: > : : > : Never mind - it'll ne OK when you finish Key Stage 2. : >
: > Just because you are still at Key Stage 1, repeating, : > unquestioned, all your are being told parrot fashion, you think : > everyone else is... : : just because you have fished stage 2, don't assume that those of us with : degrees in electrical engineering and a lifetime of dealing with : electrical circuits haven't thought about it just as much as you have, : and don't need to be patronised. :
Just because you have learn to act like parrots, repeating ad-nausea what your owners tell you, rather than use your brain cells... It was people like you who held industrial manufacturing/development in the UK back for so long, allowing others to have the blue "skies thinking" that turned much of the UK Plc into not much more than assembly lines at best and importing/warehousing agents at worst.
Yes, and I have said that both radial and ring circuits have both advantages and disadvantages.
Plug fuses can be abused (as can rewireable fuses : in consumer units), however in reality this much less of a problem that : might be imagined.
But we are talking about (theoretical) risks, allowing the ignorant to defeat final protection with not much more than a kitchen or pen knife and thus compete for a "Darwin Award" has a very much higher risk factor than many of the risk that the regs are obsessed with now!
Most appliances are designed to be sold all over the : world, and hence will usually have a flex that is capable of surviving : faults with only 16A head end protection (as would be common in some : countries),
Not so sure, whilst many appliances are sold all over the world, since the UK law has required the pre-fitment of BS1363 plugs complete with the correctly rated BS fuse many appliances now come with power leads not only with moulded on plugs but the lead rated to the fitted fuse IYSWIM.
hence the fact that someone might substitute a 13A fuse in : place of a 3A is not likely to be a problem with most appliances. There : is the remaining issue that one could substitute a solid object for a : fuse, but that does not appear to be something that happens regularly. : Quite possibly because it is very rare for plug fuses to blow in the : first place.
How do know the practice is rare or not, only when something goes dramatically wrong will the miss-use ever become apparent and if protecting an appliance with a grossly over-rated device (15A or even 30A instead of 3A) isn't really that much of a problem then the rational behind the original design of the BS1364 plug/socket must be in question! Also any appliance that does need careful protection should perhaps have to have a 'tools-only' accessible internal fuse anyway?
: : The absence of a plug fuse requires that the protective device at the : head end of the circuit can clear not only overloads of the whole : circuit, but also faults that may occur in light weight appliance : flexes.
But that IS the way things are going anyway, hence stories of RCBs tripping out because someone has pluged in a doggy table lamp in one room and taking out the supply to someone using a computer in another and thus their unbacked up work - and don't suggest that they should have had the computer on a differant ring circuit, "Average Joe" and his family use what the builders/electritains have installed.
This second requirement places significant restraints on the : circuit as a whole, and drastically limits the total power supply : capability. Hence the proliferation of inflexible[1] low current rated : circuits you get in places like the US. : : [1] Think about a kitchen / utility room with tumble drier, dish washer, : and washing machine. That could represent 8kW of load - although it : would be diverse - the chances of all three being in use at one time is : relatively small, and the presence of thermostatic controls on the : heaters will mitigate further. These could safely be power on one 32A : ring circuit, but would probably require three 16A or 20A radials to do : the same job. :
Indeed, or perhaps even a sub-main feeding a sub-board. Also, remember if these appliances/utility room is feed via it's own ring circuit this requires two of the two out of the three cable runs needed for the radials anyway, cost savings will be minimal and thus I would prefer the redundancy given by radial circuits, also radial circuits and 15amp unfused plugs would remove the issue of either BS1363 plugs stuck behind these difficult to move appliances, plug and sockets being fitted in cupboards, trailing leads or hard-wired flex outlet plates.
Most owners don't care how many, or indeed the cross section of such, wires have been installed in a building (even the fitment of 5amp lighting points in the wall), what they do notice is price (of new house or re-wiring a old house), so the choice of ring vs. radial circuit comes down to cost at the end of the day, not really the technical pros and cons of each.
Well, perhaps, but then I live in the real world and not that perfect world that you seem to inhabit, were if something is meant to happen it always will, like all company supply neutral fuses having been removed by the mid 1980s or that the BS1364 plug will always have the correct fuse installed, or indeed any fuse...
: The [UK] system is cheap to install and extend, : safer than American and European systems, more : flexible and efficient.
The only true statement in the above is the words "cheap to install". The problem with North American system is more to do with quality (of the components used) rather than the design of the circuits, same is true of European systems added to issues of workmanship [1]. How is someone in the UK being able to protect their 3amp table lamp via a bolt (or indeed a 13amp fuse) in the BS1363 plug and the 20 to 30A CB at the D-board any more safe than someone in either the US or EU plugging the same 3amp table lamp into a wall socket protected at ~15amp CB at the D-board?
