lighting circuit help

I replaced a standard light pendant and although everything works I am slightly confused about the light circuit. The celing rose consists of three separate cables (one double core, the other two both single core). One of the double core cables goes to the live junction in the ceiling rose the other to the earth connection. Both single core cables (twisted together) go to one of the neutral junction terminals (nothing goes into the loop section of the ceiling rose).
The only idea I came up with is that the neutral loops round all the ceiling roses and the same thing happens on the live side in the switches (which in the room where I replaced the pendant also has three separate wires going into the switch). So I have a ring lighting circuit?
But again I am not sure so any suggestions are welcome
Thanks
Nick
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Nick
Is your house 1970's ish construction? I have a property of that period similarly wired. Live loops around switches, neutral between ceiling roses - quite confusing till you get your head round it! Wouldn't suprise me if this was done for cheapness. With new additions to mine, I've tended to adopt modern wiring protocols (rightly or wrongly).
Phil
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On Thu, 29 Jan 2004 13:52:26 -0000, "TheScullster"

That is modern protocol, just not as common as the 'loop-in' method. It's not wrong, just different. It's a lot easier, both on 1st and 2nd fix, always has been, always will be. I find it a lot easier to do it that way, especially when there are quite a few different switching and lighting arrangements in one area.
SJW A.C.S. Ltd.
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It sounds less than wise to me, because you end up with unbalanced currents in different cables. Wouldn't this do undesirable things where the cable was (say) in a length of metal conduit?
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wrote:

Basically, no. Off the top of my head it could get a little complex trying to explain here, I might come back later! If anyone else wants to have a go in the meantime then go ahead.
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Yes, it's not allowed in steel conduit. In theory it causes edie current heating if the wires enter steel back boxes through different punchouts, but I doubt it will be significant enough to notice at domestic lighting circuit current levels.
Another reason you aren't supposed to do it is it stops induction loop hearing aids working, and this can affect neighbouring properties too. Unbalanced wiring layout of 2-way switched landing lights is a common cause of this problem.
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It is wrong. It probably should be banned under some sort of Disability Discrimination Act. It will totally bugger up any hearing aid inductive loops when the lights are turned on. When routing cables, you should always ensure that the current flows are balanced as much as possible. This can be difficult for central heating systems if the wiring's all over the place, but easy enough to do with lighting, provided you take care with any 3 way lighting to only feed at one end and don't loop neutrals separately from lives.
Christian.
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On Thu, 29 Jan 2004 16:13:32 -0000, "Christian McArdle"

It's not wrong, it is the same as running the lives from the rose to the switch, its just that this method bypasses the rose. If it was to be banned you would have to ban all types of 'unbalanced' cabling, e.g. singles, 3 phase and anything else that doesnt carry the same current on the neutral returned as the live feeding it. This would also include regular loop-in methods.
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No it isn't. In a loop in system, the power feeds are balanced. The switch drops are balanced. It is all balanced.

Indeed. In a domestic setting, unbalanced cabling is simply not required and will cause considerable distress and discomfort to hearing aid users.
In what way would 3 phase in one cable not be balanced? (Without tripping the RCD due to an earth fault). You don't even need a neutral to balance it, although if a neutral is used as a live conductor, it MUST also be present in the cable.
Singles, indeed, should be used with caution (i.e. only if T&E is not available for the cross sectional area) and routed adjacent with the other cables of the circuit to reduce imbalance. The closer the better, provided that cable grouping derating allows it.
Christian.
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On Thu, 29 Jan 2004 16:55:54 -0000, "Christian McArdle"

Actually, now I think about it...yes!

If a TP&N supply was feeding a DB that was feeding a mixture of balanced TP and SP loads the supply cable to the TP DB would be unbalanced between L1,L2,L3 & N.

