15A (15 / 0.725 = 20.7A or even 30A) circuit would
The early ring circuit, pre-decimalisation was usually wired in 7/0.29
15A (15 / 0.725 = 20.7A or even 30A) circuit would
Yes, that is a factor. However, what I was getting at was that (if it were typical), the house in which I spent most of the first couple of decades of my life had just a very small number of (15A) sockets, each on its own dedicated circuit (at least, until 'DSIY' created some branches/spurs ) protected by a 15A (re-wireable) fuse, and the introduction of fused plugs enabled multiple sockets to be supplied by a single circuit, without the flex connected to the plug having to be big enough to be adequately protected by a 30A fuse.... and that 30A rewireable fuse required, because of its fusing factor, "the next size up" from 30A cable (30 / 0.725 = 41.4A) meaning if it were not for the ring introduction the previous existing 15A (15 / 0.725 = 20.7A or even 30A) circuit would have had to be replaced to increase its capacity to 30A. ... So, the fused plug was devised. I don't think the plug design is relevant.
Whatever it was wired in 15A fuse required at least 20.7A cable - and 30A, 41.4A cable.The early ring circuit, pre-decimalisation was usually wired in 7/0.29
Yes, and making it a ring allowed the existing circuit to be uprated to 30Aand the introduction of fused plugs enabled multiple sockets to be supplied by a single circuit, without the flex connected to the plug having to be big enough to be adequately protected by a 30A fuse.
Indeed - but I think we are talking about two different things (and two different ways of 'saving copper') ...Yes, and making it a ring allowed the existing circuit to be uprated to 30A
I am, but the extension and doubling capacity of the 15A radial (rather than replacement) using the existing circuit was, I think, the reason for the ring circuit and it saved copper.... you are talking about the over-current protection of the 'fixed wiring' supplying sockets,
Fair enough. Having done the above then, obviously, the fused plug was required to prevent 'huge' flexes - and had to be different than the 15A unfused plug.but I am talking about the protection of flexible cables connected to the plug.
Chicken and egg, I suppose, depending on where you started. (It was the egg).Even if (by whatever means) one arrived at a situation in which the fixed wiring was adequately protected by a 30A fuse, the flexible cables would (with unfused plugs) also have to be be large enough to be adequately protected by that 30A fuse. This presumably was a disincentive to have circuits rated >15A (and supplying multiple 15A sockets), hence the tendency for one socket per circuit. When fused plugs appeared, this problem went away, so multiple sockets per circuit (hence much less cable/copper) became possible/practical.
I'm a bit confused. Are you suggesting that 30A rings were created by joining together two existing 15A radials? I thought that the 'copper saving'concept of ring finals was introduced primarily (probably almost exclusively) in relation to the massive programme of new builds immediately after the war (in which case all wiring would require 'new copper')?I am, but the extension and doubling capacity of the 15A radial (rather than replacement) using the existing circuit was, I think, the reason for the ring circuit and it saved copper.
Fused plugs (to avoid 'huge flexes') were required because the circuit had been 'uprated' to a 30A one - but that would have been true whether it were a 30A radial or a 30A ring.Fair enough. Having done the above then, obviously, the fused plug was required to prevent 'huge' flexes - and had to be different than the 15A unfused plug.'
I'm a bit confused. Are you suggesting that 30A rings were created by joining together two existing 15A radials? I thought that the 'copper saving'concept of ring finals was introduced primarily (probably almost exclusively) in relation to the massive programme of new builds immediately after the war (in which case all wiring would require 'new copper')?
In as much as it uses very little new cable, joining two existing radials (in an existing property) to make a ring would obviously require a lot less 'new copper' than would putting in new circuit(s), but I'm not sure that I understand why that, alone, would have been done.
I might be wrong but, no. Houses had one socket in each room and few electrical appliances on a 15A circuit.Are you suggesting that 30A rings were created by joining together two existing 15A radials?
I don't really see why that would require the 'invention' of the ring final at all. Two 15A radials would do. They might have decided then to join the two, but why?so I thought that the 'copper saving' concept of ring finals was introduced primarily (probably almost exclusively) in relation to the massive programme of new builds immediately after the war (in which case all wiring would require 'new copper')?