[1] and shoddy workmanship is also a problem in the UK also
: > : > :> Ring circuits and fused plugs were introduced in the UK : > : to save copper etc. in the post-WW2 rebuilding programme, : > : they have a number of disadvantages. : : > : Which are? : : : No offence Jerry, but this is a load of ill thought out twaddle. : : > I take it that you have never come across the bolt being used as : > a 'fusible' link within the a Bullshi... sorry BS1363 plug that : > is feeding a device that draws< 3amp via a similar rated length : > of flex. : : Being able to abuse a fuse in a plug is not a fault of ring circuit.
No, it's the fault of the regs that allow the design of the circuit and/or the hardware.
The : circuit in question could be a radial, and the circumstance would be no : more desirable.
Not so, radial circuits would be/are more tightly protected, a
15amp CB rather than the 20 to 30 amp CB fitted to ring circuits.
: : > I take it that you have never come across the situation were an : > faulty appliance fails to blow the fusible wire within the : > Bullshit... sorry BS1363 plug but trips out the much more : > sensitive CB on the panel, taking out all other devices connected : > to that circuit (which in a house can be the entire power : > circuit. : : Again, this is nothing to do with circuit topology. As a general rule, : overload related problems are more likely to blow the plug fuse, and : hence result in "perfect" discrimination (i.e. the only device losing : power is the faulty one). Fault (i.e. short circuit related) may : occasionally trip a circuit breaker in the consumer unit. However again, : this has nothing to do with circuit topology, the same could happen with : a radial. : : If you follow US practice for example where the only protection is at : the origin of the circuit, then you can be sure to de-energise the whole : circuit for all faults (either than or have to work out how to get at an : internal appliance fuse).
Oh, so taking out just a room rather than a floor (as is usual with a ring circuit) is worse?!
: : > The ONLY two advantage of ring circuits is installation cost and : > smaller size of fuse/CB panel. : : In fact neither of these are true now. Installation cost, when : installing from scratch is not significantly different.
But was when the UK ring circuit was first designed and introduced, now the ring has just become the day-facto standard and is often installed without (prior) thought.
Also remember : than in the UK we can have 32A radial circuits if required, so there is : no particular advantage in reducing the number of ways in a consumer : unit either.
But the use of ring circuits HAS resulted in a reduction in the number of ways in the average domestic D-board.
: : It is important to realise that what started as a way of saving copper : after the war, has been refined and improved over the years, to what we : have now, which is a circuit that is very well suited to modern patterns : of use.
Has it been refined, *circuit* protection might have been refined and this has allowed a refinement in conductor size etc. but the circuit design and end appliance protection hasn't been refined that much if at all.
The ring circuit is also well suited to provision of power for : "diverse" loads - i.e. large numbers of appliances can be provided for : over a large floor area, and also higher power devices can be included : in that mix without fear or overloading a circuit.
Err, one can only use, either, the number of appliances up to the total number and rating of sockets or the total rating of the circuit, the same is true of radial circuits. 'Diversity' is applicable to the loading of radial circuits as it is to ring circuits.
Alternatively they : also cope with applications where many high power appliances are used in : proximity such as kitchens, where the ability to provision for
7.2kW of : load without needing unmanageable cables sizes is a great advantage.
Sorry but that sounds somewhat like a straw-man argument, how many domestic kitchens would draw that sort of (non "diverse") load [1] and if we are talking about industrial installations then running radial circuits via a sub-main and sub-board could be as convenient, with the added advantage of appliance redundancy - not having the one out all out total failure of a ring circuit tripping out.
[1] and as has been pointed out elsewhere, if 7.2KW of non diverse load does need to be supplied then 2/3rds of the cabling needed for three radial circuits would be needed in a dedicated ring circuit anyway.
: : You have a circuit that behaves better under most of the common failure : modes in circuit wiring (i.e. high resistance or broken conductors), and : retains higher levels of protection under most of these failure modes.
In other words, what you seem to be saying is, the ring circuit is good at masking (possibly) fatal faults, such as a disconnected conductor, thus the circuit has the same load on a single 2.5mm T&E rather than sharing the load between two sets of such conductors...
: : For a full description see: :
formatting link
Ring circuits typically have lower earth fault loop impedances as well, : result in quicker clearing of faults. :
Why should that be, and what would need to be changed in a radial circuit spec to mirror the results found in ring circuits?
: : It takes a lot of effort to create a solid metal replacement for a : fuse.
No it doesn't, not for a BS1363 plug, just a hacksaw and a suitable bit of metal (such as the common 8mm bolt found in so many cheapo DIY packs of 'essential' DIY fixings as sold by the sheds, TV channels and even supermarkets. Bloody idiots for doing it, but that is how easy it is. :~((
: Easier to get a fuse.
