Trying to add another light but 4-core cable confusing me.

[craigdorney]

Hello,

Currently I have two outdoor lights that are switched by a light switch in the hall.

I want to add a PIR and an additional light to this setup so that 3 lights are triggered by the PIR. I thought this would be straight forward - but the way the wiring is done is confusing me a little - hence I'd like to seek your advice.

In my Hall I have a dual light switch. The first switch (left hand side) switches the hall light. The second switch (right hand side) switches the two outdoor lights. Each outdoor light is at the corner of one side of the house. There is a single flat grey cable from each light that enters the roof space and then disappears under the upstairs floor boards. This is an old scottish cottage property where the upstairs rooms are in part of the roof space.

At the switch the outside lights are wired using 4-core and earth cable. Two of the cores (one brown and the other black with a brown sleeve) are used as live - it seems to me - and are attached to L1. The live feed is from the "com" of the adjacent Hall light switch. The other two cores are connected to Neutral (via a screwblock within the switch socket housing (one core is blue and the other is grey with a blue sleeve).

I have very limited access to the roof space and I can't ascertain where the 4-core earth cable goes to - as again it seems to disappear up the wall and under the upstairs floorboards.

The house was re-wired by a trained/competent electrican, prior to us moving into the property - so I'm assuming/hoping there's a known/standard way to do this - that I don't know about as I'm just a DIY'er.!!

Can some one explain how this circuit might be connected up... I don't understand how the 4-core cable gets connected to the two lights as they only have a single cable from each of them.

If I had X-ray equipment I might be able to see if there are any junction boxes under the floor!!

Thanks in advance for any help,

Graham

 

[rebuke]

Hmm, this seems odd - I've not heard of 4 core and earth before, any chance of a picture of the back of the switch etc?

 

[craigdorney]

Hi,

not sure if this is going to work - but here is the link to the picture.


//www.diynot.com/network/craigdorney/albums/3468/13606

Thanks

 

[rebuke]

Difficult to tell without seeing which core comes from which cable etc, but at a guess (I must stress this is a guess, don't rely on it etc etc) what you've got is a loop-in at switch arrangement (its more common to loop at the rose, but nothing wrong with doing it at the switch), and they've taken feeds to two fittings through one cable. Presumably the reason for this is so the fittings could later be split up, if you wanted to switch them independently for any reason.

In terms of adding your PIR and additional light, you're going to have to find where this 4core and earth cable you describe splits in to the two T+E cables going to the actual lights. Hopefully this will be somewhere accessible, as unless it's been done using e.g. maintenance free junction boxes (even those are arguable), or crimps, the connection should be accessible to comply with the regs. If not, and it's buried under floorboards, then you're unfortunately going to have to lift boards until you find it...

 

[craigdorney]

Hi,

thanks for your comments - this is what I feared - that there is a connection/juntion box "somewhere". Don't know why he went to the trouble of using such method in the first instance.

by the way ..I added a new picture here: so you can see the cables better.

//www.diynot.com/network/craigdorney/albums/3468/13610

Thanks

Should add the bit of black tape on the brown wire going into L1 atthe top is me putting some insulation on the wire as it look like it had been caught on something.

The 4-core cable is the middle cable - this feeds the outdoor lights.

 

[ban-all-sheds]

Don't know why he went to the trouble of using such method in the first instance.

It's increasingly done, as it avoids the problems associated with replacing a traditional loop in rose with a light that only has L/N/E terminals.

See //www.diynot.com/wiki/electrics:lighting

The 4-core cable is the middle cable - this feeds the outdoor lights.

It's 3-core & earth, not "4-core".

Can't think why it was used, as there's going to have to be a junction box somewhere to split off into two cables, as they go to separate places.