful way) without making them non-compliant for new installs (and probably also for 'full rewires, although I can see that one causing some debates about interpretation and loopholes!). What did you have in mind?

Precisely that - no new ones to be installed. Replacement during a rewire counts as new.