Not if the frecking appliance keeps 'popping' the highest available fuse...
This pre-fitment of BS1363 plugs only applies to "domestic" appliances. I've bought a number of theatre 'luminaires' (lamps!) without plugs on the end of their flex.
Actually the use of BS1363 plugs for such lamps isn't a very good idea at all. They're normally connected to a radial circuit from a dimmer pack which has fast-acting fuses to protect the triac dimmers. If a plug-top fuse was to operate for any reason it would be a major inconvenience to move an audience out of the way to get a step-ladder into place to change a rogue fuse in the middle of a play.
Surprisingly many of these lamps are connected via good old-fashioned
I believe there is EU regulation that requires flexes to be adequately fault protected by a 16A fuse/breaker. (which is not the same as being deigned to carry that as a nominal current)
Well I know that fuses in plugs blow very rarely - since I and most other have to change one very rarely. (some folks suffering high mains voltage probably get more than their fair share - but I don't recall needing to change a fuse in the last ten years).
13A is the largest fuse you can get for a BS plug.
The plug fuse is there to protect the flex, not the appliance. If that needs further protection then it can have its own internal fuse.
Well if the RCD tripping prevented the electrocution of the table lamp user, then loss of data is probably a fair enough price to pay ;-)
The move here it toward using RCBOs for most circuits (i.e. combined circuit breakers and RCDs). This maximises the RCD protection while keeping the discrimination tight.
Lots of smaller circuits (ring or radial) would mitigate this further, but one needs ot consider the cost benefit trade off again. The builder / electrician will be primarily concerned with ensuring basic safety, not maintaining supply continuity, which is a non issue for most household appliances. Computers are an exception, but if one cares, one can use a UPS, rather than increase the wiring costs for all dwellings.
Indeed, as I said before, cost is not really a primary driver.
If you have a bunch of radials feeding different groups of circuits, then the user now needs to be aware which sockets are on which circuits to ensure that the loads are distributed between them.
A single more powerful circuit (32A ring or radial) gives more flexibility with less onus on the user to know how the place it wired.
Not sure I follow what you are saying? Do you mean that having an unfused plug would save having to pull an appliance out to change a fuse?
Indeed it might, but since there is no reason for the fuse to need changing unless the appliance has a fault in the first place it seems like a moot point.
Its a bit deeper than that if you are doing the design exercise properly. Rings are handy because they let you wire for modern useage patterns easily, and festoon are area in sockets for AV kit, computer etc. But one also needs keep in mind likely uses of sockets and layout when selecting circuits. Additional circuits dedicated to specific uses often form a part of the design.
Would they? A 32A radial would be no more tightly protected generally.
We tend to use 16A and 20A circuit breakers for small radials (16 more for task specific jobs like feeding an immersion heater or some other non diverse fixed load, and 20A for general purpose socket circuits). One can also use a 32A breaker on a radial if its wired in a heavier cable (typically 4.00mm^2 T&E). This is not a commonly used circuit, but can make sense if a ring would be unbalanced, or the layout makes the return leg particularly difficult to implement.
Oh so taking out a room, rather than just the plug fuse for the appliance in question is better?
It was by virtue of it allowing adaptation and re-use of existing wiring
- two 15A circuits could be combined into one that could reasonably used to heat a storey of a property. If laying in cables from scratch there is not much in it.
Given it has proved its versatility and safety, then that is probably a good thing.
Compared to what?
40 years ago a domestic house probably had a four or five way board if you were lucky. These days 8 - 12 is more common.
The basic circuit design is similar (but much more research has been conducted into understanding de-rating factors resulting from cable grouping, ambient temperature, installation method etc, and into understanding the appropriate limits to circuit length (due to voltage drop or earth loop impedance)). Cable earth conductor sizes have been changed in places, and fuses have generally be replaced by dual acting miniature circuit breakers. RCDs are now used extensively.
What has changed massively is modern usage.
A few years ago I rewired a neighbours house. It had its original wiring as installed in the early '50s (plus a bit of bodging from the owner!). It was instructive to see what constituted a typical electrical installation.
There were four circuits in total - two lighting, two power (the power circuits were radials wired in rubber sheathed cable with a separate bare earth wire). Each power circuit fed approx 4 sockets - giving a total of 9 for the whole house (and these were all single sockets).
When we designed what was needed for their actual usage, we ended up with something like 34 double sockets. That was three rings (upstairs, downstairs, and kitchen), two lighting circuits (one per floor), and high integrity radial with its own dedicated higher threshold RCD for the freezers, CH boiler, and fish tank, plus a sub main feed for the outbuildings.
