With luck, we'll have left the EU by then. It already looks as if the Germans and the Italians are about to jump out of the Euro, and the Dutch are about to do a solo rewrite some of the dafter regulations.
Regards Capitol
It limits RF the noise propagation down the supply lines.
Regards Capitol
You'd be surprised how many banks are still stuffed full of it, which is always a fly in the ointment when it comes to upgrading their computer systems as support for it has been dropped.
There are two possibilities here :
1 : electrical and communications standards bodies are different 2 : you haven't been on a standards committee for several years and things have changedAs I've said elsewhere, there are so many external pressures on communications standards bodies to produce standards that actually work nowadays that nobody is looking to cut corners. Lowering the quality doesn't actually affect the cost much anyway so there's nothing to gain by not producing a good standard and an awful lot by producing a standard that doesn't work and so people don't buy the product.
However I accept this attitude may not have perculated through to the electrical standards guys yet. If this is the case then the governmental representatives should be forcing the issue - that's what they're there for.
And government offices - on 286 PCs :-)
We've *always* been in those probabilities. And they've *always* been low. And they *still* are. They may, with a consumer-gadget-obsessed household, be 10 times higher than they were before. Shock! Horror! That's the way you'd present the increased likelihood to write a newspaper headline. Wouldn't make as good copy if you said "up from 1 in
100 million to 1 in 10 million", would it.Look, it really is *hard* to arrange for a ring to be overloaded *just*
*right* to cause cable damage. You have to get a long-term current of over 25A at least (in the most unfavourable conditions) - 30A for typical UK house construction - to flow in just one leg of the ring, for a l-o-n-g time (1h+?) and for that leg to so dominate the other one that a total current of no more than, say, 42A flows (so the MCB stays put for all that time). Draw too much, and the MCB will pop. Too little, and the cable's safe. Nevertheless, in recognition of this possibility, the Regs have long (a) specifically forbidden heavy, long-term point loads on a ring (no non-instantaneous water heaters, no multi-drop spurs for among others this particular reason), (b) recently had explicit language added to say a designer needs to avoid concentration of foreseeable loads at one end of a ring. (b) has led in particular (even before the IEE spelled it out) to kitchens in more recent builds getting their very own ring, rather'n being lumped into 'The Downstairs'.There's a 'self-balancing', negative-feedback effect which hasn't been mentioned, too. Let's look at what happens as your heavy concentrated load fires up one-ninth of the way around the ring. Fully 90% of the current flows in the short leg, a mere 10% in the long one. (It may even be a little worse, as there'll be more connections along the longer leg, each of which will add a weensy bit of resistance). So, what happens? The short leg gets warmer. And what happens to cable resistance as it warms? Why, it increases. So the 'runaway' doesn't actually happen - a larger proportion of the current ends up drawn by the longer leg, since with the temperature of the shorter one having risen more than the longer, its resistance goes up too. Woop-dee, negative feedback in action.
So, let's see. On the chicken-licken side, we have your call that the sky is falling: that we're sitting on a timebomb of najjerated cable in too too many UK houses, which will melt or burn some time in the next
5-10 years. On the other side, we've extensive engineering analyses (not mine, the IEE's), and an absence of evidence of electrical housefires.But you think we should run around rewiring our rings in 4mmsq anyway, Just In Case; or are you so appalled at the hidden danger of Rings That Go Bad that you want to see ray-gee-alls everywhere, one - or is that several - per room. Got shares in Crabtree, mayhap?
Stefek
Armitage Shanks for one, you know the resident circular pipe manipulating personage is talking about the Open Sink Initiative don't you?
Have you actually worked out what the change in resistance from this warming is? I didn't think so.
Why are you preoccupied with money?
I decided to make this a new thread, just to annoy everyone. No, really I feel a need for a thread title specifically on ring circuit safety, and this'll ge the ball rollling nicely...
Taken from Euro electrics thread...
Mart> > [diversity/ring circuits]
And youd be allowed a whole house total of at most 5 sockets per house on a 60A feed! 4 if you also happen to have lighting. Add a cooker and you might be left with 1 or 2 sockets per whole house. Lay folk may imagine diversity is a dodgy fudge factor, but its really not. Its a fundamental concept of any large elec distribution system, and can indeed be applied entirely safely.
That argument makes many assumptions. The complainants simply dont show any realisation of that.
It assumes that 1x T&E cant safely handle 30A, when it can.
It overlooks the fact that ringing a circuit is a way to make it /more/ reliable and more safe than a radial feed, not less.
It also naively assumes that the idea is to aim for systems that cant go wrong. It isnt, its to aim for systems that very very rarely go wrong enough to kill, and are affordable.
We could spend billions upon billions making our wiring safer with multiple breakers and fuses, RCDs everywhere, backup RCDs in case the first ones fail, multiple redundant paralleled cables, armoured insulation on everything, waterproof plugs & sockets, microswitches in sockets that shut off power if the plug comes out 2mm, AFCIs on everything, triple insulation, 10kV insulation testing on everything, thermostats on all bulb holders sockets and plugs, computerised system monitoring, smoke detection, running all cabling outside the building in steel conduit in case of fire, equipotential bonding in every room, TT earth rod array earthing, and so on.
