wiring downlights

[bob]

Hi all,

I am in the process of replacing a pendant light with some downlights. I believe I have a lighting circuit similar to 'Method 1' on this page

is based on the folllowing observations: (a) I have a single 3 core cable entering the rose, so I don't think it is 'Method 2 - loop in wiring' a

(b) I can see no visible junction boxes in the ceiling void so I don't think it 'Method 3 - junction box wiring'.

I have 3 diy books (Collins, B&Q, DK) and none of them seem to describe this circuit. Does anyone know what it is called?

Basically what I need to know is if I replace the rose with a 20A junction box, do I connect similar colour cores from the downlights to the circuit cable from the switch in a star topology i.e.

1 red/2 browns at 1 terminal (1 red back to the switch, 1 brown to each downlight) 1 black/2 blues at 1 terminal (1 black back to the switch, 1 blue to each downlight) 3 earths at 1 terminal (1 earth back to the switch, 1 earth to each downlight)

I am replacing two pendants with four downlights, hence why I am only connecting two downlights to each junction box above.

Any advice, greatly appreciated.

[Christian McArdle]

Don't. It is environmentally irresponsible.

By "3 core" cable, do you mean two proper cores and an earth, or three proper cores and an earth?

You will need a lot more than 2 downlights to replace a pendant fitting, which is why downlighters are so irresponsible.

Christian.

[John White]

The junction box could be quite a distance from the fitting, so it's probably this method.

Don't worry about the method name. Different books use different names anyway. :-)

Yes that's correct.

To be pedantic the existing red wire is your "switched live", the black is the "supply neutral" and the earth is the "supply cpc" - according to one book anyway. :-)

John

[bob]

Sorry, yes 2 core and 1 earth.

John just to confirm, I take it doesn't matter if the red/black/earth earth wires are running back to a switch (Method 1) or a junction box (Method 3) as this is the supply regardless, correct?

I've had a look in the double switch, there are 3 cables entering it,

2 of which run to a pendant and the other I presume is the circuit cable?

[Christian McArdle]

Yes, it is of no relevance. You have the switched live and neutral for the existing light. This is all you need for the replacement, too.

Christian.

[John White]

That's right. As the new lights are using the same switches, all you are effectively doing is replacing one light fitting with another.

It depends how it is wired.

If you have:

- all the neutral (black) wires are joined together - all the earth wires are joined together - the three live (red) wires going to switch terminals - a wire linking the two the switches

then the cable that is joined to the link wire is the supply, and the other two cables go directly to the light fittings.

John

[bob]

Yes, that's exactly how it looks :-).

Also, there are some main circuit cables (looks like 3 core and earth) running above the downlights through the joists. They are not touching the lamp but are close enough to concern me, what termperature is this PVC outer sheeth of this cable typically rated to?

I notive the wires which go to the lampholder have a fabric like sheeth, is this rated to higher temperature than PVC outer sheeth of

2/3 core and earth cable.

And finally, is it ok to use green/yellow electrical tape to cover the "supply cpc" or must I use sleeving complying with BS 2848 to meet Reg.

543-03-02, as indicated by this post again for you help on this.

[John White]

The current carrying capacity of PVC cable is usually specified at 70 Degrees C.

Push the other wires as far away from the downlighters as possible. You can usually find enough slack to do this.

Make sure that the downlighters are far enough away from the joists too. This is typically 75 mm but check the installation instructions.

You should really have checked for other wires before you cut the holes, and repositioned the downlighter accordingly. But of course you realise this now. :-(

Yes - much higher.

John

[bob]

Thanks John.

[Owain]

Probably glass-fibre, and yes it's much higher temperature.

You must also affix to your consumer unit the appropriate warning label that the installation uses two different wiring colour schemes.

Owain

[meow2222]

the ceiling rose _is_ a junction box. Hence replacing it is a job that doesnt need doing. Nor do you need to understand the wiring, just connect to the same connections the present light is connected to.

As for downlighters, if you mean halogens I'd recommend doing the cost calculations first. With eg 6 downlighters you'll be replacing bulbs 6x as often, and downlighting costs thousands in extra run cost over its life. It also heats up the place in summer... it really is a classic example of style over function. And environmentally it wont mark you out as smart or caring. And they have other problems, but I wont bore us all.

NT

[marvelus]

Cutting holes in the ceiling reduces its fire protection for one.

[David Hansen]

On 19 Sep 2006 12:05:54 -0700 someone who may be [e-mail] wrote this:-

A junction box to which no more than one lamp should be connected, unless it is specially designed to take more than one lamp (I have never seen one but I suppose they exist).

Of course there is no restriction on connecting the lamps via cables from the back of the rose, assuming there is enough room so that this can be done with good workmanship. However, that leaves the rose on the ceiling, which would probably be frowned upon by someone who presumably wants downlighters for some visual reason.