lighting probs Ask questions and find answers to many subjects relating to electrics and electrical work

[chris _uk]

I have 2 way swiches in hall .I would like to install 1 dimmer and leave the other switch as is ....Trouble is on the original wiring in switch .. all red colours with 2 into com .. 1 into L2 and 1 into L3 .... i have a 2 way dimmer with only L1 and L2 connections .Can any one help .

Kind reegards chris

[kbrownie]

Hi Chris,
Rotary on/off dimmers are only suitable for 1-way circuits. If you have a 2-way circuit, You must install a push-on/push-off dimmer and replace one of the switches with that dimmer. You can only use one push-on/push-off dimmer in a 2-way circuit. It must be used with a normal switch as your second switch. When you switch on a push-on/off dimmer the lights will come on at the same level they were at before they were last switched off. Push-on/off dimmers can also be used in 1-way circuits.
Hope this is of help
KB

[chris _uk]

Hmm

the dimmers are touch dimmers one touch for on and hold etc to brighten or dim ........What i really want to do is get rid of the 2 way circuit . just blanking one off and just using 1 dimmer .. so of the 4 wires in the original switch i need to know which ones i can use for a 1 way dimmer .The other surplus wires will be insulated in dimmer .. The other switch will be blanked and wires again insulated .

I hope that is little clearer .Thanks

[333rocky333]

Bit unclear to your existing set up,

Firstly are you sure new dimmer does NOT need a neutral to work

You need to establish where the live is, proberly the 2 wires on the common,
And where switchlive is proberly on other end switch, common.

If so you use the two reds together from the common already as your live in on new dimmer
and one of the strappers old L2 as the new dimmed output

seal off the other strapper old L1 safely

At the other end the switch your removing should have 3 reds
common L1 and L2.

You need to find the same strapper from L2 at the other end, will be same colour but could be on L2 Or L1 ?

This you join to the wire from the common terminal switchlive.

The other unused strapper coming from other switch L1 might be on L1 orL2 ? again seal off

May be wise to check all works correct by using a cheap on/off switch first rather than risk blowing your new dimmer

Connections for dimmer if one way will be a live in and a dimmed live out , check instructions for what is what.

If only L1 and L2 and NO common on the dimmer it proberly dont relate to the L1 and L2 AND common that is standard on the two way switches

Cover unused switch wiring with blank plate so accesible do not plaster over

[chris _uk]

On wiring diagram for touch dimmer .Neutral into L2 live into L1 ....There are no other wires involved .The switch is 2 gang 1 way ,in other words it can be used to dim 2 lights seperately.

On original switch plate (for easy description...draw a triangle) and at top is common ... 2 red wires , then L2 ...red wire ....L3 ...red wire .

So am i right in assuming that i could use both common as L1 and use wire in L2 as L2 .. then insulate the wire L3 as not to use ?

Thanks

[333rocky333]

Sorry you have lost me now with the dimmer connections , draw out Two triangles as you say, and draw wires connected as i tried to explain.
May help to work out what you have when you see it

Your description of the dimmer, i cannot see how it can work with no other connections , if two gang it would need Two dimmed outputs as well as the supply cable or cables
Are you sure theres not L1 and L2 for Each gang
And could the L1 and L2 be in and out rather than L and N

If it says you need a neutral it is unlikely there is a NEUTRAL AT YOUR SWITCH so you may not be able to fit it.

If your dimmer was one gang and only had L in And L out connections
then yes you would be right to connect how you say,but you still would need to do something at the other two way switch, as the dimmer and light would only work with that switch in one position.
Unless you fit a 2 way dimmer and keep the 2 way wiring

If you remove the L3 wire from the existing switch now you will see what i mean,the two way wont work, this will simulate where the dimmer will be connected.
As said before check with old switch using common and L2 terminal that you have done it right first before blowing up the dimmer

[rflight]

Can you post the make and model of the switch you are trying to fit. Rocky's description is perfect and easy to follow but you seem to be having trouble grasping this. There is no neutral connection and i doubt if you have a neutral at your switch. Re-read Rocky's post carefully and if you still can not understand it then I suggest you get an electrician.

[333rocky333]

Recheck the dimmer drawing carefully, does the live go to L1 as your live in.

And does the L2 go to a symbol ( O with a X ) inside, then carries on with a wire from that to neutral,this is symbol for the lamp.

That part of circuit past the lamp symbol including the neutral is wired already within the building.
If so L2 is your live out. AND NOT NEUTRAL

If that is all you have then your switch is 1 gang 1 way

[chris _uk]

Hi again

The dimmer is 2 gang 1 way so only need to use one side of plate .... yes the live goes into L1 and the L2 goes to light .. The make of dimmer is suntruth . they have web site .

The original switch is just on/off with 2 wires into common .. 1 into L2 and 1 into L3 .. all wires are red , there are no other colours on these wires ( no sleeving)..

The triangle was just a connection schematic .. with common at top and L2/L3 at other corners

[333rocky333]

Have you sorted this

IF NO try this simpler way
OBVIOUSLY TURN POWER OFF WHEN CONNECTING
REINSTATE ONLY FOR TESTING


FIRSTLY
Leave the SWITCH ON FOR NOW the one with 4 wires in ( call switch A ) and remove L3 wire from switch A and seal off.

We assume this is where the dimmer is to go.
We assume you now dont want the two way or other switch no more, your post 1 and post 2 appear to conflict.
We assume there is other connections on the dimmer even though there is because only L1 AND L2 you want to use as 1gang and leave other gang 2 unused.
We assume there is 1 wire in each terminal of the other switch as this is essential if it was two way originally.
We assume L2 is now not neutral as stated in post 3

********************************

you now have same connections as where the dimmer will go LATER.
2 wires old (switch A) common, will go to dimmer L1
1 wire old (switch A) L2, will go to dimmer L2

********************************

Now try the switch the light will only work sometimes depending on other switch position (call switch B)
THIS IS because the old L1 and L2 only link between switches
There is no wire from switch A to the light!
The common from switch B actually goes to the light.

so now

TOTALLY Remove other switch call SWITCH B
MARK THE COMMON WIRE

We assume this has 3 wires as you failed to say

There is a 50/50 chance L1 andL2 at switch B are same as other switch A
JOIN L2 to the common wire
Return to switch A power up and does the light now work with switch A
IF nothing isolate and this time Join other wire L3 to the common
Power up and try light again
Once correct seal off spare wire

If happy now isolate and replace switch A with dimmer using Same as said above earlier, 2 wires onto L1 from common and one wire from L2 goes to L2.
Happy Dimming!