Help with connecting my dimmer switch

[kenny67]

Hi there,
I hope someone out there can help me.

I thought I would install a dimmer switch in my daughter's bedroom as I have just finished of decorating it and that would finish it of.
I assumed wiring a dimmer switch would be straight forward even for a novice like me, just follow the wires no problem.
I bought a dimmer switch from homebase and was ready to go.
When I unscrewed the light switch from the wall and seen all the wires I just gave up.

The house is around 30 years old and the electrics are in good condition as I was informed by a spark whom I trust.

This is what is inside the box behind the lightswitch.
Firstly there are 3 grey cables in each of these cables there is a red live and a black neutral wires.There are also the 3 green/yellow wires that that come from the bottom of the box and feed into each of the 3 grey cables.

2 of the red wires are connected to the available screw at the top on the back of the existing light switch and the other is screwed into the bottom of it.

The 3 black wires are capped and do not connect to anything.
I have looked at the back of other light sockets and they are all the same

What I'm not sure of is which of the 3 red wires go into the com and L1 on my dimmer switch ?
I hope my explanation is understood as I lack of electrical description.
Many Thanks

[jason123]

Whatever connects to the existing switch has to connect to the dimmer. If you start connected reds and blacks that werent previously connected things start to go pop.

Read the leccys tips and you will get a good explanation of what all the wires do.

[kenny67]

Cheers Jason 123,
My other concern was that there were 2 red live wires connected to the screw at the top of the original lightswitch though the other lightswitches are wired the same, I take it that must be ok to do so ?

[sparkydude]

Yes thats fine, all you have is whats known as a loop in system , but instead of using a ceiling rose they run the feeds and the load to the light to the switch box instead of the rose. The three blacks that are capped off in connecter are your neutral in ,neutral out , and neutral to your light fitting, the two reds in the top are live in and live out, and the live on its own is the switched live to your light fitting.

Hope that clarifies your situation

Nick

[Rich-Ando]

the black wires in a switch are "switched lives" they are not neutrals.

if your house wiring is 30 years old you have the old method of lives being looped to the switches.

without looking ta it i can pretty much say..

all the red cables (live in & two lives out it appears) should connect to C

the black cable connects to L1

[Rich-Ando]

lol replying at the same time

[sparkydude]

DO NOT DO AS RICH ANDO SAYS

they are not as he says , the blacks ARE NOT SWITCHED LIVES they are NEUTRALS if connected as he has stated then you will get a small explosion and blow your fuse/MCB out.


Nick

[Rich-Ando]

my appologies, i didnt actually read it properly

i saw the usual dimmer switch question and just assumed..

This is what is inside the box behind the lightswitch.
Firstly there are 3 grey cables in each of these cables there is a red live and a black neutral wires.There are also the 3 green/yellow wires that that come from the bottom of the box and feed into each of the 3 grey cables.

as u know full well, people assume black wires in a switch are neutrals. apart from which, there should never be neutral wires in a switch.

sorry for that, i will make sure i read fully next time.

[kenny67]

Hey
Thanks very much for clearing up my dimmer switch issue it's much appreciated.
Cheers