New Lighting Circuit

[cwhaley]

In my new extension a qualified electrician will be extending the ring main of my existing downstairs circuit into my new extension. He lives nearby and to save him the work, I'll be clipping the T&E cable on the wall in runs to the various sockets (in the safe zones of course) as well as light fittings and the switches.

I've no problem creating the loop for the eight sockets I would like, but I don't know what to do about the wiring for the lighting. The extension consists of a single room, partitioned into a downstairs WC and utility room (so three individual rooms to light), and it sits on the site of the old outside toilet -- the lighting to this was supplied from a spur taken from the downstairs lighting circuit. It entered the WC as a single wire, went to the light fitting, then finally to a switch.

The electrician is now away for a few weeks, so I just wanted to know what I'd need to do to lay the wiring. There will be one ceiling light per room. He said that all switching is done at the switches now rather than the various loops you'd cram into a ceiling rose.

As a disclaimer, although I'm competent at properly terminating wiring into a faceplate (used to make wiring harnesses for cars), I'm not doing that here so that the electrician can do it himself and be confident in signing it off at the end.

 

[terryplumb]

At each switch position there would be 3 twin and earth cables ,a feed in ,and feed out to the next switch position,and the third cable from switch to light fitting. You should mark each one as such. The last switch would only have 2 cables, feed in and cable to light fitting.
Where do you intend to join into the circuit ,at a ceiling rose ?

 

[winston1]

You will not save him much work by clipping wires to the walls. Nor will you save much money which is what I guess you really mean.

Are you really going to have wires clipped to the walls rather than buried? There is no concept of safe zones for visible wires clipped to the walls.

Where you will really save him/her time and you money is if you channeled the walls and fitted oval tube where you want the wires, and also plastered in back boxes.

Regarding lighting you need a cable looped to each switch position and another cable from each switch to it’s corresponding light.

 

[cwhaley]

At each switch position there would be 3 twin and earth cables ,a feed in ,and feed out to the next switch position,and the third cable from switch to light fitting. You should mark each one as such. The last switch would only have 2 cables, feed in and cable to light fitting.
Where do you intend to join into the circuit ,at a ceiling rose ?

That's very helpful, thank you. I've sat and drawn a plan based on what you've written there and it makes sense now I've visualised it. My only experience with domestic lighting circuits has been changing faceplates and ceiling roses.

As for joining into the existing circuit, we were planning to use the existing wire which once fed the outside toilet light. As it is already in place I was told this would be satisfactory.

 

[cwhaley]

You will not save him much work by clipping wires to the walls. Nor will you save much money which is what I guess you really mean.

Are you really going to have wires clipped to the walls rather than buried? There is no concept of safe zones for visible wires clipped to the walls.

Where you will really save him/her time and you money is if you channeled the walls and fitted oval tube where you want the wires, and also plastered in back boxes.

Regarding lighting you need a cable looped to each switch position and another cable from each switch to it’s corresponding light.

Honestly, the saving genuinely is time. He's a neighbour and a friend and the only charge is a few ales! The time saving element comes from me having the time to sit and think where I want to position each socket, switch and fitting, not forgetting chasing the walls on the inside of the existing property to extend the original circuit and drilling through solid brick. I didn't include this bit in my original post because I knew I'd be saving him time.

The wire will be clipped to the wall yes, as it is going sit underneath plasterboard which will be fixed to battens. The idea behind having battens is that I can run services behind rather than channeling through any plaster. I also don't like dotting and dabbing!

Would it be better to run the wire through a conduit?

 

[terryplumb]

Is the circuit protected by an RCD ?
There is no need to run cables in tubing or conduit in the void behind plasterboard.

 

[cwhaley]

Is the circuit protected by an RCD ?
There is no need to run cables in tubing or conduit in the void behind plasterboard.

Yes there was a full rewire in 2008 before my ownership with all circuits protected by RCD. I had it retested this year (a little later than the 10 year recommendation, mind). Made sense if I was having new space added where an electrical cert. would be required.

Thanks. I do actually have lots of (plastic) conduit left over from a completely unrelated job, so I wouldn't have minded. I'll keep it clipped to the wall neatly within the safe zones. At least he won't have to spend his evening or weekend sat with me telling him where I want each socket and switch (which I know fall under regulations themselves with regards to positioning).

 

[winston1]

where I want each socket and switch (which I know fall under regulations themselves with regards to positioning).

Only for new builds. You can put them where you want.

 

[cwhaley]

Only for new builds. You can put them where you want.

Oh okay, I thought I'd read it as "new space". At least that means I can match the height of the existing sockets which are more than adequate for us.

 

[cwhaley]

Sorry to resurrect my old post, but just coming to connect the switches up for the lighting circuit.

My two gang light switch has three entry cables -- 1) supply in (from previous switch) 2) supply to ceiling light 3) supply to wall lights (there is no cable to the next switch as this is the final switch in the room).

Would I be correct in saying that for the two gang light switch, the live/line on the supply in needs to go into the COM terminals (bridged with a brown wire), one switched light goes to L1 and the other switched light to the other L1, with all the neutrals connected in a block?

Before this final switch, all the other lights are one gang switches, so I'm presuming the terminations are the same, with the COM terminals accommodating both the supply in, supply to the next switch and the single wire bridge.

 

[terryplumb]

You are correct, the supply line goes to COM,and bridged to 2nd gangs COM.
All neutrals connect together in an insulated terminal block or wago.
Switched lines to L1.( Each gang)
Earth conductors to earthing terminal on switchplate / mounting box ,as applicable.

 

[cwhaley]

You are correct, the supply line goes to COM,and bridged to 2nd gangs COM.
All neutrals connect together in an insulated terminal block or wago.
Switched lines to L1.( Each gang)
Earth conductors to earthing terminal on switchplate / mounting box ,as applicable.

Thanks for the quick reply. I'd looked at a few diagrams on a lighting website but just wanted to check with somebody. The electrician signing the work off (who will be doing the physical extension to the ring main and lighting circuit) will check them anyway but it's a few weeks away and I'd rather them be correct for him.

The faceplates are those brushed metal type ones and I think they are earthed through the screw holes, but I'll run an earth to the metal backbox as well just as a matter of course.

 

[winston1]

The faceplates are those brushed metal type ones and I think they are earthed through the screw holes, but I'll run an earth to the metal backbox as well just as a matter of course.

The earth need to connect to the faceplate.

 

[cwhaley]

The earth need to connect to the faceplate.

Thanks, yes I think I remember seeing a strip of metal connecting each screw hole to the earth terminal and the metal faceplate which I presume is a way of earthing, but as you say I will run a new sleeved earth wire to the earthing terminal on the backbox.

 

[winston1]

Thanks, yes I think I remember seeing a strip of metal connecting each screw hole to the earth terminal and the metal faceplate which I presume is a way of earthing, but as you say I will run a new sleeved earth wire to the earthing terminal on the backbox.

No, you must earth the faceplate directly so that it remains earthed when the fixing screws are removed or loose.