Hall & landing light switch puzzle


In my house, I have ceiling lights in the hall and landing. I have removed the 2 switches because they were connected as 1-way switches and I want to set up 2-way switching.
I think the necessary cables are already in place, because there are two T&E cables protruding from the wall in both the hall and the landing. But I'm not sure how to connect the switches such that the 2-way switching will occur. I have identified the T&E cable that acts as a normal switch for the landing light when the red and black are touched together, and I have identified the one in the hall that does the same for the hall light. For clarity, let's refer to these below as the "1-way cables".
I can't figure out how the other T&E cable should be used. I assume (though I'm not sure) that it goes from the landing light switch location down to the hall light switch location. I can't think why else there would be an extra cable protruding at each location.
My volt meter reads no voltage across the red + black of the extra cable protruding from the hall wall. Nor for the extra T&E protruding from the landing wall (possibly the same cable).
So I thought I could try using either the red or the black to connect the 'common' terminals on each 2-way switch, and connect the red and the black of each "1-way cable" to L1 and L2, on its respective switch. But that didn't work.
Can anyone provide a link to a likely wiring diagram I can try using - or simply explain, in words, how I should connect the 2 T&E cables at each switch?
Many thanks,
Jak
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Jak wrote:

OK do you want to:
a) Be able to switch the landing light from the hall b) Be able to switch the hall from the landing c) both of the above

Your basic problem is you don't have enough wires. To achieve a or b, you would need a three core and earth running between the light switches. To achive c you need two three core and earth wires.

And if you twist em together on the landing and measure the resistance between them in the hall you will see if they are in fact the same cable.

Because you need another two wires. See the circuit here:
http://www.diyfaq.org.uk/electrical/electrical.html#two-way

See above

With what you have you are probably stuck. You could achieve a or b by being exceedingly naughty and using the earth wire in you link cable as you third wire (suitably sleeved of course). However I would strongly suggest that not a good thing to do for all sorts of reasons.
Any chance you could get an extra cable or two between the switches?
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Cheers,

John.

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On Thu, 17 May 2007 15:41:28 +0100, John Rumm

Thanks for the help. What I am hoping for is: d) The hall switch will switch the hall light and the landing light on and off together simultaneously. Likewise with the landing switch.
[part snipped]

How about my (d) above?

I should have thought of that!

Yes, it is feasable, but am still hoping I can achieve somthing with the existing cables. I guess something must be achievable, or why would the extra T&E have been put there?
If not, I may just use a PIR switch for the hall light - if I can find one for a reasonable price.
Jak
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Jak wrote:

Now there was me thinking I had all possible bases covered! ;-)
d equates to to either a or b with the added complication that you want to extend the switched live from whichever switch you choose to the other light.
However there is a e) of sorts. Assuming your extra wire does connect the two switches, you could use the two available wires to carry the switched output from one 1 way switch to the switched live of the other. This would achieve the functionality you describe in the sense that either switch would turn on both lights. However The only way to turn the lights off would be to have *both* switches off. (in engineering terms you have "wire or'ed" the lights together. (this is also bad practice since you would probably be driving one light with a live from one circuit, and a neutral for another.

You may discover these cables are not even related!

Don't get the type that installs in the light switch position - these have a number of issues that can come and bite you!
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John.

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On Thu, 17 May 2007 17:55:12 +0100, John Rumm

It does seem to be the same cable: I twisted the red and black together on the landing and found there was very little resistance registering between the red and black in the hall. Any idea what the purpose of this extra cable going from switch to switch might have been?

In what way? I have used a few of these in the past. I used to be able to get them for about £20 each, and they would typically last about three years before they started misbehaving (flickering lights, etc.) Nowadays, the only ones I see advertised seem to be around £50!
Jak
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Jak wrote:

Hard to tell. It might be there is another extra wire installed at the ceiling roses perhaps. This may make 2 way switching possible. If not then your guess is a good as mine.

