Changing a ceiling light, but confusion over wires


Postby milliefive » Mon Dec 31, 2007 1:20 pm

Oh dear. Last night we tried to change a ceiling pendant light fitting. We removed the old fitting (which was the bog standard white plastic rose type) and tried to fit the new one. But, we can't. The new light has a plastic connection box instead of the wiring terminals inside the rose. There are two wall switches controlling this light.

What we have are:

Inside the loft - 2 white cables each containing 1xblack, 1xred, 1xbare (neutral) wires.

Inside the light - 1xblue, 1xbrown, 1xyellow/green wires

One connection box with 4 terminals.



I know to connect the red to the brown and the blue to the black and so on, but which of the ceiling cables do I do it to,

What do I do with the other one?

One must be the switch cable, but if I have 2 switches, why only one cable?

I cannot find any information showing exactly the set up I have and this should have been such an easy job, but now I am going to have to get an electrician out with all the cost and wait that implies. Arrrgh!

Can anyone help?

Thanks!
milliefive
Posts: 5
Joined: Mon Dec 31, 2007 1:10 pm

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Postby BLAKEY1963 » Mon Dec 31, 2007 1:57 pm

[quote="milliefive"]Oh dear. Last night we tried to change a ceiling pendant light fitting. We removed the old fitting (which was the bog standard white plastic rose type) and tried to fit the new one. But, we can't. The new light has a plastic connection box instead of the wiring terminals inside the rose. There are two wall switches controlling this light.

What we have are:

Inside the loft - 2 white cables each containing 1xblack, 1xred, 1xbare (neutral) wires.

Inside the light - 1xblue, 1xbrown, 1xyellow/green wires

One connection box with 4 terminals.



I know to connect the red to the brown and the blue to the black and so on, but which of the ceiling cables do I do it to,

What do I do with the other one?

One must be the switch cable, but if I have 2 switches, why only one cable?

I cannot find any information showing exactly the set up I have and this should have been such an easy job, but now I am going to have to get an electrician out with all the cost and wait that implies. Arrrgh!

Can anyone help?

Thanks![/quote]

milliefive

you could start by going to doc s projects section on lighting
the diagrams r quite helpful and might guide u in the
right direction.
BLAKEY1963
BLAKEY1963
Posts: 654
Joined: Wed Jun 13, 2007 10:57 pm


Postby kbrownie » Mon Dec 31, 2007 2:35 pm

Hi milliefive,
If understand you right, what you have is an in-coming Live (Red), Neutral(Black) and Earth(Green+Yellow).
The other Cable containing these coloured cables are to your Switch known as switch wires.
I don't know how your connection block is set up, so i'm hoping i've got this right.
1) Your reds should be connected together (that will put live supply to switch) and with nothing else!

2) The Neutrals(black) should be connected either side of the lamp. one to the Live(Brown) this should be your switch wire coming from the switch and should have Brown tag or sleeve on it. (i'm guessing it don't)

3) The other Neutral(black) to the Neutral (Blue) on lamp, this is the in-coming supply Neutral.

4) All earths connected together

So if connection block has has 4 Terminals they should follow as above!
Hope this was usefull if any problems reply. Be safe at all times and isolate before you do any work.
Best of Luck
KB
kbrownie
Posts: 1756
Joined: Mon Mar 05, 2007 9:36 pm


Postby milliefive » Mon Dec 31, 2007 5:01 pm

kbrownie, thanks I can follow this. Just to make 100% sure: 3 of the 4 terminals in the connection block have 2 wires in, the 4th one has 3 (all the earth wires).

The only brown wire is in the light, the two cables in the loft both contain just red black and bare. How do I tell which is the switch cable?

Can you also explain why I have only one switch cable when there are 2 switches?


Thanks!
milliefive
Posts: 5
Joined: Mon Dec 31, 2007 1:10 pm


Postby kbrownie » Mon Dec 31, 2007 5:20 pm

Ok milliefive,
Can you get in to loft and see were cables come from, the cables coming from another light fitting will be your in-coming supply. If you can see cables coming up from wall where the switch is near they are your switch wire (logical I know). You really need a tester to be sure. The light will opperate anyway.
All Earths Grouped together
Black to Lamp Blue
Black to Lamp Brown
Reds together.
The reason you only have one switch cable is because the rest of the cables that opperate the second switch are connected between the two switches and not to the light.
Hope that makes senses
Good Luck and a Happy New Year.
KB
kbrownie
Posts: 1756
Joined: Mon Mar 05, 2007 9:36 pm


Postby kbrownie » Mon Dec 31, 2007 5:34 pm

Hi again the bare wires are your earths they should be protected by yellow+Green PVC Sleeve. You can buy these at DIY and Electrical wholesalers not expense and you can cut it in store to required length normal! it is hollow with no cable inside as it slides over bare wire.
Good Luck again
KB
kbrownie
Posts: 1756
Joined: Mon Mar 05, 2007 9:36 pm


Postby ericmark » Mon Dec 31, 2007 6:07 pm

Two way lights do not work as first expected as it would require a junction block in the switch. The school way of showing two way lights is live to one switch common both switch N/O and N/C connected together and from second switch to lamp. But really it works as all connections on switches like to like i.e. Com to Com, N/O to N/O and N/C to N/C and the switch wires from the lamp go to one switches N/O and N/C. This configuration means no junction blocks are required in light switches. Wish I could place pictures to explain. Look at http://freespace.virgin.net/g.palmer/pi ... wo-way.bmp it show both school and real configuration. I know it works done in multisim and fully tested.

All best Eric
ericmark


Postby milliefive » Tue Jan 01, 2008 4:25 pm

THANK YOU! Thank you thank you thank you. The light is up, working, and no one got blown up. What a fabulous New Year!

I have only just discovered this site, what a brilliant place this is!

Millie
milliefive
Posts: 5
Joined: Mon Dec 31, 2007 1:10 pm


Postby ericmark » Wed Jan 02, 2008 12:28 am

Glad to hear it all worked out OK. I have now made a circuit diagram for two way with intermediate at http://freespace.virgin.net/g.palmer/pi ... -inter.bmp
ericmark


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