Replacing A Light Switch - Little Help Please

[RDD]

Hi all,

Yet another query about the random electrics I'm gradually finding in my house

I'm just coming to replace the light switch in the kitchen only to find that it has two red wires and one grey common going into it, I asked the electrician who installs the electrics at work and he suggested it may have been a two way room at some point, this makes sense as I believe it's been made open plan since meaning some wires may have been joined (?) and shoved into a wall somewhere.

The existing one doesn't have markings indicating what the top two red wires do, the bottom grey wire is marked COMMON, the 1 way switch I want to install is marked L1 and COM, would I be right in thinking

a) I could put both live wires into the L1 of this single switch and the grey into COM

b) put one wire into L1, but which one?

c) am I going to have to buy a 2 way switch for a 1 way room?

Many thanks for any help as always!

 

[Taylortwocities]

I'm not sure what you mean.
The existing switch, how many terminals are there, 2 or 3?

Where are the grey and two red wires connected to these terminals?

A photo would help.

If there are three separate wires into 3 separate holes in teh existing switch then you'll need a 2-way switch as there's no way of knowing what skullduggery may have been visited at the other end(s).

PICTURE please./
//www.diynot.com/forums/viewtopic.php?t=129539

PS there will be some marking on the old switch. have a good look.

 

[ban-all-sheds]

I'm just coming to replace the light switch in the kitchen ... the 1 way socket I want to install is marked L1 and COM

Socket:

Switch:

 

[RDD]

Thanks for getting back to me Taylortwocities.

The current switch is below, I've had an even closer look with an LED torch about an inch away and I still can't see any markings around the (what should be) top two inputs. All I can tell you is it's made by Tenby and it's been put in upside down!

Untitled

• RDD
• 24 Nov 2013
• 1

The switch I was hoping to use (we got a job lot for next to nothing)

Untitled

• RDD
• 24 Nov 2013
• 1

ban-all-sheds thanks for picking me up on my terminology in a couple of places, now edited.

 

[EFLImpudence]

You have bought the wrong switch.

You need a 'two-way' switch with three terminals.

 

[RDD]

You have bought the wrong switch.

You need a 'two-way' switch with three terminals.

As I say it's only one we had knocking around, I was trying to not have to buy another as from a usability perspective it's no longer a two way switch (the other end is nowhere to be seen).

 

[sparkwright]

The old switch is a one gang two way switch.

The new switch is a one gang one way switch.

The fool proof method would be to buy a new one gang two way switch, put the grey in the common terminal, and one one red in one remaining terminal, the other red in the remaining terminal.

However, since you reckon another switch in the room has been removed and the cable therefore capped off, using your new switch may work.

To do this, you need a connector block, as one red cable won't be required. The question is, which one?

Is it easier to obtain a connector block, or take the switch back, and get a one gang two way switch?

 

[maltaron]

Surely the other end of the two way setup must have one red and the common joined somewhere, if its been altered then that may be adjacent to the light fitting controlled by the switch. I would think that it is advisable to locate the point of connection before changing the switch (which could be a one way as long as you know what's happening at the other end)

 

[RDD]

The old switch is a one gang two way switch.

As one red cable won't be required. The question is, which one?

Is it easier to obtain a connector block, or take the switch back, and get a one gang two way switch?

I'm thinking from what everyone's said it's safer to just buy the correct switch, they're not expensive I was just hoping I could have used the one I have here, would this do the job then?

http://www.screwfix.com/p/mk-1-gang-2-way-10ax-light-switch-white/11822

 

[sparkwright]

That's him.

As said, it can be done with the other one you have, but will take a bit of testing first - so whatever you're comfortable with.

 

[PrenticeBoyofDerry]

If the switch only requires a one way function you do not need a two way switch.
Terminate the grey sheath cable to com, this is very likely to be permanent live, the two remaining cables are switch lives, one will operate the light, one will not as the two way function has been removed (maybe not safely but nevertheless) So this would be trail/error by means of trying one in L1 and seeing if the light comes on and goes off. If not try the other red
The spare red can then be safely terminated in to a connection strip, all on it's own.

 

[RDD]

If the switch only requires a one way function you do not need a two way switch.
Terminate the grey sheath cable to com, this is very likely to be permanent live, the two remaining cables are switch lives, one will operate the light, one will not as the two way function has been removed (maybe not safely but nevertheless) So this would be trail/error by means of trying one in L1 and seeing if the light comes on and goes off. If not try the other red
The spare red can then be safely terminated in to a connection strip, all on it's own.

This is more what I was thinking to be honest, it seems to make sense given the other end is taking care of itself (as you say hopefully it's been done well but who knows, it's now in a wall/ceiling cavity somewhere!).

I know you wouldn't have suggested it if you though it was possible but just to put my mind at rest, would it matter if I get the wrong live red at first?

 

[RDD]

That's him.

As said, it can be done with the other one you have, but will take a bit of testing first - so whatever you're comfortable with.

Many thanks, if it doesn't work out I'll go with this, as mentioned I can't really test it as I have no idea where the other end is

 

[PrenticeBoyofDerry]

I know you wouldn't have suggested it if you though it was possible but just to put my mind at rest, would it matter if I get the wrong live red at first?

Well if we take in to consideration, every time you switched the existing two way off, that would be the same as introducing the wrong red, you are not in any more danger than you were every time this light was off and by identify which ones is the functional switch live and terminating the spare from the switch, you would possibly be safer in that aspect.

 

[RDD]

I know you wouldn't have suggested it if you though it was possible but just to put my mind at rest, would it matter if I get the wrong live red at first?

Well if we take in to consideration, every time you switched the existing two way off, that would be the same as introducing the wrong red, you are not in any more danger than you were every time this light was off and by identify which ones is the functional switch live and terminating the spare from the switch, you would possibly be safer in that aspect.

That's great, many thanks, hopefully this will save me some money too which ultimately is what DIY is all about

Just as a follow up in case anyone has a similar problem this worked a treat and was the first red wire I tried.