Ceiling light fitting help

[mg2]

Hi,
I've looked at the reference diagrams and read back through other topics but I'm still stuck.
I am replacing a kitchen ceiling light. I have removed the old rose and foolishly didn't note the wiring exactly.
I have three grey cables. Two of them have a red,black and earth (the earths of these two cables have been joined together by a sleeve). The other cable only has the red and the earth exposed.
Now I'm guessing the "red & earth" is my switch, but I would expect it to have the black with red sleeve live return wire from the wall switch but it's not there! The black wire is cut flush with the end of the grey casing.
And I presume the two cables that have their earth joined represent the mains "too/from" previous lights.

Also, the new light doesn't have three blocks like the old one, so I presume I need a terminator block to hold the mains loop Lives?

Any ideas how it should be wired to the new light?

 

[Inspector]

Am I to understand this correctly. You have ...

One T&E incoming to the ceiling rose
One T&E outgoing from the ceiling rose
One single red & E

Check there isn't another cable (probably single red)


Questions - Do any of the black cables have a red marker tape on them?
Do you have a multimeter?

 

[securespark]

Need a MM to check out the cables, but my guess would be you have a live feed in and live feed out, and the single red is a switch wire, the feed for the switch may have been sourced from elsewhere, possibly a back-to-back switch.

If you put a meter (set to ac volts) on the neutrals (put together in a block) and on the single red, does it show 240 when the switch is on?

 

[mg2]

One T&E incoming to the ceiling rose
One T&E outgoing from the ceiling rose
One single red & E

Yes. No other cable that I can see. None have red tape that I can see.

One thing I should mention is that there are two switches that control this light but I assumed the second switch came off the first and wasn't relevant to the rose wiring.

So the single red and E are probably the switch and the the feed is from somewhere else? I don't understand that part, is it possible for a switch to work with just the live to switch but no wire coming back to complete the circuit?

I will check it with a MM.
Thanks for your quick responses.

 

[breezer]

the earth must be just an earth it should NEVER be used as a condutcor

 

[mg2]

Yeah, sorry, I didn't mean the Earth was live to the switch, just that it physically goes there. When I removed the old light it definitely was connected to the Earth terminal.

 

[kendor]

It's bad practice to run single cables like that you need a return cable in the same sheath otherwise you may create Eddy Currents which is bad news.

 

[Inspector]

eh ???

 

[kendor]

sorry i realise that this is a DIY forum and my statement will confuse non sparky people but let's just say don't do it! (run single cables).

 

[Inspector]

I agree, but in the case of the lighting circuit mentioned its most likely necessary to run a single red & earth cable from the ceiling rose out to the switch(s) and a single red returning to the ceiling rose.

 

[kendor]

Yes that's supposed to be the case but he has the return cut off short in the sheath and therefore it is a single cable. although in this case Eddy's shouldn't be a problem as there is no current flow down the red (unless horror of horrors he's using the earth as a return in which case the return would cancel out any eddy effects) but i was generalising in my comment about running single cables around.
I've seen in the past botched attempts at wiring two way switching circuits using T&E where the bodger has obviously tried to copy from a diagram thats shown the single core trunking method as opposed to the T&E conversion method and only used one core of the twin down to the switches and a twin for the strappers between!

 

[mg2]

I connected the single red to the SWL and the E to Earth and it works, but since there is no return to the rose is that a bodge method or not for a two-way? (apart from Eddy's)

 

[securespark]

MG

As i said before, the most likely explanation is that the switch is fed with a live feed from elswhere on the circuit. Often when switches are back to back (for example) they share one live feed, so one light only has a single returning to the rose position as a switch wire.

 

[kendor]

Lets get this straight you must never have single cores being used on their own in a T&E cable(in this case S&E) each twin, 3 core whatever,must incorporate the circuit live aswell as it's return to cancel out the eddy effect otherwise cables may get extremely hot resulting in cases of electrical fire.

 

[plugwash]

then why the hell is single red and earth made?

where did you find this info?