My god. What is it about this thread? Lets explain simply:
A 1.5mm T&E 30A ring will work effectivey and safely. One of the reasons we use 2.5mm is so that if a cable break occurs, no cable overheating will occur.
In a radial, a bad or o/c connection results in either: loss of power loss of earthing unreliability fire
whereas in a ring, a bad or o/c connection results in: no loss of power no loss of earthing no unreliability no fire no problem whatsoever.
Also, use of 1.5mm T&E cable is actually specifically banned, even when as installed it meets the minimum 20A requirement. A minimum 2.5mm conductor size is specified.
Mike's comment about transport shows just how little he understands the situation. Countries across europe have different climates, different land conditions, fundamentally diffrent social and political policies, and huge investment in different existing standards. The idea of a unified transport system europe-wide is a simple nonsense. It would make no sense to even attempt it.
To elaborate a little:
Some countries spend big on public transport and make it the best there is, some spend as little as possible so that it barely works at all
Some countries have nowt but flat ground to roll along, some have mountains to climb
Some have heavy snow and ice to deal with, some dont
Some need short journeys, some need long.
Some want and expect a prestigious model transport system, some dont give a damn what it looks like, or even that it works properly.
OK. Making the cables thicker would be safer. But it is starting from a position of greater safety than an equivalent radial in the first place.
Wiring rings (or radials) in 4mm or 6mm is actually considerably more difficult than using 2.5mm cable. The cable is stiffer and larger and much more inconvenient to work with, possibly leading to a greater incidence of installation error and crowding within accessory spaces.
I don't think anyone thinks rings are less safe than radials. Just if 2.5mm cable is safe for a 32A ring given the faults that can occur.
IMO it is not. I certainly don't think its safe for a 30A rewireable fuse which is what they installed in my house.
All we have had as evidence that it is safe is talk about "well we know that
2.5mm is rated at 22A but there is a safety margin".
Yes we know that there is a safety margin but its not good practice to use that safety margin under normal operating conditions.
IMO the circuit should be designed so that if a fault occurs it should fail in a way that the circuit doesn't continue to operate or the fuse should be compatible with the capacity of the cable while operating in those fault conditions.
Is this a difficult thing to do? No? So why not do it?
Why don't other engineering professions use the safety margins under normal operating conditions?
With two bits of 2.5mm cable you are not using "the safety margins" under normal operating conditions. Only under fault conditions. Under fault conditions the margins are wider than with a radial.
A 2.5mm radial is fused at 22A isn't it? A faulty but still operating ring is fused at 32A isn't it?
How can there be more margin in the faulty ring?
IMO a circuit that will continue to operate with a fault that is not easy to detect (by the user!) is not a good design. It is unacceptable if while operating in that faulty condition safety is compromised.
Would anyone here suggest wiring a 32A radial in 2.5mm and using it for a decade or two? No you would not.
So how can you maintain that a ring in 2.5mm is safe when you can't tell if it is still a ring and not a couple of disconnected radials? What maintainence schedule do you suggest to ensure that it is still a ring and is therefore safe? Who is going to take the responsibility and for how long? When is the first electrician going to be jailed because he didn't ensure the ring he added a socket to was still a ring? Who will be the next victim? What is the problem with designing things to fail safe?
Eh? We're not talking about under normal conditions, we're talking about under fault conditions, i.e. a broken cable or connection. I'd much rather than a ring with its higher integrity earthing than a radial that can lose earth continuity at the drop of a hat.
You are putting a lot of effort into worrying about something which simply isn't a problem in practice. There are going to be some faulty ring circuits around the country, wrongly wired spurs, and all sorts of other issues. The fact remains that the system turns out to be very safe in spite of such issues, so spending lots of effort making it better has no payback.
Why not find something that really is a problem to worry about? Try thinking about why other EU countries have 3 times more electrical installation fires than we do, for example. There's clearly some scope for improvement there, which has the real possibility of providing a payback.
