Is tracing wire in loft too simple a way to find sw. live?

[Meehog]

I want to replace my celiling light in the bathroom, and I'm able to trace the cable in the loft from my ceiling rose to the light switch (pull switch so it's wired at the ceiling), am I right in thinking that the black wire in this cable will be the switched live? There is a black, a red and a green wire in the cable, and there are no red sleeves on the black wire to clearly identify it, but that is very common from what I've read.

Going from the wiring diagrams on this site, It appears to me that this is indeed the switched live, but I've seen so much discussion on how to find it, by using a multimeter etc, this just seemed too easy and I've put doubt in my mind!

Thanks,
Phil

 

[Adam_151]

Yes, if you can see what cable goes to the switch then there is no need to bell it out with a multimeter. Often though this is not always possible, or is is more effort than simply belling it out

 

[Meehog]

Thanks. Thought so, it just seemed a bit too simple!

 

[EFLImpudence]

The question normally arises because someone has disconnected all the wires from the ceiling rose without noting which went where - and there could be three, four, five each of reds and blacks (or browns and blues).

It doesn't really matter to you which is the switched live if you connect the new lamp (actual light bulb) to the same terminals as the present one.


Plus, of course, most lofts are stuffed full of insulation and thirty years of rubbish, sorry, family heirlooms.

 

[Meehog]

It doesn't really matter to you which is the switched live if you connect the new lamp (actual light bulb) to the same terminals as the present one.

I can't, I'm replacing the ceiling rose and pendant flex fitting (which only has neutral and live wires) for a fixed light fitting which is connected to the lighting circuit with choccy blocks. Incidentally, are 10 amp teminals high enough or should I go higher?

Cheers,
Phil

 

[EFLImpudence]

5A will do, but may not be physically large enough.

Don't forget the earth connection if it is a class I metal fitting.

Have a look at this thread.
//www.diynot.com/forums/electrics/installing-a-light-fitting.334487/