Switch Live

[GRAHAM LISH]

I have 2 red joined in terminal 2 earth 2 black but not any tape on either of the black wires, i have a multimeter so electric off black probe on earth wire then test each black with red probe with switch in the on position.
meter on the alarm mode

am i correct or just thinking i am

many thanks for any help

 

[opps]

Sorry, I don't quite follow what you are saying. Why do you expect any of the wires to have tape on them.

 

[EFLImpudence]

To indicate that a black wire is the switched live.


Graham: Where are you testing? At the ceiling rose?

 

[GRAHAM LISH]

firstly i meant a sleeve to indicate the switch live wire and secondly yes i am testing at the ceiling rose

 

[terryplumb]

With power off ,and circuit proved dead,do continuity testing to establish which is the switch cable.

 

[GRAHAM LISH]

black lead on earth cable, then test each of the black wires for a beep reaction with the red cable in its simplest terms, or am i getting that wrong

 

[terryplumb]

You test continuity between the red and black of each cable. One cable is the circuits live and neutral ,the other is the switch cable.
The switch cable would show continuity / or no continuity as switch is operated.( Continuity when switch is ON ,and no continuity when switch is off.
The other cable would not have the alternating results when switch is operated.
Isolating the power and testing for dead before testing.

 

[GRAHAM LISH]

both red live wires are together in a terminal block, leaving two black wires without an identifying sleeve as to which is the switch live, so testing between red and black is not possible, can i just put one probe(black) on the earth wire and use the red probe to test which one is the switch live, so sorry to be such a idiot, two wires, just need to know which one, then whole thing can be wired safely.

 

[terryplumb]

You can do it that way ,but you would need to be measuring voltages ,on a live circuit ,with your meter set on AC voltage range, NOT on a continuity setting.
Are you competent to do that ,safely,on a live circuit ?

 

[GRAHAM LISH]

not really, live testing not for me, guess its electrician time, better safe than sorry, thanks too all anyway

 

[RandomGrinch]

Hi,

testing between red and black is not possible

Why not?
You said your multimeter has an 'alarm' mode - does the alarm sound if the two probes are connected?
If so, that is 'continuity mode' and exactly what we need.
It is far safer to test the circuits with the power off.
Your red wires are almost definitely lives. Hold the red probe of your multimeter to the red wires in the terminal block.
Hold the black probe to one of the black wires.
If the alarm sounds and then when you flip the switch, doesn't sound, that is your switched live.
...and repeat with other black wire!

Simple!

If you still can't get anywhere, send us some photos of the ceiling rose and behind the switch.

 

[terryplumb]

It's simple to do the continuity test as I outlined earlier, with power off.

 

[RandomGrinch]

It's simple to do the continuity test as I outlined earlier, with power off.

Yes, sorry, I meant to acknowledge your post, I just tried to explain in a different way

 

[terryplumb]

Hi,

Why not?
You said your multimeter has an 'alarm' mode - does the alarm sound if the two probes are connected?
If so, that is 'continuity mode' and exactly what we need.
It is far safer to test the circuits with the power off.
Your red wires are almost definitely lives. Hold the red probe of your multimeter to the red wires in the terminal block.
Hold the black probe to one of the black wires.
If the alarm sounds, that is your switched live, if it doesn't, flip the switch and see if it sounds.
If it still doesn't sound, repeat the above with the other black wire.

Simple!

If you still can't get anywhere, send us some photos of the ceiling rose and behind the switch.

Part of the above isn't quite correct RandomGrinch. Live to neutral would likely result in continuity.

 

[RandomGrinch]

Part of the above isn't quite correct RandomGrinch. Live to neutral would likely result in continuity.

Thanks, yes I was rushing - I've edited the post.