Since you don't seem to accept the theories other people are giving you, you could also look at the ring circuit and try to work out for yourself why it isn't as dangerous in practice as you believe it should be in theory. The IEE did exactly this recently. One of the things they wondered was if the T&E cable ratings were correct, so they asked the manufacturers to recheck them. It turned out that T&E actually had a higher current rating than people had been assuming for some years, which was one factor which explained why they seemed to be not as dangerous in practice as the prior theory would suggest. I suspect another contributry issue is the quality of electrical accessories used in the UK -- even our worst/cheapest ones are much better than those you'll find used routinely in many other countries. Sure, I've seen the occasional 13A plug/socket that has got hot, but I've seen vastly more of this in other countries, and thats without applying weighting to the figures to allow for the fact I handle more 13A plugs/sockets than foreign types.
Obviously a lot more than you. The transport harmonisation group is up and running and has been for quite some time now. Even the first leaks from it have appeared.
You mean everybody else is/wants to be in the first group and we want to be in the second ?
Anyone with an "old" system gets a new appliance, you would allow it to only be sold with a europlug, how do you think it is going to fit into an old socket? Using a 13Amp adapter?
What power do they have? You have failed to present a single cogent reason for spending hundreds of millions of pounds and killing a few people. Apparently its worth it just for "harmonisation" with some European countries.
Radials are more commonly wired with 4mm^2 and a 32A MCB, not that its relevant here.
Usually yes.
I shall explain yet again for the last time...
All circuits designs can suffer this problem.
Look at the fault categories listed most commonly occurring first:
1) High impedance connection (at a screw terminal typically)
2) Broken CPC (earth) connection (unsleaved thinner wire - so more vulnerable)
3) Broken phase or return wire
(1) & (2) are better handled by a ring circuit by virtue of the alternate path.
(1) on a radial is more likely to cause local overheating at the high impedance point.
(2) on a radial is likely to be undetected and expose users to a significant risk in some cases (especially from indirect contact)
(3) Is the case where the radial performs better (by failing outright), and the ring then relies on safety margin and temporal diversity in order to continuing without undue risk.
Note also that the risks associated with all of these fault categories with *any* circuit type are absolutely dwarfed by accidents and fires that will be created by faulty appliances, stupid users, and extension leads.
This is a nonsensical statement. It is rather like saying it is unacceptable that if the brakes fail on my car it is unacceptable that safety is compromised. Welcome to the real world where equipment failure can and does compromise safety! The solution is you implement dual circuit brakes so you have a fall-back. It does not save you in every failure mode, but it does for some of the more common. Same as ring final circuits.
True. That is why I have not suggested it.
How can you maintain that your car is safe when one of its brake circuits may have failed?
Same with the circuit, in that with absolute certainty you cannot maintain it is safe. However you know from the basic design principles, and from the margins built in that it will remain safe in the vast majority of circumstances.
Depends on the circumstances. If you are talking about a first floor ring circuit with light intermittent load, then it will remain safe indefinitely.
If you are talking about a kitchen in a busy family home with washer and drier in frequent use then more frequent inspection would be good. Say every five years, or at least when the property changes hands. The same advice would apply for a kitchen wired with radials obviously.
Empirical evidence would suggest however that fixed wiring in this country is very safe by any standard, and that is with the bulk of it not being to current regulations, or being subject to any routine inspection.
You ultimately, if it is your wiring.
Or that the CPC was intact on a radial. There is a duty of care on a professional carrying out this sort of work to do so to a reasonable standard. If they behave negligently then they (quite rightly IMO) leave themselves open to prosecution. Whether any prosecutions of this type are ever brought however is another question.
Nothing. In most cases our current wiring practices ensure that is the case. You may not agree, however the empirical evidence is not there to support your viewpoint.
Given limited resources you I would suggest that you don't want to over engineer solutions if in 99.9999% of cases there is no benefit, and it means that resources are diverted from other risk areas that are more likely to result in fatalities.
If there is a 1 in 10 million chance that the fixed wiring in your home will result in a death, and by spending another couple of thousand in electricians time wiring rings in 4mm^2 cable you can reduce the odds to
1 in 11 million is it a good return for the money?
What if there was a 1 in 500 thousand chance of death by falling down the stairs, and by spending the money there with better lighting and hand rails you reduced those odds to 1 in 1 million.
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