Electric light switches

[markneedhelp]

we have two light switches in the living room one that controls the main living room light and one for the landing.

on the other side of the room (OPEN PLAN) there is another switch which also turns on the main living room light and one for a light above a table.

the switch i have taken of has L1 L2 common at the top
common L1 L2 at the bottom

there is a black/red wire at the top and
black/red wire at the bottom with a brown wire from common to common

This new fancy chrome one is

L1 L2 L3



L3 L2 L1

can someone give me an idea what goes where before i try a million combination and end up like a KFC

any help would be great

cheers mark

 

[andy]

depends on the switch, but id assume old com will be L1, old L1 will be L2 and old L2 will be L3. same for the other switch

 

[dingbat]

On the old switch 'Com' means common. Depending on the position the Com terminal will be electrically connected to either L1 or L2. On the new one it is almost certain that L1 is the common, which may be alternatively connected to either L2 or L3. If in doubt though, use a continuity tester to make absolutely sure.

In both cases you have two switches side-by-side but upside down relative to each other; that is, from your diagram the top left L1 switches to the bottom left L3 and L2, while the bottom right L1 switches to the top right L2 and L3. Normally there will be some other markings, such as a diagonal embossed line separating the two switches.

 

[MANDATE]

The way you view the switch you have taken out is incorrect.They are two serarate two way switches, each with three terminlals that form a triangle.
You view the switch terminals side by side, not top and bottom. I presume to save space one of the switches is inverted, so L1 and L2 at the top belongs to 'common' at the bottom and 'common' at the top belongs to L1 and L2 at the bottom.
A simple test using a meter will confirm if the new switch follows the same pattern. If L3 has taken the place of common then it follows the same pattern.
Two further bits of information. You can use a two way switch in a one way mode by using 'com' and 'L1' (or L2 if you like).
There are two different methods of wiring a pair of two way switches.
An older method uses 'live' to 'com' on switch A. Then 'switched live' to 'com' on switch B. the two switches are connected L1 to L1 and L2 to L2.
The later method uses 'live' to L1 and 'switched live' to L2 both to the same switch. The two switches are then connected using three wires instead of two. ie 'com' to 'com', 'L1' to 'L1' and 'L2' to 'L2' You need to establish which of these methods is in use.
Also remember to save running 2 long live wires to each switch in a gang it is sometimes taken to one switch only and then a short link to the adjacent switch.

 

[ban-all-sheds]

Also, if you'd had the sense to realise that a multimeter was just as essential for this job as the screwdriver you used to remove the old switch then you wouldn't be in this situation.