How do I wire a dimmer switch correctly.

Having tried to wire in a new dimmer switch and managing to blow the entire switch unit! I am seeking advice from anyone who is competant at doing this. I include all possible details below.

The Room Setup: One single switch feeding 3 wall lights, nothing complicated.

The existing switch wiring: When I remove the case I have, two black wires (neutral) wired together to form a circuit. Two earth wires fed into the metal backplate. And two red wires (live) each feeding into different holes on the back of the switch itself, to form the switched circuit.

The NEW Dimmer: Has 3 sockets on the back, marked up as L1, L2, and earth symbol.

I thought the obvious thing to do was to wire one of the live wires into L1 and the other lived wire into L2. I then wired the existing earth leads into the ground socket. I took the earth strap from the new metal dimmer switch and wired that to the back plate ground point. When I turned on the power it blew the brand new dimmer to smither-reans. What did I do wrong???

The new dimmer is probably sensitive to the live wires being the right way around. I would guess that L1 should go to the permanent live supply, and L2 to the lights.

Check this with the dimmer instructions.

If you get it wrong you would most likely burn up the electronics in the dimmer.

Also, where did you join the neutral (black) wires in the new dimmer???

Im not an electrician, just a DIYer but...

The third hole on the back of your dimmer isnt an earth terminal, its the common. The L2 is only for wiring up a 2 way circuit i.e 2 switches so dont use that.

Normally there would only be a black and red wire.. the fact you have two red and two black suggests the blacks arent being used. Thats why they werent connected to the original switch.

One of the red wires comes from the mains, the other goes out to your lights. The mains red should be connected to the comkon terminal, the other red wire to the L1 terminal.

You need to work out which is which. With non of the wires connected to the switch, only one of the red wires should be live. Thats your mains wire.. connect it to the common, and the other to the L1.

The earths should be connected to the backbox as they originally were. If your dimmer has a metal front plate then you also need to earth this. There should be an earth terminal on the back of the metal ( not on the plastic box with the L1/L2/Common holes ). Use a short piece of insulated wire to connect this earth terminal to the backbox at the same point as the earth wires.

If its plastic, just earth the backbox.

about the blacks is not stritly true, if the feed (live and neutral) comes into the switch first (it should not but can be done this way)then the two blacks (neutrals) should be connected together and the switch shoud "break" the red (live)