New Dimmer Switch Install, existing switch has 2 red wires..

[woody190881]

Hello,

First time poster here so go easy

In our living room the main light can be turned off from 2 different switches. The first is a single switch as you enter the room. The second is at the bottom of the stairs and is next to 2 other switches (one for the upstairs landing and the other for the outside light).

I want to change the single switch as you enter the room to a dimmer.

When i unscrewed the existing normal switch, there are 2 red wires and 1 black wire. 1 Red go's to a terminal at the top on its own and the other red go's into a terminal at the bottom next to the terminal where the black is.

I know the black is the neutral but how do i know which of the reds is the "live"?

The new dimmer has an L1, L2 and a squiggly line terminals.

Any help would be appreciated

 

[Aragorn84]

The old switch should be marked up with L1 L2 and COM?

 

[woody190881]

The old switch should be marked up with L1 L2 and COM?

Its a very old switch but ill take it off again and have another look. I dont think it had any markings though, it was a plain piece of green plastic. Ill double check though.

 

[ban-all-sheds]

I know the black is the neutral

No it is not!

That you think it is shows that you don't understand how lighting circuits work, and that you think a neutral could go into a switch with lives as you describe shows that you don't know what switches do.

Please put doing this work on hold until you've learned how it all works - fiddling with lighting circuits with the belief that if it's black it is a neutral will end in blown fuses, damaged switches, and excitement of the wrong sort.

• http://www.google.co.uk/search?q=electrical+circuits+101
  
  
• http://kevinboone.net/electricity.html
  
  
• http://web.archive.org/web/20080213151445/http://www.kevinboone.com/domesticinstallations.html
  
  
• //www.diynot.com/wiki/electrics:lighting
  
  

 

[canduit]

I know the black is the neutral

As BAN says, its not neutral. All 3 are line and will carry 230 volts depending on the switch position(s). The black wire should have a bit of red tape round the end to signify this. The reason for this? Cable with 3 red cores and an earth is not readily available. Hope that helps.

 

[woody190881]

Thanks for the replies.

BAN - i take your advice on board and will make sure i have a good read. Im wanting to learn but at the same time dont want to risk myself or anyone else.

I cant check out behind the current switch until the weekend as i dont get home while dark. Hopefully it will have markings as Aragorn questioned then the changeover is like for like.

 

[ban-all-sheds]

I cant check out behind the current switch until the weekend as i dont get home while dark.

[OFF TOPIC]

My wife was telling me something she heard about recently at a lecture on the origins and history of the English language, about the use of the word "while" in some places to mean "until". There were unmanned level crossings with signs saying "Please wait while lights are flashing", and some people were killed because they waited until the lights started to flash before they crossed.

[/OFF TOPIC]

 

[woody190881]

I cant check out behind the current switch until the weekend as i dont get home while dark.

[OFF TOPIC]

My wife was telling me something she heard about recently at a lecture on the origins and history of the English language, about the use of the word "while" in some places to mean "until". There were unmanned level crossings with signs saying "Please wait while lights are flashing", and some people were killed because they waited until the lights started to flash before they crossed.

[/OFF TOPIC]

It could be worse, i cud use txt spk!