Wiring a dimmer with uncertain wiring.

[chrisser1976]

Our living room had three wall lights which I’ll name A,B and C. I wanted to replace these wall lights with Halogen 240v 50w spotlights controlled by a two gang remote controlled Home Easy HE108. For any one that doesn’t know this dimmer it’s rated at 250W (which from what I can find on the net seems to be in respect of halogen and indeed that load does not send the dimmer into auto shut down unlike higher loads I’ve tested) per gang and has a blue standby light for each gang which comes on when the switch is connected but goes out when you switch the lights on.

For simplicity I’ve extended the cables to the old wall lights with twin and earth and routed them along the top of a dedo rail then up into the roof space and to the spots. I’ve got one light fed from A, four from C and five from B.

A and C seemed to be operated by one switch so I’ve put 250W on those between the two feeds so they can be operated by a 250W dimmer.

B also has 250W on it.


Now I’ve come to re-wire the switch I’m presented with two red and one black wire offered up to the switch. One of the red cables is ‘loose’ and the other is in a twin and earth cable along with a black cable and an earth.

What I’m trying to achieve is this: Half the spots are controlled by one of the dimmers gangs and the rest by the other (I’ve arranged the spots so that half are reflected in the TV and half are not so I can have light at one end of the room without the TV end being lit or lights reflecting in the TV.

Now the questions...


Is the cable to the dimmer switch correct - i.e should there be another black ?

How should switches be wired up ? Each gang has three terminals - Live, Load and S.

N.B I spent a few hours last night checking the continuity to the lights from the cables at the switches and all is well.

Can post images if that helps.

 

[Taylortwocities]

Some answers, and some questions. Questions first

The cables to the( existing) switch. Where do they go to?
The cables to the existing switch. What colours are/were connected to which terminals?
That spare red, was it connected to anything, at all?
Do you have a multimeter or a voltage tester (NOT a neon screwdriver)

Coments

For simplicity I’ve extended the cables to the old wall lights with twin and earth and routed them along the top of a dedo rail then up into the roof space and to the spots.

That is not allowed!
What is to happen to the old wall lights?
You cannot cover them over and leave them in the wall
You cannot run cables behind the dado rail.
If the old wall lights are redundant then you must remove all of the live cables out of the wall.
The cables from the switch to the new lights should go vertically from the switch up the wall and into the ceiling void.
See here http://www.diynot.com/wiki/electrics:installation_techniques:walls


At your switch you will need a connection to each light cluster that runs to the switch. Each light cluster will be terminated onto the neutral of the lighting circuit supply.
Also at the switch you will need a live feed that originates from the same lighting supply. The wiring diagram that comes with the HE108 shows you.

In your existing lighting wiring do not assume that a black wire is a neutral. It will probably be a switched live.
That is where you need the multimeter.

 

[chrisser1976]

Yes I have a multi meter. Not sure what to do with it though !

The old wall lights have been removed. I then used block connectors to run cable from where the old lights where up through channels I've chased out in the wall and up into the ceiling. Nothing is left in the wall except for cable and block connectors. All the cables run to ceiling lights - nothing has been terminated and just shoved back into wall cavity.

The cables run along the top of the dedo which I can box in if needs be. If that's not allowed presumably I can just chase a channel following their route and conceal them into the wall.

It's sounds as if there should be two live (RED ?) cables to the switch and two (BLACK ?) at the mo there is only one black cable which had been looped between gangs on the old switch.

 

[ban-all-sheds]

The old wall lights have been removed. I then used block connectors to run cable from where the old lights where up through channels I've chased out in the wall and up into the ceiling.

Not allowed, as you would now know if you had read the Wiki article.

Nothing is left in the wall except for cable and block connectors.

That's exactly the problem - that's not safe.

nothing has been terminated and just shoved back into wall cavity.

You yourself said that you terminated the cables to/from the lights in a piece of choc-block and stuck it back in the wall!

The cables run along the top of the dedo which I can box in if needs be. If that's not allowed presumably I can just chase a channel following their route and conceal them into the wall.

On top, i.e. not buried in the wall, is fine - chasing them in would not be.

 

[chrisser1976]

Just to clarify the blocks were used to EXTEND the cables not to terminate them. The original cables just run to new lights as I've added extra cable to reach the new spots. So are you saying I can run cables on the surface of walls but not actually inside of walls ? I don't think you do mean that but maybe I mis-understand. Why can't I run them along dedos ?

Thanks, Chris.

 

[ban-all-sheds]

Simple question - have you or have you not read the Wiki article on concealing cables in walls?

 

[chrisser1976]

Yes I've read them. Probably need to re-read a few times though to be honest.

 

[Steve]

You have live cables in a wall. Nobody, besides you, knows they are there. There is no indication on the wall that indicates the presence of electrical cables. Why do you think this would ever be considered safe? We cant just go around throwing cables behind plaster willy nilly.

The only way to make this safe (and compliant) is to fit a blanking plate and backbox at the location of the old lights. This then shows there is possibly a cable leading from that point and creates "safe zones" horizontally and vertically from this point, where one should not drill.

 

[skenk]

You can put them behind the dado, assuming you mean on the surface of the wall, hidden above the dado/picture rail. You CANNOT have cables hidden in walls at a depth of less than 50mm unless they are in safe zones (see wiki) and you CANNOT extend cables with a chock block unless it is inside an enclosure and accessible for maintenance/inspection.

 

[chrisser1976]

Thanks Skenk and Steve - yeah all makes sense that chaps so I'll re-think the cabling. I did think the choc blocks need to be in an enclosure and have bought some. It'll be tricky to bury 50mm in to brick but I'll think of something.

 

[flameport]

I did think the choc blocks need to be in an enclosure and have bought some.

They also need to remain accessible - you can't put them in a box and bury it in the wall.

 

[Steve]

It'll be tricky to bury 50mm in to brick but I'll think of something.

Dont, your house will fall down.