There's ring & radial. There's 20A & 32A. There's spurs, no spurs and all s purs. There's T&E and MICC. There's flush & surface. How many ways do you w ant to slice it?
There are also obsolete methods very ocasionally found, eg a ring run on 2x 15A fuses, or even more rarely, possibly to the point of never, 4x 15A fus es. Or even more obsoletely, flats each on a single 5A fuse. Seen that one. And no, the electric ovens were not thermostatic.
NT
The question only makes sense if the circuit is wired using "three plate/terminal" ceiling roses when live, neutral and switch wire is present.
Normally the L+N goes from CU to nearest ceiling rose to the next until the last/most remote one and then stops.
But in principle you could wire a ring main. However, the currents involved are so low it would be pointless. Especially these days with LED lights.
There's at least 3 general ways:
1) Ceiling rose loopin-loopout. Supply goes from rose to rose. Switch drop goes from rose to switch.Pro: Simple, easy to get at, roses have all the terminals needed.
Con: Works if you like having nothing but flex drop lights. Random other light fittings may not have the space needed for all the terminations.
2) Switch loopin-loopout. Seen this once. Works with deeper backboxes. Needs a loose connector for the neutral. Not common IME.Pro: Accessible Con: Generally 3+ cables to any given switch. Adds a lot to the overall cable length from end to end.
3) Star wired from junction boxes (what I did). 4 sets of boxes in accessible attic locations. Very uncommon in the UK, though I think some countries do this more.Pro: All terminals accessible and very easy to modify. Very good if you want to include remote control modules for ZWave(etc) which is why I did it like this. Con: More cable
I did ask about ring mains but I take your point.
Thanks. It's getting complicated so I'm going to 'clone' what's there already (and stand well clear!).
terminal" ceiling roses when live, neutral and switch wire is present.
he last/most remote one and then stops.
The point of rings, other than using thinner cable, is safety & reliability .
If we weren't buried in red tape the UK would probably switch to bell wire for lighting with thicker insulation. The ubiquity of LED & CFL bulbs makes 100w per fitting an obsolete requirement. The widespread use of double ins ulated fittings & RCDs along with an all time total of 1 death from a light fitting shock makes lighting earthing redundant.
NT
You still need to be able to trip a 6A type B breaker in 0.4S (typical lighting circuit, not all possible permitted) - and bell wire isn;t going to do that. Given 1mm2 is pretty small and the CPC takes almost no space, it would seem to be an unnecessary change.
I would suggest that this is down to the use of historic cables.
When electric was first introduced into houses it was quite common to use conduit and the cotton covered cables in singles.
When T&E came alone the use of conduit disappeared and the loop in loop out at the light fitting became the preferred method. With the conduit method, to save cable and conduit space you would loop the permanent live at the switches and the neutral at the lights. However singles wiring was still carried on by some electricians who liked it (the picture Terry Casey drew the picture for in the Wiki
ire for lighting with thicker insulation. The ubiquity of LED & CFL bulbs m akes 100w per fitting an obsolete requirement. The widespread use of double insulated fittings & RCDs along with an all time total of 1 death from a l ight fitting shock makes lighting earthing redundant.
no, it needs to be able to trip a 1A breaker in 0.4s. Or 1.5A etc.
the lighting cpc is redundant now. The outer insulation is redundant as lon g as the cable stays hidden in walls, floor spaces etc. Its wasted cost, ma terials, fuel, emissions etc. No-one plugs their iron into the bulb socket anymore.
NT
Tell me - where do you buy these 1A Type B CU breakers?
The main purpose of the the sheath is to protect the *insulation* on the conductors - especially during install when the cable is rough handled, pulled through splintery holes, clipped to rough masonry etc.
There is no way getting rid of the sheath is a good idea.
wire for lighting with thicker insulation. The ubiquity of LED & CFL bulbs makes 100w per fitting an obsolete requirement. The widespread use of doub le insulated fittings & RCDs along with an all time total of 1 death from a light fitting shock makes lighting earthing redundant.
I'm pretty sure the usual mcb/cu suppliers would produce them if they becam e part of a permitted circuit configuration.
long as the cable stays hidden in walls, floor spaces etc. Its wasted cost , materials, fuel, emissions etc. No-one plugs their iron into the bulb soc ket anymore.
Some is, some isn't. 6A to lighting points just isn't needed any more.
NT
That's not a factor of the sheath though. And removing the CPC is pointless in real terms (I don't trust RCDs - they are *nice to have* but I like having a second layer of protection against the live contacting the metalwork on a Class I fitting.) 1mm2 cable is inexpensive, smallish and easy to route. So you're not really solving any real problem.
And your suggestion for the 19th edition of the regs is?
Can't see any advantage... one of the things you require from any fixed cable is some physical robustness. 1.0mm^2 T&E is a sensible minimum.
Nonsense. A standard 6' linear fluorescent is 58W, and twin fittings are common. There are also other things that get run from light circuits like small bathroom heaters, extractor fans etc. So the capacity to support 100W at a fitting is still quite reasonable,
That's just daft. Class I light fittings are common. Plus your normal pet hobby horse of assuming the only bad thing that counts is instant death by electrocution.
My LED tube as 36W.
reducing costs is itself solving a problem. We all want life to be more affordable.
NT
reducing cost. Doing so gets us an ever better material standard of living year on year, and enables more to be spent on the nhs etc.
depends what you're doing with it. There are many cases where bell wire is strong enough.
those can go on 5A circuits
but not any significant risk. Time has proven that. And now we have een more safety protection on lighting circuits than in the decades that proved them not a problem
whoosh. Death rates are used partly because it's the one thing we have genuine reasonably reliable data on.
NT
100m drum of 1mm2 T+E is £22+VAT right now.
100m of 0.4mm2 actual bell wire is £8.99
You've saved £13+VAT on a house build. Bravo sir :)
The 30a ring main for sockets was devised post WW2 to save copper which was in short supply.
The big safety feature is the individual fuse in every plug.
It is in fact less reliable as all your sockets are on one fuse/MCB.
A few years back, the EUSSR was trying to make us go back to similar system to that we had abandoned in the name of "harmonisation".
They don't have to be.
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