Why dont we? Because the (close to zero) lives saved by these extra measures would be dramatically outnumbered by the lives lost as an indirect result of us all being poorer, thus having to live with higher risks in other areas, and lower opportunities for medical treatment, safer cars, better diet and so on.
feel free to explain where it compromises. I have the feeling we may be explaining why it doesnt.
I'll bet its saved 200 million by now. Thats about =A36.60 per house in UK since it was popularised. And more importantly, improved safety standards substantially.
With a radial, one dodgy connection can mean a fire. With a ring it means absolutely nothing, it all continues to work happily and safely. Thats a serious plus.
15+5. If theyre both off the same card theyl be the same wire material, and this trick will work. 15A will normally be fine though, the higher current fuses are not known for being in a hurry to act.or the breaker wired over cos it keeps tripping unnecessarily. Its just as easy to do, and breakers are much more prone to nuisance trips than fuses. I bet as breakers spread and accumulate service time, we will start to see more of this, and will come to realise fuses were not the cause of this problem after all.
That would not make a ring unsafe. After a certain amount of i x t the thermal component in the breaker would trip.
very.
NT
We have had PVC insulated cables and 30A rings in domestic use since the late 1940s. How long do you want?
Owain
So use radials for the heating circuits!!! Like we do!!!
We are not discussing dedicated high load circuits with no diversity. We are discussing a *general purpose* circuit for a diverse load.
Owain
obviously it wasnt. MCBs, current balance RCDs, half insulated pins, CFLs are all fairly recent, PVC wire, ring circuits and fused plugs are modernish.
Secondly how old it is is irrelevant, the question is how safe it is. And the answer is that interacting with British fixed wiring is one of the safest things youll ever do in your life.
IOW you dont know of any fresh look that has any better solutions. And you havent taken one yourself.
And btw... there isnt a problem to solve.
NT
Because if every time you want to add a socket you have to add an MCB to a CU, you come within Part P...
Owain
And very good stuff it was too.
Owain
No: instead, I remembered just how significant the derating for ambient temps is for cable capacity, which tells me that rises of each 10 degrees C make a non-trivial difference to R. And that the Regs keep telling me to consider earth loop impedance under fault conditions at full-cable-rating temp. And that the resistance is proportional to absolute temp, which going from ambient of 20degs = 300Kelvin NADI to
70degs = 350K NADI is up by one-sixth.Still, if reasoning from first principles appeals no more than inference from Regs procedures, how about Paul Cook's Commentary On The 16th Edn of the Regs? (He's the Secretary of the Regs Cttee, by the way, so prolly knows a tad more about this field than thee or me). Says the man, p.86/secn4.11: "The resistance of a copper conductor increases by some
20% if its temperature rises from 20degreesC to 70degreesC". (Well, he gets nicer page layout, so can write "20C" ;-)You're right, literally: I didn't calculate it. You're wrong, materially: I knew at the time of writing that it was a non-trivial effect, and have just demonstrated so in three separate ways. (In case you missed them: by inference from Regs procedure; by basic physics background knowledge; by specific quote from a recognised authority).
Oh, and you asked why I was preoccupied with money? It's not a preoccupation, thank you: but *reasoned* application of *limited* resources is at the *heart* of engineering. Not just money: material, energy, inconvenience, and so on. There's a fine quote somewhere about 'any fool can build a safe bridge; it takes an engineer to build one that's safe and affordable'.
G'night - Stefek
snipped-for-privacy@ukmisc.org.uk (Huge) wrote in news:d7sd5l$n92$ snipped-for-privacy@anubis.demon.co.uk:
Which begs the question of whether we would need anything like the number of sockets being talked about - if we were to have, say, power over ethernet or some other 'universal' low wattage supply.
still cant figure out what that means. Nor how it could be correct, since more or less all modern ring circuits have round fuses in the plugs.
nope
it isnt. It is /good/ engineering to use a method that converts danger and unreliability into no-danger and reliability. If you use radials, any disconnections will result in lost earth or power, and bad connections will result in fire. Rings dont suffer those problems as a result of one disconnection or bad connection, thus win all round.
no it isnt.
its the best option we have, and the statistics for deaths caused by fixed wiring in the UK show it is in fact excellant practice.
NT
There are always problems to solve - improved energy efficiency, power factor correction, smart houses, powerline networks, backup systems, brownout elimination, etc, etc
When there's no problems left it's time to go back to the trees.
Aggggghhhhhhhh - should Homebus supply power rears it's head once more :-)
Shame you just did a "reply" and changed the subject then. It's the same thread, to any decent threading newsreader :-)
[...big...]Martin Angove:
Sorry, BS3036 semi-enclosed (rewireable) fuse link.
Hwyl!
M.
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