Like many - I've had plenty of 240v belts, and a rare few 415v ones. The 240v I can shrug off, the 415v ones burn, and are not so easy to shrug off..
Ring main troubleshooting
- Thread starter KPX33
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Like many - I've had plenty of 240v belts, and a rare few 415v ones. The 240v I can shrug off, the 415v ones burn, and are not so easy to shrug off..
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Same here, in the very distant past - and, indeed, some 1,500V+ ones. However, they were all extremely brief in duration, which I presume is why I survived them. Unless they had very dry 'rhinoceros skin', I doubt that anyone would survive a sustained 200V shock!
Furthermore, as we often discuss here, attitudes to safety/risk have changed dramatically over just a few recent decades. The decisions (about voltage) were presumably made a century or so ago, when I suspect that very little thought will have been given to the 'risks' involved - so I still do wonder what actually was the basis of the choice/decision.
It's possibly worth stepping back and looking at the pre "RFC with BS1363 sockets and wired in 7/029 and protected by 30A rewirable fuse" days.
I suspect that for many, the idea that you could have sockets in every room, and more than one per room was a massive leap forwards. Granted, it could gave been done with radials - but that would have needed a larger cable as having multiple sockets on a 15A fuse wouldn't have been acceptable at a time when multiple electric heaters was a common situation. Having worked with 7/036 (radials in our church), it's almost as awkward as working with 4mm - and as already mentioned, the RFC was designed during or shortly after WWII when copper (like many things) was in short supply.
So as mentioned in the past, the RFC allowed a major step forward from having only a couple of sockets in the whole house.
When discussing options today, remember that we now have 20A, or 25A from some manufacturers, MCBs (closer protection than rewirable fuses) which allows radials with a decent current capacity while still using 2.5mm cable - and in general we don't tend to use a lot of portable electric heaters.
I just point that out since many seem to have forgotten the context in which the RFC came about. It helps understand why RFCs were "the norm", but radials are coming back into fashion.
What do you mean by that? As I often say, I personally find 4mm² T+E nicer to work with than 2.5mm².
A good few people these days advocate 20A (2.5mm²) radials (with lots of sockets) - so I'm not sure that 15A ones back then would have been all that much different, would they?
What has changed is the realisation that having lots of sockets does not mean that there will be lots of large loads plugged into them. Had that thinking not changed, every double socket would presumably have to be on its own dedicated circuit
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Matter of preference, but it's larger and (for same construction) stiffer.
Edit: it is "interesting" getting it all into the terminals when there's a 2.5 spur off a radial wired in 7/036 - so about 12.5mm of copper to fit in !
What happens to your 15A radial when two electric heaters get plugged in ? One of our churchwardens failed to see why it was a problem as he'd "used two different sockets".
Changes include central heating, and lots of small loads.What has changed is the realisation that having lots of sockets does not mean that there will be lots of large loads plugged into them. Had that thinking not changed, every double socket would presumably have to be on its own dedicated circuit
Yes, but the point is that they are not "of the same construction". 2.5mm² T+E has solid L+N conductors, but 4mm² has stranded ones, hence less stiff. As for the external size, I often have to look two or three times before I'm sure which I'm looking at!
I think you may miss my point, since I could just as easily ask ..... What happens with a modern 20A radial (with, say 6 or so double sockets) has multiple electric heaters plugged in?
Just to add that in my youth 3KW fan heaters were quite common rather than the 2KW of today,
Two such heaters plugged into one circuit and you`d taken most of a ring`s amps up anyway.
Plus it was not by any means uncommon to have a 3KW immersion heater connected to the ring either.
Two such heaters plugged into one circuit and you`d taken most of a ring`s amps up anyway.
Plus it was not by any means uncommon to have a 3KW immersion heater connected to the ring either.
That reminds me.
As above with the 2.5 T & E ring final and a 3KW immersion heater as a spur in 2.5 and nobody blinked about it much.
How does that compare with one I saw a few years back in a residential home?
6.0 T & E 32A circuit feeding two 3KW immersion heaters.
The EICR inspection firm had failed it because the 6.0 went to the first immersion isolator then in 2.5 to the second isolator, citing overload if I remember correctly. How does that compare to the immersion heater spurred from the ring?
Actually, this particular firm, I was quite used to seeing their garbage reports, a plethora of things defected there were not defects and a plethora of things totally missed, some pretty bad indeed.
In fact if I stood in a property and read its PIR/EICR I would wonder "Has this cert got the correct address on it?" glibly I might add.
They were about the cheapest in the area, did loads of them, the boss had them doing at least 3 PIRs per working day (submitting their inspections to him on a bit of paper then he filled the certs back at the office) he was always pushing them to do 4 a day.
I never saw one of those that gave much resemblance to reality.
