Fitting wall light with dimmer switch

[andygprs]

Hi there,

The room my little boy stays in when he visits is being renovated / plastered for him, and so it's a good opportunity for me to chase out the wall for wires etc. At the moment there is just a central ceiling light and an on/off switch by the door. I would like to create a wall light with a dimmer switch so that I can use it as a night light for him.

I have been in the loft and can see where the cable for the main light comes through the ceiling.

The simplest thing I can see to do is to 'piggy back' off the connection in the ceiling rose, drop the cable through the ceiling and attach to a dimmer switch. However, I'm sure this isn't the correct way to do things and actually the wall light probably wouldn't work when the main light is turned off.

Are there any simple diagrams for a novice to use to wire this up? The wiring with the various junction boxes etc are quite accessible in the loft.

I have to get this done by Monday night as the plastering starts Tuesday!

Thanks,
Andy

 

[plugwash]

The thing about lighting circuits is that there are important basic principles and then there are loads of variants on the actual wiring arrangements.

The two most important things to remember with lighting circuits
1: a switch acts to connect and disconnect a load from the supply. As such it must be connected between the live of the supply and the live of the load to be switched.
2: electricity doesn't care about the color of the insulation. When a core that is not red or brown is being used as a live core it is supposed to be marked with sleeving but in practice it often isn't.

So obviously the first thing that needs to be done is to find a place from which you can get both permanent live and neutral.

Whether this place is the light fitting, the light switch or a junction box depends on the wiring layout. It shouldn't be too hard to figure out though if you look at where the cables go and how they are connected at each position.

One you have worked out what is going on with your existing wiring you can then decide what the easiest way to proceed with adding your new lighting is.

 

[andygprs]

Couldn't get the external link to work but the internal ref seems to work...thanks.....

Hi there,

Being all sensible (not like me) I'm going to chase out the wall and put a cable through the ceiling ready and also try to fit a cable up the channel from the existing light switch through to the ceiling space.

In the meantime I found a couple of junction boxes which I've uploaded. This one seems to be a major one close to the area that I'm working in. The south most pole was live. PS the earth wires are unshielded and can just about be seen outside of the junction box at the bottom of the pic.....

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• andygprs
• 26 Apr 2008
• 1

This image shows another junction box that linked in to the above box via the cable going off to the left. The north most terminal was live.

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• andygprs
• 26 Apr 2008
• 1

In both cases the light in the room in question was off.

Does this give enough info to help me get things wired up?

Thanks for your help!
Andy

 

[breezer]

andygprs, in order for your pictures to show in your post you need to click the

button

and remove the / from the first set of [ ]

 

[andygprs]

Hi,

Thanks for that - edited and waiting

Andy

 

[plugwash]

In the meantime I found a couple of junction boxes which I've uploaded. This one seems to be a major one close to the area that I'm working in. The south most pole was live. PS the earth wires are unshielded and can just about be seen outside of the junction box at the bottom of the pic.....

That needs to be sorted.

In that junction box you have a permanent live terminal (the terminal with loads of red wires), a neutral terminal (the terminal with loads of black wires), and two switched lives for two different lights.

What I would do is mount three four terminal junction boxes on a board and do a conventional junction box layouts for the two existing lights and one for your new light.

note: the above diagram is in new colors, for old color cable use black in palce of blue and red in place of brown.

Remember to mark which cable is which before disconnecting anything.

 

[breezer]

there are no earths on some of the cables, and that cable is silver and multistranded.

it needs a re wire

 

[andygprs]

Hi,

I'm a little bit nervous about doing so much re-wiring as my first task. I've done some more digging (loft insulation is making me itch) and this is what I've learned.

First to clarify, the connection between the first image I showed before (where the earth was unshielded and outside the junction box) and the second JB (where you can see green earths within it) is shown here:

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• andygprs
• 26 Apr 2008
• 1

Then the next photo has an led torch propped between the two grey wires coming out of the first JB. These two wires come out of the top right of the first JB:

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• andygprs
• 26 Apr 2008
• 1

Those wires go through the ceiling as shown in the next pic, and as far as I can tell must go to two light switches, one of my bedroom and one to my son's room - the one I want to work on:

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• andygprs
• 26 Apr 2008
• 1

This last picture is a view of the first JB again. The top left cable is the one that goes to the main light in my son's room.

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• andygprs
• 26 Apr 2008
• 1

I hope this sheds some light on the wiring arrangments?

What is the minimum that I would have to do to acheive what I want to acheive? I'd rather not re-wire everything if I don't have to. Or if possible, I'd like to do it in phases. Get my son's wall light and dimmer switch put in, and then sort everything else after - if it really needs to be sorted out?

Cheers - all this help is really appreciated.
Andy

 

[breezer]

i did notice there are some earths, but i also noticed some have no earth.

I also notice the cables are very old

connecting to a cct with no earth can be dangerous

 

[andygprs]

My other questions still stand......sorry to be stupid, but what does CCT stand for?

 

[andygprs]

Trying not to rush ahead, but here's my guess, if we look at the first JB, if the top left cable is my son's room light then either the middle or lower left must be the primary mains supply?

I can't decide if the lower cable is the supply cos its live and neutral go where all the other lives and neutrals go, or if it is the middle cable cos although it appears to have the neutral go off to a different terminal, it is the only one that appears to have an earth cable.

In either case, the second JB just appears to have straight forward live, earth and neutral - no weird switching stuff. Is that correct? If so, could I not just patch in there and wire up the new wall light as per Plug Wash's diagram?

I could well be confused about all of this!

Cheers,
Andy

 

[breezer]

My other questions still stand......sorry to be stupid, but what does CCT stand for?

cct = circuit

 

[andygprs]

Thanks. Well, I've chased the walls out - one for the switch cable - it wouldn't fit up the existing channel and the other for the wall light.
I've fed the cables through the channels to the loft.
I've wired up a double dimmer switch - two independent dimmers on the same panel - one to the existing main light (works fine) and the other is for the new wall light.
I haven't attached the new cables for the new wall light or wall light dimmer switch to the mains yet.
I have bought a 4 post junction box ready.....so I'm hoping to get some yes / no answers to my planned wiring before I actually connect it up!

At least everything I need to do in the room is done now so the plastering can get done while I decide what to connect up where in the loft!

Cheers,
Andy