One could have slapped in a a few extra radials for each floors sockets, but it would have added little of any great value. Its unlikely the circuit breaker for any power circuit will ever trip. If the CH fails, and they want to plug in a couple of 3kW heaters, then they can do that pretty much anywhere, without fear or tripping something. Meanwhile should a wire work loose somewhere, there is a reduce chance of overheating of loss of earthing due to the redundancy of the ring circuit.
Diversity applies to both, however the more floor area covered, and the more appliances in question, the more diversity there is.
Domestic kitchens with an appliance load of 9 - 12kw are common here. Most will have dish washer, washing machine, and drier, and each of those will often pull 2 - 3kW. On top of that many single ovens up to a couple of kW are designed to "plug in". A kw of microwave, and on top of that you will usually have a few "small" appliances like a 3kW kettle, and 2kW toaster etc (you can ignore those from loading calcs since they are such short term loads). There will often be dedicated 32A or 40A radials for cooker supplies where electric cookers and hobs are installed.
(its worth noting that the easy availability of a 3kW supply to an appliance means the appliances available and commonly used are different from in some countries. So in places like the US electric kettles are much less commonly used due to lack of power, and "wet" appliances usually have hot fill etc to save needing to heat water locally and slowly etc).
Again we keep coming back to "rings tripping out". As a general rule not something that happens with great regularity.
The most common "trip" problem we tend to get here is with RCD trips caused by faulty appliances (or damaged wiring). Neither of which are going to benefit from being ignored from prolonged periods.
yes, and?
The most common fault is a high resistance connection (loose screw terminal etc). You will tend to get less serious overheating on a ring, and usually no increase in fault disconnection times.
The next most common fault is a broken earth conductor (its thinner and uninsulated), again a ring carries on safely while a radial will have a proportion of its sockets without any earth.
The next most common is a broken live or neutral conductor. Here a ring
*can* mask the condition where it should be apparent on a radial. However on most real world ring circuits you would still probably get away with a fault like this without anything serious happening.
Needless to say you can't always have the best of all worlds, so it seem preferable to me that you use what performs best with the most likely faults and that is the ring circuit.
formatting link
:
A radial will typically be wired in 2.5 or 4mm T&E, both of which have a
1.5mm CPC (earth), a ring in effect has two of them in parallel. Hence the fault loop impedance tends to be lower on the ring due to the area of copper involved.
Radials can be wired with what is called high integrity earthing - here the CPC is returned to the origin as if it were a ring, and also the two earth connections to each socket are made to independent terminals on the socket. This system is usually specified for when it is known there will be high earth leakage currents - typical with lots of IT or other electronic kit where there are lots of mains input filters sticking capacitors between line and earth.
With regards dealing with the effects of loose connections, there is not much you can do with a radial intrinsicly to improve it, other than specify more frequent inspection and test, and to ensure a good standard of workmanship is maintained during construction.
How many people do you know who would go to the bother of finding a bolt of the correct diameter and cutting it to length just to avoid fitting a fuse? An incorrectly rated fuse is a far more likely scenario.
I can think of numerous devices that come with various gizmos to adapt them to a number of plug styles, rather than pre-fitted or moulded-on BS plugs. Sometimes the BS style pins slide on and lock into place, but are not pre-fitted. Others have a clamshell style adapter that fits around a euro style two pin plug.
All carry CE marks and were purchased in the UK. Unless there's a massive conspiracy among manufacturers and/or importers, then I thinnk the UK law must have been relaxed or re-worded somewhat.
one in this thread is claiming that abusing the system is any safer, only that the incidence of such behaviour leading to a "problem" is so small as to be an acceptable risk.
I've worked on countless North American installations and equally on countless UK installations.
My conclusions?
North American installations do indeed tend to use components -- especially wall receptacles and plugs -- of unbelievable crudeness and totally-deplorable quality. Quality components are available, but absent from almost all domestic installations. The electricity supply isn't up to the job -- sadly, 110v and the consequent high current draw means that there are rarely enough circuits and tripping the breaker is an everyday occurrence in a very large proportion of installations. 220v is needed anyway, for the stove and dryer, not to mention air conditioning units. Surprisingly, switches are remarkably long-lived and some good ones are readily available. And the ES lamp socket is inherently a better socket design in physical terms than a BC one.
I'd much sooner live with UK installations. Ring mains and BS1363 are both IMHO very much superior to other practices. The horrendous weakness of UK installations is to be found in BC22 lampholders which in domestic use are almost invariably made of cheap and nasty plastic which disintegrates very rapidly. BC lampholders CAN be properly made -- and indeed I replace failed plastic ones with brass+porcelain ones which are just fine, but really, the design is flawed.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.