Please could I get some advice on this light switch wiring

[sololite]

Hi there,

I've just come to replace a light switch at my dad's place with a mechanical light timer, something I've done a couple of times at my own place but am confused by the wiring.

My Greenbrook timer needs:

1. Neutral from mains and Neutral to appliance
2. Live in from mains
3. Live output to appliance

the current light switch is only using red wires and hasn't been tagged. See attached image.

I'd be grateful if anyone can help me understand what the two red wires at the top are, do I need to be getting another wire from the circuit into play?

regards,

Chris

 

[terryplumb]

Do you have any testing equipment ?
The switch has two conductors ,probably permanent live ,in one terminal. The other conductor being the switched live. No neutrals in pic.

 

[333rocky333]

Most likely its a Live in and a Live out to the next room switch, you dont have a Neutral there so you cannot use your switch (Unless there is more Black wires tucked inside the box)

They usually make a version that does NOT need a neutral but they are usually unreliable depending on the type of lamp load.
A mechanical timer is usually what it says, so why does yours need a Neutral

 

[DetlefSchmitz]

This situation is very common. The traditional wiring at a light switch is Live and Switched Live. No Neutral.

To use a time switch (which almost always require a neutral so that the timer can be powered) you need to get the appropriate neutral from somewhere. This is not trivial if the cable to the switch is plastered into the wall. It's easier if the switch wiring is in conduit, but that's relatively unusual.

 

[sololite]

Thanks for all your replies. I do see black wires behind the switch. I think I'll draw a nice diagram to understand what I am seeing and then if I really understand it, I'll have a go.

 

[sololite]

I've uploaded a pic of the back of the switch now. I am guessing I can run a wire into that connector block where the black wires are joined to give me my neutral. I am also guessing that the single red into L1 is the switched live that goes to the light fitting. does that sound right? Hopefully the outside light coming on will deter the scum who tried to break in a few weeks ago. Thanks for all your help.

 

[DetlefSchmitz]

It looks promising. You should not guess about things like this. At the least, use a multimeter to measure the ac voltage between the blacks and the single red, with the switch in both positions. If you see about 240V in both positions, you should be ok.

 

[EFLImpudence]

It could be the two reds if looped at the switch.

 

[DetlefSchmitz]

True. Hopefully a meter will find this out.