If any organisation used to ask me what was required from reading one of those, I would see the name on top and comment "Put it in File 13!" . A lot of office staff use the name "File 13" when they actually mean the litter bin.
In fact, a colleague of mine, electrician but not NICEIC or anything and just prior to Part P coming in had asked the owner/qualifying supervisor of this firm to do an EICR on a house he`d recently rewired to aid with selling it. he gave him the keys and confirmed the time he was coming so my colleague decided to call in and wait for him, he waited and waited to no avail then later on rang him. He said he had been approx 20 mins early.
So 20 mins top side to do the PIR .
My colleague had the C & G 2380 like me but unlike me he did not have the C & G 2391. Anyway we went thru reading this PIR and both declared it to be renamed as "Billy`s Weekly Liar" ( a humorous newspaper you could buy at a Joke Shop years ago - many years before the Sunday Sport had such brill headlines as "WW2 Lancaster Bomber flies to high and crashes on the Moon" and other such absolute gems, Brill).
As above with the 2.5 T & E ring final and a 3KW immersion heater as a spur in 2.5 and nobody blinked about it much.
How does that compare with one I saw a few years back in a residential home?
6.0 T & E 32A circuit feeding two 3KW immersion heaters.
The EICR inspection firm had failed it because the 6.0 went to the first immersion isolator then in 2.5 to the second isolator, citing overload if I remember correctly. How does that compare to the immersion heater spurred from the ring?
Actually, this particular firm, I was quite used to seeing their garbage reports, a plethora of things defected there were not defects and a plethora of things totally missed, some pretty bad indeed.
In fact if I stood in a property and read its PIR/EICR I would wonder "Has this cert got the correct address on it?" glibly I might add.
They were about the cheapest in the area, did loads of them, the boss had them doing at least 3 PIRs per working day (submitting their inspections to him on a bit of paper then he filled the certs back at the office) he was always pushing them to do 4 a day.
I never saw one of those that gave much resemblance to reality.
If any organisation used to ask me what was required from reading one of those, I would see the name on top and comment "Put it in File 13!" . A lot of office staff use the name "File 13" when they actually mean the litter bin.
In fact, a colleague of mine, electrician but not NICEIC or anything and just prior to Part P coming in had asked the owner/qualifying supervisor of this firm to do an EICR on a house he`d recently rewired to aid with selling it. he gave him the keys and confirmed the time he was coming so my colleague decided to call in and wait for him, he waited and waited to no avail then later on rang him. He said he had been approx 20 mins early.
So 20 mins top side to do the PIR .
My colleague had the C & G 2380 like me but unlike me he did not have the C & G 2391. Anyway we went thru reading this PIR and both declared it to be renamed as "Billy`s Weekly Liar" ( a humorous newspaper you could buy at a Joke Shop years ago - many years before the Sunday Sport had such brill headlines as "WW2 Lancaster Bomber flies to high and crashes on the Moon" and other such absolute gems, Brill).
That's a modern abomination. 2.5 T&E used to be stranded as well - and was much easier to work with. I think 4mm had more strands than it does now.
Edit: and in context, it would have been a choice between 7/029 and 7/036 - so same construction, thicker strands. Modern unstranded T&E is an abomination by comparison.
Exactly - and it would gave been 15A goibg back. But as ebee notes :
Plus, as I noted, most houses have central heating so we use portable heaters MUCH less.
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Isolator or fused switch ?
The 2.5 spur off the ring would terminate with a BS1362 fuse so overload protected.
If the circuit described had isolators rather than switch-fuses, then there is a foreseeable overload situation (immersion element short to casing results in higher load current until either the element or fault burns out, or and RCD trips). So in this case the defect report could be correct depending on the answer to the question above.
'Lots of 15amp' sockets, predate me, but I always assumed it was one socket, one radial, one fuse?
At odds, with experience - 2.5 was much easier to handle, than either 7/029, or 4mm
Stranding, only works in fixed ratios - 1, 3, 7, 19 (I think?)..
I disagree, no overload protection required for a fixed load is the general opinion of the great and good.
Yes it is conceivable, however unlikely it may in reality be, that an element could short, however for such fixed loads it is ignored and therefore just short circuit and earth fault to be considered.
In effect, we always assume that a short circuit or an earth fault is via a "bolted fault" (zero resistance/impedance) whereas in real life this is often unlikely to be the case.
In other words, we are only expected to go so far. in our safety calculations and not really account for, example, light touch by a rusty nail scenario as it would severely beggar up all our calculations with extreme vengeance.
I would not use a SFCU on an immersion heater
It was in the days of unfused 5A & 15A sockets. That changes with 13A fused plugs.
Yes generally. Is 4mm generally 3 strand ? That's going to be stiffer than 7 strand 7/039
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