The main trouble with running electronic widgets at a light switch position is the lack of a neutral connection. Hence most of these work by passing a very small current through the bulb even when off so as to power themselves. The situation gets tricky when the bulb gets replaced with a low energy bulb, and it all ceases working.
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You will achieve that with c above, you just have to flip two switches at once, that is how ours is wired. Whoever did it was very logical. Whichever switch set you are standing at, the closest switch operates the closest light etc (the switch by the front door also does the outside light, its first as when you are standing there it is just on the other side of the door). I have pointed out this elegant and logical system to SWMBO but it eludes her, and she has one degree in Maths and another in Computer Science....
Peter
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On Thu, 17 May 2007 15:41:28 +0100, John Rumm

Depends, if the upstairs and downstairs lights are on the same circuit then the T&E can be utilised to provide 2 way switching.
I'll not go into explaining it all though until the OP says yay or nay.
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Stuart.
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On Fri, 18 May 2007 02:31:57 +0100, Lurch

Yes! The two lights are indeed on the same circuit. I eagerly await your explanation of how to connect my two switches using the two T&E cables available at each switch! TIA....
Jak
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Ok then. The usual thing to do is switch the landing on and off from the hall, so we'll do that.
At the landing switch the live feed is unused, make it safe. The switch wire back to the light goes to the common terminal on a 2 way switch. The L1 and L2 terminals have the T&E that goes downstairs connecting to them.
At the hall switch the other end of this T&E goes to L1 & L2 on one side of a 2 gang switch. The 2 common terminals are linked together and one of them also has the live feed from the hall light connected to it. The last cable is the switch wire for the hall light, and this goes to L1 on the second gang of the 2 gang switch.
You should now have 2 switches in the hall, 1 for the hall light and 1 for the landing light, which will be a 2 way to the upstairs switch.
I'd ensure that this cable running from downstairs to upstairs actually is safe as it may have been disconnected previously due to a fault or damage.
--
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Stuart.
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On Fri, 18 May 2007 12:14:27 +0100, Lurch

IT WORKS!! Thanks a million for that, Stuart! And also for the clear instructions. I could never have figured that one out on my own!
The only way I deviated from the layout was that I ended up putting the dual gang switch on the landing and the single in the hall. It seems to work out perfectly for my purposes that way. That way, I can turn the light on in the hall when I come home at night, go straight upstairs and switch the hall light off from the landing. I found that couldn't be done with the dual gang in the hall and a single upstairs.
Regards,
Jak
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Good stuff, glad I've been of some use to someone somewhere this Month.
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Novel. If you look at it from the other way around you come in, switch the hall light on then when you're on your way upstairs you stick the landing light on and turn the hall light off. The landing light lights up the stairs and landing. Still works the same, it's a 60W lamp at one end or the other of the stairs at the end of the day.
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Jak wrote:

Might have simplified matters if you mentioned that earlier! ;-)
(cue, slaps head - should have asked this sooner. Well spotted Lurch!)

Have a look at:
http://wiki.diyfaq.org.uk/index.php?title=2_Way_Switching
In particular see the "alternative" circuit and then read the final note on the page. If both your lights are on the same circuit then you don't need the separate wire to return the com connection on the far switch and hence in this case you *do* have enough wires between the switches (to achieve a or b from my original list)
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John.

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On Fri, 18 May 2007 14:18:37 +0100, John Rumm

Yes - Thanks for pointing out the final note on the page. If I notice any interference problems with electronic devices, I will flip the MCB on the lighting circuit and see if it stops.
Jak
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Jak wrote:

You are fairly unlikely to get any interference problems in a domestic environment, so I would not worry about it.
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John.

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Starting out with the switch pair at the switch - as normal - you need three wires plus earth to provide a two (or more) way circuit. So if you have two circuits and only two spare TW&E running between them you can't safely change them both to two way switching.
Here's the diagram:-
L1 L1 0===========0 0===========0============= Line | \ / | C 0================================O C \ / \ / 0===========0 0===========0============= Switch return L2 Optional L2 Intermediate
If both lights are on the same circuit from the CU you could share the line in, but that only brings the total of conductors needed (excluding earths) down from 6 to 5.
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On Thu, 17 May 2007 18:58:00 +0100, "Dave Plowman (News)"

Thanks for the diagram. I'm a bit confused because your diagram only uses three wires (not including earth). So why do I need 5? (Yes, my two lights are on the same circuit from the CU.)
The electrician who rewired the house (over a decade ago) installed that T&E going from one switch to the other. What would it's purpose have been been?
Jak
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I'm assuming they are two lights with two switches as that's what your first post said. But if only one switch is to be made two way and you've two TW&E cables spare you're ok.

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Jak wrote:

It uses five if you count them right ;-)
The wire connecting Line to L1 and Switch return to L2 are two wires in the cable that connects a ordinary switch to the ceiling rose.
the three wires connecting L1 to L1, COM to COM, and L2 to L2 are usually a 3&E cable that runs between the switches.

Since it is not used, it sounds like he could not work it out either!
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John.

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