From http://www.cirris.com/testing/temperature/copper.html
So don't ask any electrician trained in the last thirty years or so...
How? The only way you can meet the requirements of regulation 433.1.5 is by you, the designer, ensuring that the positioning of sockets is such that it is not possible, via 13A-fused plugs to create an overload situation. If you do this, then there is no need for your way-too-elaborate and ill-conceived arrangement.
What on earth do you think people want to plug into your socket circuit? Sensible design tends towards fewer points on a greater number of circuits, rather than, as you seem to be suggesting, a greater number of points on fewer, uneconomically designed circuits.
No, it doesn't. It really doesn't in any practical sense.
Non-sequitur. Irrelevant to your argument.
Responses:
Yes, I think we got the message, you will NEVER under NO CIRCUMSTANCES work on a ring main circuit. Unfortunately, that leaves you with a single double gang socket on each 20A circuit unless you like explaining why the consumer can't plug things in where they want. We've already covered that double gang sockets should be protected to 20A.
.You obviously didn't get the message though. For, say a kitchen, where the plugged-in loads are known, rarely altered and the socket positions relative to the consumer unit position are easily designed to be in the middle portion of the ring without unnecessary lengths of additional copper cable, the current ring circuit design can be a good solution to serve the kitchen alone. (Although an additional worry is the very few installers who know how to test such circuits correctly)
A 20A ring final circuit on 2.5 sq mm pvc cable may serve an unlimited number of socket outlets over a floor area of 50 sq m. That's easily enough to cover the first floor of most houses. Alternatively a 32A radial socket circuit with 4.0 sq mm cabling may serve up to 75 sq m. Maybe you don't understand the concept of diversity, but these circuit arrangements have proved themselves over years of use.
I see where you are confused. I never mentioned Europe. I meant that we should opt for radials as the first choice, only considering rings where we have a really good reason to do so. A good reason would be fixed, high loads on circuits of great overall length, such as, say stadium floodlighting.
It's not a ring main - they operate at 11,000 Volts generally - it's a ring final circuit.
See, there's part of the problem. I'm sure 'thecommiser' isn't a bozo, but he seems to think his lights are wired in a ring. This is quite common. We don't want even more confusion out there, do we?
So, if I understand correctly, for an uncontrolled ring final, assuming a CCC of 20A and an MCB of 30A, you would want the sockets to be in the middle 1/3 of the cabling. You have mentioned extra cable, which I surmise ensures this design 'rule'. This also makes it more likely for a ring final to become too long - so you may need more circuits to keep them short.
A couple of fan heaters, a hair dryer, iron and plasma TV at least.
With my hypothetical quad-pole RCBO, there is no need to make the design "uneconomical" as both ends of the ring can supply at least 20A (which is suitable for living rooms) and the middle of the ring can supply up to 40A (which is suitable for kitchens).
1. OK, with your 'centre 1/3' rule as I have inferred. But it frees designers of that constraint and/or the assumption of even distribution. It completely eliminates the possibility of localised load overloading a single cable. It also protects the cable in case of a continuity failure. An MCB only directly protects the live conductor(s), my suggestion protects all 4 live and neutral conductors - isolating the whole ring final on any overload.
On the contrary, I am suggesting a circuit protection that is easier to design with - no consideration needed for portable load distribution nor individual cable lengths. Sockets close to the CU can be supplied by a short cable carrying most of the current because that cable is individually protected.
I can see there might be some benefits (although not as many as my hypothetical suggestion). I already have one 20A radial supplying fixed loads in the kitchen (washer, boiler, cooker hood and gas igniter). The portable appliances in the kitchen are supplied by the centre of the single ring final.
(a) and (b) OK
That's about the size of it. Because you can't be sure what will get plugged into which sockets, the only way you can ensure a reasonable load distribution is by avoiding clusters of sockets close to the start/end of your ring.
So, you propose a circuit design which now requires people to understand what load they can attach, depending on the geography of your socket layout. I think you'll find that users are neither interested, nor capable of understanding this concept.
No it doesn't. it means designers and installers will have to guess where the bigger loads might be concurrently applied and you could end up with some very interesting cable routes.
At the expense of a level of complexity which is neither sensible nor required - because a radial socket-outlet circuit will already do the job without any special rules for how the circuit is used.
By converting a strange kind of a ring into a lower-rated radial.
Single-pole isolation is both safe and normal, but if you want to isolate both live conductors - that's line and neutral - feel free to procure a caravan consumer unit.
No. Rings always use more cable than you would use if you supplied the same demand through radial circuits. That's one of the things they really got wrong back in 1947.
Quite right. If you read Reg 314.1 you will see that rings are not even mentioned. This still does not mean that a ring final circuit should be the automatic choice for socket-outlets.
No, you're not. Keep it simple. Rings are not only not simple, they are fundamentally flawed in design, poorly installed, rarely tested and are only tolerated by the use of a 'deemed to comply' regulation which almost nobody seems to follow.
I appreciate that Electricians don't generally have Physics A-levels or Engineering degrees.
No, there isn't.
Don't be ridiculous.
Don't be ridiculous.
What - all at once? What kind of house has all those going on in the same room?
What's hypothetical about it?
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