Adding additional switch+light to existing 2 way circuit

[rjm2k]

You need to find the junction box in the ceiling, that's where all the work is done.

It shouldn't be too hard, since someone must have put it there, you will probably find a panel cutout in the floor above, either that or you will need to lift some floorboards.

What you were planning would require lifting anyway just to run new cable to the switch.

 

[markfleet]

You have a permanent live there - use a (proper 2-pole) voltage detector to identify it.

Not sure exactly what you mean. I have used a meter to test between the earth and the 3 wires in the switch (always black cable on meter to earth). Is this an ok way to do it? As mentioned the black wire in the switch will be live but then the red live and black not when I change the other switch. I cant see how any of these are permanent lives. Am I missing something obvious? Also tested using one of them screwdrivers with the light in it (sorry don't know the name)

 

[markfleet]

Bump

 

[markfleet]

Managed to find a junction box when lifting the floorboards as below:

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• markfleet
• 1 Dec 2012
• 1

Closer pic of wires:

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• markfleet
• 1 Dec 2012
• 1

The red appears to we permanent live, not sure about black and looks like there is earth.

The two thinner wires at the bottom of the picture go to the old light fitting but neither are coming from this junction box- one heads in the direction of the switch and the other possibly going to fuse box (fuse box is in adjacent room below)

Is it likely that this junction box is for the lighting? If it is then I can take the earth presumably. Is there any way I could also use the live?

Again many thanks for your assistance.

 

[ban-all-sheds]

I'm struggling to understand what's going on - you have a switch with a permanent live already there, you want to make it a 2 gang, and therefore will need to have a permanent live going to each gang, but you don't want to use the existing one for both gangs, you want to pick a new one up from a junction box and run 2 to the switch?

Also, as I said, you should not just assume that the earths are continuous.

 

[markfleet]

Ban-all-sheds : I am going to test the earths before using. Regarding the positive, I am just worrying that I dont have a permanent live within the existing switch. Would permanent live not always be permanent irrespective of the other switch (within the 2 way circuit?). Currently 1 wire within the switch will be live but change to another wire when the other switch (2 way) is switched. Does that make sense? How should I use this as a permanent live??

 

[markfleet]

Sorry still really stuck at this last point!

I have now put in all the cable going to new light, new junction box I added in the ceiling void including earth which I tested and brought to the orignal light fitting too.


I have swapped out the old dwitch for a 2 gang and the last thing I need to do is wire in the new gang (earth and live) to this switch. Cable is there ready.

I am still stuck on the permanent live side of things and hope I am not being daft!

Going back to the orginal switch (remembering it is 2 way with second switch in hallway. Also remembering I do not want the new additional light to be 2 way) below is how it was wired:

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• markfleet
• 24 Nov 2012
• 1

The black is initially live and 2 reds not live. When the second switch is pressed, the black is no longer live but instead the top right red is live. The other red is never live. What should I be using as permanent live to loop over to the second gang in the switch??

Really really stuck now and worries I don't have a permanent live to use!!!

 

[markfleet]

Ok I am going to make some assumptions. I think the original 2 way lights are wired as followed:

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• markfleet
• 3 Dec 2012
• 1

I am going to assume that the switch in my lounge (from where I am trying to add an additional light on a seperate switch) is S2 in the diagram and S1 is the other switch in my hall meaning I don't technically have a permanent live in for the new light.

Is there a way I can still wire this using what I have already there? Or am I going to have to find another source of power? What are my options?

 

[ban-all-sheds]

Ok I am going to make some assumptions. I think the original 2 way lights are wired as followed:

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• markfleet
• 3 Dec 2012
• 1

You shouldn't wire things up on the basis of assumptions, but it seems highly likely (apart from the cable between the 2 switches being red & black).

I am going to assume that the switch in my lounge (from where I am trying to add an additional light on a seperate switch) is S2 in the diagram and S1 is the other switch in my hall meaning I don't technically have a permanent live in for the new light.

Nothing "technical" about it - you don't have one.

Is there a way I can still wire this using what I have already there?

No.

Or am I going to have to find another source of power? What are my options?

You need to find a permanent live from the lighting circuit.

Options include replacing the twin & earth between the switches with 3C+E to take a permanent live to S2, taking the live from the main loop, or just taking the loop to the new light and running a conventional drop cable to the new switch.

I'm not convinced that any of the JBs you've shown are on the lighting circuit.

Don't forget the rules for any new concealed cabling.

//www.diynot.com/wiki/electrics:walls

Talking of which, where do the cables on the left of this picture go?

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• markfleet
• 1 Dec 2012
• 1

Up the wall to the left of that timber upright?

 

[markfleet]

Cables on the left of the picture go to the fusebox itself so I would think there must be a permanent live there somewhere for the lighting circuit. I am going to see if I can find one. There is a perm live within the junction box under the floorboards however I think this is for the sockets (on a different fuse). At very worst (Want to avoid) I presume I could use this with a fused spur. I have already put the 2c+E in to the switch so don't want to change this but will have one wire free anyway as neutral is coming from the ceiling void seperately from the original light. I will therefore use the free wire to take the perm live down to the switch. Can you see any issues with this?

 

[Spark123]

Was just going to say that those wires in the JB look a bit big for the lighting circuit.

 

[markfleet]

I have 3 cables under floorboards which could potentially be lighting from fusebox - two 1.5mm cables and one 1mm. Is there a way I can know without having to guess / cut in to them?? they all come from fuesbox and head in same direction where I cannot follow.

 

[ban-all-sheds]

Which circuits in the fusebox have those size cables?

 

[markfleet]

Just a quick note to say thank you for the assistance.

Last night I found the perm live I needed from the lighting circuit and have done the necessary wiring. Original 2 way light and additional light on seperate switch all now function as intended, have tested Earths etc.

Cheers