No, there is no point and that is not what I was saying.In as much as it uses very little new cable, joining two existing radials (in an existing property) to make a ring would obviously require a lot less 'new copper' than would putting in new circuit(s), but I'm not sure that I understand why that, alone, would have been done.
Yes I know, but 30A BS3036 radials required the imperial equivalent of 6mm² - a ring, the imperial equivalent of 2.5mm².Fused plugs (to avoid 'huge flexes') were required because the circuit had been 'uprated' to a 30A one - but that would have been true whether it were a 30A radial or a 30A ring.
It seems that we are probably all agreed that it would not really have made much sense to do that.I must admit, I never came across anywhere where that had been done, but I was rarely involved in any domestic stuff.
Indeed. That was certainly what we had in my youth. Mind you, as time passed, increasing numbers of things were pluged into that one 15A socket by means of 'Christmas trees' of assorted 'adapters'!I might be wrong but, no. Houses had one socket in each room and few electrical appliances on a 15A circuit.
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?To double this capacity, and add extra sockets, by merely extending the end of that circuit back to the fuse-box would require less copper - and no uprating of the existing cable.
That's what I've been saying.I don't really see why that would require the 'invention' of the ring final at all. Two 15A radials would do. They might have decided then to join the two, but why?
I've never disputed that but, as I keep saying, it was really the appearance of fused plugs which facilitated the creation of any sort of 30A sockets circuit (without invoking the 'huge' flex issue).Yes I know, but 30A BS3036 radials required the imperial equivalent of 6mm² - a ring, the imperial equivalent of 2.5mm².
I don't follow the logic; surely it was the proposal/prospect, for whatever reason, of the creation of 30A ring final socket circuits that necessitated the need for fused plugs.I've never disputed that but, as I keep saying, it was really the appearance of fused plugs which facilitated the creation of any sort of 30A sockets circuit (without invoking the 'huge' flex issue).
Fair enough - but, in turn, I'm somewhat struggling to understand why you're strugglingI really struggle, no REALLY STRUGGLE, to follow the reasoning here.
Your memory lane is almost identical to mine (and my memories go back to the mid-50s).First I'll digress and trip along memory lane: ....
As has been discussed, that is almost inevitably the case. Introducing 13A fused sockets for 15A radial circuits would have been essentially pointless, whilst introducing 30A circuits (ring or radial) without also introducing fused plugs would have been 'impractical'/'inconvenient' (would have required 'huge' flexible cables). Hence, as you say, it seems inevitable that they were introduced more-or-less simultaneously, the fused plugs having to be introduced because of the appearance of 30A circuits (primarily the new 'rings').My understanding has always been that the ring and 13A sockets went hand in hand but I'm more than happy if this is not the case.
Fair enough - the reason for that presumably being the need/desire for more sockets? However, as above, when you undertook a conversion, you presumably changed all the sockets to 'BS1363' ones (if that's what there were in those days)?I didn't do any new build work until mid 70's but prior to that I am unable to guess how many radials I converted to rings.
It only matters a jot in terms of the discussion we were having, about the reason for the introduction of the concept of ring finals (a concept more-or-less unlike to the UK and countries historically linked to Britain). My understanding was that it was introduced in the immediate post-war period, when copper was in short supply and a massive programme of new builds (because of the war) was happening - so my understanding was that the primary intent was to reduce the amount of copper used in wiring those rebuilds 'from scratch' (which just about makes sense) rather than in relation to converting radials to rings in existing/surviving properties - not much of which probably happened in the 40s and 50s (and which, in any event, would have little, if any, 'copper saving' relevance).So back to topic. Does it matter a jot which came first (Ring vs radials converted to ring)? I'll bet a pound to a penny that by the late 70's the ratio was about 50:50
As I've said, it was "the proposal/prospect, for whatever reason, of the creation of 30AI don't follow the logic; surely it was the proposal/prospect, for whatever reason, of the creation of 30A ring final socket circuits that necessitated the need for fused plugs.
Who knows. However, per the above, the thinking may well have been that (at least for new builds) having two (or more) sockets on a 30A ring would use less copper than having two (or more) sockets each fed by a 15A circuit. Of course, most countries did not have a post-war rebuilding project on anything like the scale of Britain (hence far less 'copper saving' issues) - although one might have expected that Germany might have felt the need to do something similar.Why, then, did only Britain think it necessary to have 30A socket circuits in domestic properties, the vast majority of which were very small?
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