Dimmer Switch Wiring

Lennys_Shinpad

Hi, I ordered a double dimmer switch but it didn't come with instructions. Can anyone tell me how best to wire it up?
Here is a photo of the wiring on the current standard double switch.

As you can see, the two live wires go into the 'L1' parts of each socket with a brown wire connecting each 'L' part.
The dimmer switch (below) has parts called L1, L2 and Com. I was planning on connecting the two brown wires to the L1 parts and leaving the Com part alone. From looking online, it looks like Com is used when you have two separate switches for a single light. The thing is, if I ignore the Com part, then do I still need a brown cable between the two switches as was the case for the standard switch in the original photo?
Thanks in advance.

fenwick458

Old switch ------- New switch
L             --------- COM (so you'll still need the link from COM to COM on the new switch)
L1            ---------L1
L2 is not used 

Lennys_Shinpad

fenwick458 said:

Old switch ------- New switch
L             --------- COM (so you'll still need the link from COM to COM on the new switch)
L1            ---------L1
L2 is not used 

Excellent thanks.

Lennys_Shinpad

One final thing, there are three live wires. Original, two of them went into the L1 parts and one went into a 'L' part.
I am assuming that the spare live cable should go into the COM part of the new switch. Is this right? If so, does it matter which COM part (there are two)?
Thanks.

fenwick458

you're overthinking this. 
L             --------- COM
L1            ---------L1
thats all you need to do

Lennys_Shinpad

Sorry, just to be doubly sure before I switch the light back on, here is a photo of how I have wired up the new switch. Is it correct?
For the three live wires from the wall, one goes to COM and the other two go to the L1s. There is then a brown cable between the two COMs.
Cheers.

Mutton_Geoff

That looks fine. If your light fittings are LEDs, you might find them difficult to control unless that dimmer is designed for LED (ie leading trailing edge dimming), but you can do no harm in just trying. The usual effect of the wrong dimmer is not being able to dim below 50% or when you press to turn off at a dimmed level, pressing again does not restart the LED, the brightness needs to be turned up and back down again when the light has "struck".

Edited as I got my leading and trailings mixed up

Lennys_Shinpad

Thanks Geoff. It is for LED so might have bought the wrong type. Will soon find out.

Belenus

Mutton_Geoff said:

That looks fine. If your light fittings are LEDs, you might find them difficult to control unless that dimmer is designed for LED (ie leading edge dimming), but you can do no harm in just trying. The usual effect of the wrong dimmer is not being able to dim below 50% or when you press to turn off at a dimmed level, pressing again does not restart the LED, the brightness needs to be turned up and back down again when the light has "struck".

Did you mean trailing edge dimming? LEDs usually require trailing edge dimmers.

Lennys_Shinpad

It's buzzing. Will buy a proper LED one and get that fitted.

Belenus

Lennys_Shinpad said:

Thanks Geoff. It is for LED so might have bought the wrong type. Will soon find out.

I think you have. Your new dimmer has a watt range of 40 to 500 which is typical of a leading edge dimmer for traditional incandescent lights.

The Varilight trailing edge dimmers I have bought for LEDs have a range of 10 to 100 watts.

Useful link.