Adding an extra light to existing circuit

[MidsTW]

I have made a small walk in wardrobe in our spare room and I am adding a light.

I prepared the switch position, switch cable and supply cable. I prepped the cables and then wired up the switch and light rose. I then went to join my supply cable in to the existing circuit.... This failed. I believe I selected a switched live cable as it came from one of two switch boxes for the attic.

This caused the new light to flash when I turn the switch off for the attic light.

Does it sound like this is right and that I just need to establish an actual supply cable to break into?

Cheers

 

[riveralt]

With the circuit dead you need to find a ceiling rose or junction box that you can tap into the L/N/E - run that to your new ceiling rose first.
Then run your live/switch live and earth through/to the switch.
There are alternative methods.

 

[MidsTW]

Cheers riveralt. I also found some old twin cable with no red sheathing. Luckily there is a ceiling rose within reach so I can presumably spur off that?

 

[ban-all-sheds]

Cheers riveralt. I also found some old twin cable with no red sheathing.

What does that mean?

Luckily there is a ceiling rose within reach so I can presumably spur off that?

Does it have the lighting loop there, i.e. permanent L/N/E?

 

[MidsTW]

Ban-all-sheds - I thought it was a supply cable as it didn't come from the switch but when I cut it to add my new supply in I found 2 wires. One with black sheath and one with none. I assumed this was twin core but I only get a light on my electric screwdriver from the black wire when I turn the loft light on.. any idea?

Yes the other ceiling rose I can see has twin and earth and the switched live from what I can see.

 

[Iggifer]

Sounds like you have a single core and earth, used for a switch live to your loft light. Electric screwdrivers/voltsticks are useless for the purpose you want. Get a two pole tester/mulitmeter for the £5 it'll cost you

 

[MidsTW]

Wasn't aware of single core and earth. Just check another ceiling rose and it has two cables going in. Both have 2 wires. One is red and earth (switches live) and the other is black and earth (supply)? What do you think?

 

[Iggifer]

Or, more likely, one is your neutral and one is your switched live

 

[MidsTW]

Sorry I'm not sure I understand now. I always thought you had a twin and earth supply to the rose and then another twin and earth where both are L and N are live (switched)

It's thrown me out seeing cables with 2 wires ...

 

[Iggifer]

Not always. Single core and earth was used a by some a few years ago(you can still buy it). It's impossible to say how your circuit is wired without more investigation. If you only have two single+earth at your rose, it's either looped at the switch, or you have a junction box somewhere.

Check behind the nearest switch first before you go hunting for junction boxes

 

[MidsTW]

Just done some research into single core and earth and looks as if your spot on. Looking at some diagrams where they run a neutral from rose to rose and then a switched live also on a single core. If this is the case. What's the best way to add to this circuit?

 

[AndyPRK]

Not always. Single core and earth was used a by some a few years ago(you can still buy it). It's impossible to say how your circuit is wired without more investigation. If you only have two single+earth at your rose, it's either looped at the switch, or you have a junction box somewhere.

Check behind the nearest switch first before you go hunting for junction boxes

Well neither!

I associate single and earth with 2 way switching.

Neutral runs between roses.
Lives go via the switches. Can originate from rose or cu.

 

[Iggifer]

That's true, but I've also seen it used that way with both standard loop at the rose and switch layouts too

 

[MidsTW]

Thanks guys. The loft light and hall light (two closest lights) both have 2 switches which maybe explain why single core is present?

If this is all correct what is the best way for me to add my new LNE supply cable into the existing circuit?

 

[riveralt]

Thanks guys. The loft light and hall light (two closest lights) both have 2 switches which maybe explain why single core is present?
If this is all correct what is the best way for me to add my new LNE supply cable into the existing circuit?

This would be much better if you could supply us with photographs of the inside of the ceiling rose showing the wiring terminals and the inside of one of the switches.
If, as suggested, you have do have singles and the layout is running neutrals to each ceiling rose with only returning switch lives to the same ceiling roses- then you will need to do the following.
With the Power off.
Identify the neutral (and one hopes the earth) from one of the ceiling roses and run new cable to the new ceiling rose - T&E is fine just use the blue and earth wires.
Then you will need to find the permanent live, going to the switch and interrupt it in the loft somewhere. This means you will have to cut into the circuit and join the cut (permanent live) wires in an accessible junction box. Once this is done you connect a new T&E (just using the brown wire) to this junction box to the permanent live wires and run the cable to the live terminal at the new ceiling rose. From their run your normal live/switch live down to the new switch.
The alternative: Wire neutral as suggested above. Run a T&E (using just the brown wire) from the permanent live at one of the switches to the new ceiling rose and carry on as above.
There are other options.