No-one says the wiring methods adopted are perfect in all situations, that's why careful selection of the best method for the installation is required. In a domestic situation it is highly unlikely to have a induction loop system fitted. If you were going on the basis of making all homes 100% disability friendly you would have to get rid of all stairs, sharp corners, steps, visible only warnings etc... I think the term 'reasonable expectations' would apply to all installations.
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It will remain balanced, provided all live conductors (including any active neutral) go through the same cable.
Take a 3+E cable. Draw off red phase, you get current through the red and return current through the black. Balanced. You can do the same for any other phase.
You can draw current through multiple phases at the same time and it will remain balanced. As the phases are out of phase (strangely), the value of the current in the neutral doesn't just get bigger as you add current. Some of the red phase return path may go down the blue/yellow phase instead, for example.
Indeed, if you draw the same current through each phase, it still remains balanced, although the neutral current drops to zero! A 3 phase motor will typically not require the neutral as it draws equally from each phase.
In any case, I see no reason why the electrons going up the 4 conductors doesn't match the number of electrons coming back, unless they're falling out of the cable somewhere, or there is a separate conductive path, such as an earth fault or external neutral.
To be balanced DOESN'T require the same current in all the phase conductors, just the total current vector in all conductors to add to zero. If it didn't, a 4P RCD would trip!
Christian.
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On Thu, 29 Jan 2004 17:31:10 -0000, "Christian McArdle"

Hmmm... Anyway, I've never come across a problem with induction loops in a commercial property, wired in singles, twin or any other method. Nor have I even come across an induction loop in a house, I'm not saying none of the above happen but the likelihood... I'll leave that one to personal choice.
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Singles will OK, if run together. It is separation of the conductors that matters. Splitting phases doesn't matter if the only return path (i.e. the neutral) goes with it.
Christian.
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I can assure you it is not. Many hearing aid users have modified telephones, or induction loops for television watching within their homes. These devices are cheap and widely available.

Indeed. I think it is unreasonable to install an unbalanced lighting system that may have interference effects over a wide area, including your neighbour's property, who may not be able to use their telephone or watch TV and certainly are unable to go into your house to fix the circuit.
Christian.
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Much as I hate reading "me too"s, point seconded. All NHS-supplied and many private hearing aids have the ability to be switched to "loop" mode (usually a "T" position on an analogue aid). This can be a great help when listening to the telephone, and, as you say, "personal" loops are available for, for example, television watching.
One in seven of the population of Britain is medically classed as "deaf", though obviously the amount of loss varies considerably. That means that in my row of a dozen houses, at least one, and probably two of them will have a deaf person living there.

TBH I've found that the OSG's recommended two-way switching circuit is easier to understand and dead easy to install when compared with the older way of doing things. The switch nearest the lamp is wired in almost the normal way (permanent live goes in a different hole), and you run a three+E to the other switch(es).
Hwyl!
M.
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I'm 1/2 deaf.

It's all easy when you do it every day!
SJW A.C.S. Ltd.
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snipped-for-privacy@telling.you (Lurch) wrote:

I do! It's just that the "engineer" in me sees a greater beauty and symmetry in the method described in the OSG, just as it sees the same in the normal switch-drop method :-)
Given the low current usually involved in lighting the hall/stairs/landing though, and the distance of the circuit wires from the television (normally) I wonder just how much potential for interference there really is... but when the solution is so simple, it isn't worth not doing it, is it?
Hwyl!
M.
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On 29 Jan 2004 04:44:05 -0800, snipped-for-privacy@hotmail.com (Nick) wrote:

You don't get ring lighting circuits, except for some industrial situations. What you have is the neutral feeding all of the lighting points in a radial configuration. The lives loop around all of the switches in a radial configuration. Then from each switch a single live switch wire is taken to the light point. The three seperate wires in your switch, (assuming you have 1 light point in the room in question), would be - 2x live feed and 1x live switch wire. The last light on the circuit would have 1x neutral in the light point and 2x live in the switch, (1x feed and 1x switchwire).
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These any help:
http://www.dablighting.co.uk/lightwiring.html
http://www.diydata.com/planning/electric_lights/electric_lights.htm
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