wiring two gang two way light switch

I am trying to replace two light switches for dimmers.

Both switches are two way.

One of the switches has three wires and the other has two.

Each of the wires have three inner wires (excluding the bare earth) and they are coloured black, grey and brown. One of the main wires (the 3 wire box) has 'switched feed' written on it. All the other wires are unmarked.

The dimmer switch I have bought (which i intend to fit onto the box which has three wires coming from it) has two L1 terimnals, two L2 terminals and two which have a symbol that looks like a wavy line with an arrow going through it.

So, in summary I have the following.

Box 1 (excluding earth).

3 black wires 3 grey wire 3 brown wires

Box 2 (excluding earth):

2 black wire 2 grey wires 2 brown wires

Switch 1 (for box 1)

2 L1 terminals 2 L2 terminals 2 wavy line terminals

Switch 2 (for box 2)

2 L1 terminals 2 L2 terminals 2 COM terminals

Can anyone tell me how to wire these switches?

Many thanks, Alex

Reply to
alex6192
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On Thu, 18 Dec 2008 16:32:38 +0000 someone who may be alex6192 wrote this:-

Are the switches side by side, or in separate locations?

What is marked on the terminals into which these wires are connected? If you can't pull the switches out to look with the wires connected then undo one terminal at a time and mark which wires went into that one, then when you have the switch off see what the markings are.

Reply to
David Hansen

The switches are in seperate locations. Both are two gang and both are two-way. The switches control two banks of spot lights in the lougne (4 spot lights each). The box which has three wires (3 3 core wires) is in one location and the box which has two wires (2 3 core wires) is in another location.

Studily I didn't mark which wires went where when taking off the old switches. btw the new switches are dimmers.

Reply to
alex6192

On Fri, 19 Dec 2008 10:46:36 +0000 someone who may be alex6192 wrote this:-

Let me see if I have this right. All the switches are in the lounge. In one box there are two switches (mounted in the one plate), one of which controls half the spot lights and the other switch controls the other half. In another part of the lounge there is another box, which also contains two switches which also control the spotlights. The spotlights are not controlled from another location as well. One of the boxes has two three core + earth cables, the other has three of these cables entering it.

If that is the case then this is what I think you have:

1) the box with three cables has one cable which contains the permanent live and two switched lives to the groups of spotlights. 2) the same box has two three core cables which go to the other box, each of which provides two way switching functions for one group of spotlights. 3) the box with two cables coming in has the other end of these two way switching cables.

To test this I would do the following, but only do this if you are confident you can do it without too much danger:

1) separate out the ends of all the cables until all are easy to test but not too close together. 2) turn on the electricity. 3) using a meter (or neon screwdiver if a meter not available and desperate) identify which of the cores is the permanent live. Only one core should be live, test them all to make sure. 4) turn off the electricity. 5) mark the permanent live, permanently. 6) using a terminal block connect the permanent live to one of the other cores in the same cable (obviously not the protective conductor). 7) turn on the electricity. One group of spotlights should light up. 8) turn off the electricity. Mark what that core feeds, permanently. 9) move the terminal block to connect the permanent live to the other core in the cable instead. 10) turn on the electricity. The other group of spotlights should light up. If it does you are almost there. 11) turn off the electricity. Mark what that core feeds, permanently. 12) at this point if you have a meter make a flying lead and use this to work out which ends of the other cables is which. To do this connect the flying lead to say the brown of one cable, go to the other box and test both browns. The one with zero resistance is the other end. Mark both ends of both cables, A or B is preferable to 1 or 2. 13) you now have enough information to wire up the switches. If you think you don't think about it yourself for a while and draw some diagrams. and the like explain how two way switching works, but remember that in this case instead of a two core and earth cable coming in there is a three core and earth cable because you have two groups of spotlights. As you have marked the switched lives to the spotlights you should find that the switches on the box with three cables control the right set of spotlights. 14) if you didn't have a meter at 12) then connect the switches up. If you are lucky then you won't have to do anything else. If you are unlucky you will find that the switches on the box with two cables control the wrong set of lights. If that is the case swap the cables over.

Most of us have regretted doing that.

With "normal" dimmers only one dimmer is installed per group of lamps. The switch with the dimmer turns the lights on and off and controls the brightness of the lamps. Other switch positions simply turn the lamps on and off. Even if the dimmer is turned right down the lamps should glow enough when switched from another location to be able to walk to the dimmer and adjust the brightness.

Dimmers take more space than a "normal" switch. Therefore I would consider the box with two cables to be the favourite location for the dimmers. I would place it there unless that did not find favour with "the domestic authorities" in which case a deeper box may be necessary at the location with three cables. The disruption this will entail (assuming the walls are not plasterboard) may be enough to convince "the domestic authorities" to change her mind.

Reply to
David Hansen

Make those cables. And the inner 'wires' are normally called cores.

Strange. You're describing a two way switch circuit by the three core cable - but the 'switched feed' is normally two core. 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

I've never seen one like that - what make is it? Most have three terminals for two way switching marked Com, L1, l2.

It looks to me that the existing switches are intermediates. These have four terminals as opposed to three. As per the diagram above. If that's the case the switch part of the dimmer will also have to be an intermediate - and I've not come across one that is.

I'd also guess there were choc block connectors inside the boxes which you've omitted to mention.

Reply to
Dave Plowman (News)

On Sat, 20 Dec 2008 12:28:06 +0000 (GMT) someone who may be "Dave Plowman (News)" wrote this:-

According to the OP it is a two gang dimmer. The wavy line, which is presumably to indicate variable light output, is undoubtedly the same as the Com terminal.

Reply to
David Hansen

A lot of dimmer switches use this labelling method. The "wavy line" terminal is the Com. It is supposed to represent a dimmed connection to terminals L1 and L2

I do not think so. I think there is a link wire that the OP did not mention between L1 and L1. There are many ways of wiring things this up. This is probably the best option, and I suspect a junction box is involved somewhere.

If you double your picture up so that it shows a two gang two way set up and a link wire that joins L1 to L1 (not shown)

L1 L1 0===========0 0===========0=============Link to line | | C 0================================O C \ / 0===========0 0===========0============= Bank 1 lights== L2 L2

L1 L1 0===========0 0===========0============= Line====== | | C 0================================O C \ / 0===========0 0===========0============= Bank 2 Lights= L2 L2

Then the 3 core and earth cable labelled "switched feed" is the cable to the right of the picture (Line, bank 1 lights and bank 2 lights). The OP needs to identify the permanent live from this cable(most probably the brown), then the other two cores are the outputs for banks 1 and 2 of the lighting circuits.

Adam

Reply to
ARWadsworth

The ASCII art did not work. Try

L1 L1 0=============================0 Link to line below | C 0==============================O C \ 0============================0========== Bank 1 lights== L2 L2

L1 L1 0===========================0======= Line====== | C 0================================O C \ 0============================0========= Bank 2 Lights== L2 L2

Adam

Reply to
ARWadsworth

On Sat, 20 Dec 2008 15:20:49 GMT someone who may be "ARWadsworth" wrote this:-

I think so too and this has been lost.

Reply to
David Hansen

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