2-gang dimmer bodge?

[David Fisher]

I've been trying to replace a 2-gang dimmer inherited in our living room with a new switch. The exisiting wiring is shown below (hopefully), with what appears to be a bodge by connecting the live from the first gang to the load terminal of the 2nd one (I guess they didn't have a spare piece of wire to connect it to the live terminal!).

Every switch I've tried using, however, (about 3 different ones) whether I connect the live feed to live terminals on both gangs or I replicate the current setup, I cannot seem to get the lights to switch on (or, in one instance, one circuit remains on regardless of the switch positions). I have ensured that all the switches have the necessary load capacity (4x60W incandescents).

Any thoughts?

Live feed

---------------- ------------- -------------------------- ¦ ¦ ¦ ¦ Live XX XX Load

Load XX XX Live ¦ ¦ ¦ ¦ ¦ ¦ Light 1 Light 2

[Lurch]

Sounds like you've got your feeds and switch wires mixed up. Get your tester out and find the feed first then try again.

SJW A.C.S. Ltd.

[N. Thornton]

it makes no difference.

I agree with the other reply, youve mixed your wires up. If you can test it safely while powered up, the live feed will be live, the 2 wires off to the lights wont be. If you arent able to do this safely, dont.

I suggest you dont touch it, switch off house power, vacate the house, and call as many experts in to rectify it as possible.

Regards, NT

[BigWallop]

The configuration of a two gang, two way switch plate, which it sounds as though you're trying to install, will have two COM terminals, one on each switch, two L1 terminals, one on each switch, and two L2 terminals, one on each switch.

The live feed from the fuse box (consumer unit) will be connected, in your case, to both COM terminals on each switch by the use of a red (if possible) link cable between them. This gives power (live) to both switches. The switch wires, the ones that go from the switches and on to the lamp fittings, would be connected to each of the L1 terminals on the switches. It is that simple.

If you have any more cables to the switch back box, then you've really got a bodge on your hands, or the neutral cables have also been taken to the back of the switches.

[Lurch]

Having more than 3 cables in a box is not a bodge, connecting them up wrong or unsafely is.

SJW A.C.S. Ltd.

[David Fisher]

Thanks for the suggestons, but the number of cables, and connecting live to load between switches are not the problem.

I've tested it and tested it, and the live is definitely the live. I know that running live into switch 1 and feeding from there into load on the next will work - indeed it works fine on the currently installed switch. As I mentioned originally, I believe they only did this as they didn't have a long-enough piece of wire to connect it to the live on switch 2 (the switches are mounted in the opposite way to each other).

The loads are definitely running to the correct light circuits. If I bypass the switch completely, then I can turn each circuit on and off by manually connecting and disconnecting the wires.

What I don't get is why I cannot install a different switch, and have tried with 3 different ones, and get the lights to work (regardless of which cables I have connected to live and load on the second switch.

[Dave Plowman]

It looks like by your diagram you've got two way switches used as one way

- not unusual, as I don't think they do 2 gang one way.

The only possible answer is that you've connected in and out to the L2 and L2 terminals, instead of using the common for either.

I presume your switch is marked 'com' 'L1' and 'L2' ?

I've tried to give the normal layout below. Each set of terminals form a triangle.

com\ L1 L2 O \ O O \ \ O O \ O L1 L2 \ com

To clarify, you *must* use the 'com' terminal on each switch, or it won't work. But it doesn't matter whether it's used for feed or load. You can use either the L1 or L2 for the other connection, but best to use the same configuration on both switches or you'll end up with one up for on and one down. ;-)

[Lurch]

Just to clarify, you do have only three cables in the back of the switch don't you?

SJW A.C.S. Ltd.

[copey]

what switch 's are you trying to use ???

[David Fisher]

.

Thanks for the responses. To clarify:

The switches are, unusually, 1-way rotary dimmers, so there are only COM and L1 connections.

There are two 3-core cables in the back of the switch. One has the red cable connected to COM on switch 1 and the black to L1, providing load to circuit

1. There is a separate piece of cable (sheathed in brown) connecting COM from switch 1 to L1 on switch 2. The second cable has red connected to L1 on switch 2 (providing the onward ring), and black connected to COM on switch 2, as the load to circuit 2. Both cables have earth (correctly sheathed) to the back box, and the switch plate itself is earthed to these.

As for manufacturers, there are no discernible markings on the switch which is in there and working, but it will be at least 10-years old. The switches I have tried are Homebase's own brand dual push/rotary 2-way, 2-gang dimmer, and a touch dimmer (flat plate, split in two), again 2-way, 2-gang (not sure of the manufacturer, as I'm in work now and the switch is in my garage, 70 miles away!).

I have received this morning a 400W 2-way, 2-gang touch/remote Varilight dimmer, which I'll give a go over teh next couple of days and report back. In the meantime, if you have any other suggestions, they'll be gratefully received.

Cheers

Dave

[Dave Plowman]

Not unusual. A rotary switch means the dimmer is on minimum when switched off, so two way switching might well be pointless. The push on/off types are usually two way as they can be left at any position.

[Lurch]

So, have you tested which one is the feed? Have you tried with normal switches? If what you say is correct I can't see what's gone wrong. Test for the live feed, connect this to each wire in the switch one at a time, with a connector, and turn on the power, note what comes on and lable the cables. From what you say the following should happen- When the feed is connected to the switch wires, (obviously this will happen twice), the light will come on but some other lights on the circuit will be inoperative. When the feed is connected to the ongoing feed, (it's doubtful to be a ring but a radial), the other inoperative light will come on but neither of the lights will. If all of the above happens then connect the live feed and ongoing feed to the com terminals of both switches with a link between. Connect the two switch wires to the two L1 terminals. Sit back and enjoy the tranquil moods obtained! If anything else happens other than the above let us know _exactly_ what does.

SJW A.C.S. Ltd.

[David Fisher]

Well, hooked up the Varilight switch, with cables in the expected terminals, tried turning it on and, guess what? Everything worked as it was supposed to.

Which leaves me none the wiser as to what happened with the other switches I tried. I suppose that I must have had sevearl faulty ones. I'll put it down to experience...

Thanks for the advice.