Lighting circuit

[doog442]

A friend called me around today. He's disconnected a light fitting to fit a new one without noting where any of the wires went (honestly not me I learnt that mistake years ago) I took this pic on arrival.

I've identified the neutral on the cable on the left (1) as being the switched live but am just wondering if I was missing something with the connections in the photo ...ie the switched live connected to the two lives on the middle and right.

I was intending to connect the switched live to the Live on the new light via a new wire, join the two neutrals (on middle and right) and connect to Neutral on new light, join the three Lives in a block on their own.

cheers

 

[EFLImpudence]

I've identified the neutral on the cable on the left (1) as being the switched live

No, you have identified the black wire on the left as the switch cable.

Therefore - IF it is a usual loop in/loop out circuit and not another light connected to this one - the other two will be actual neutrals.

but am just wondering if I was missing something with the connections in the photo ...ie the switched live connected to the two lives on the middle and right.

It would appear that someone has connected the switch cable the other way round from usual.
That is the black to the Live and the red being the switched live returning from the switch.
As you will note this makes it obvious which is the switch cable.

I was intending to connect the switched live to the Live on the new light via a new wire

join the two neutrals (on middle and right) and connect to Neutral on new light,

join the three Lives in a block on their own.

Correct.

 

[pete01]

You've got it

Left single red L
2 red 1 black loop (not connected to light)
2 x black N
3 earth to metal casing.

 

[doog442]

No, you have identified the black wire on the left as the switch cable.

View attachment 307089

Therefore - IF it is a usual loop in/loop out circuit and not another light connected to this one - the other two will be actual neutrals.


It would appear that someone has connected the switch cable the other way round from usual.
That is the black to the Live and the red being the switched live returning from the switch.
As you will note this makes it obvious which is the switch cable.




Correct.

Thanks but now I'm confused following the post above....so having separated the wires do I proceed as you agreed was the correct course of action that I mentioned...or revert back to the original photo as per the post above (single red to L, two black to N and black switch plus two red to loop not connected )

Cheers

 

[FrodoOne]

Nomenclature is (or should be) significant!

The initial photo shows three cables, labeled "1", "2" and "3".

doog442 asserts that "I've identified the neutral on the cable on the left (1) as being the switched live"
(which should have been written as "Switched Line")
Hence, one or other of cables "2" and "3" must come from the Supply and the (remaining) "other" goes to one or more other "Light Fittings".

EFLImpudence then wrote

No, you have identified the black wire on the left as the switch cable.

However, a "wire" is not (necessarily) a "cable" - unless it is a single wire (double insulated) within a "cable"!
(The [Twin and Earth] cable [1] on the Left is [presumably] a "Switched Loop" cable.)

A "convention" is that, in a "Switched Loop", the Black (insulated) wire should be the "Line" conductor, with the "Switched Line" conductor being the Red (insulated) - returning - conductor
and
that the Black (insulated) conductor should be re-designated with "Tape", "Shrink Tubing" or other such "Permanent Marking".

If doog442 is correct,
the Red insulated conductors of cables "2" and "3" should be joined together - together with the re-designated Black (insulated) wire of cable "1".
The Black insulated conductors of cables 2" and "3" should be joined together and connected to the "Neutral" connection of the new Light Fitting.
The Red insulated conductor of the "Switched Loop" cable "1" should connect to the "Line" of the new "Light Fitting".

(All "Earth" conductors should be "joined", including any/that of the Light Fitting..)

 

[doog442]

Nomenclature is (or should be) significant!

The initial photo shows three cables, labeled "1", "2" and "3".

doog442 asserts that "I've identified the neutral on the cable on the left (1) as being the switched live"
(which should have been written as "Switched Line")
Hence, one or other of cables "2" and "3" must come from the Supply and the (remaining) "other" goes to one or more other "Light Fittings".

EFLImpudence then wrote

However, a "wire" is not (necessarily) a "cable" - unless it is a single wire (double insulated) within a "cable"!
(The [Twin and Earth] cable [1] on the Left is [presumably] a "Switched Loop" cable.)

A "convention" is that, in a "Switched Loop", the Black (insulated) wire should be the "Line" conductor, with the "Switched Line" conductor being the Red (insulated) - returning - conductor
and
that the Black (insulated) conductor should be re-designated with "Tape", "Shrink Tubing" or other such "Permanent Marking".

If doog442 is correct,
the Red insulated conductors of cables "2" and "3" should be joined together - together with the re-designated Black (insulated) wire of cable "1".
The Black insulated conductors of cables 2" and "3" should be joined together and connected to the "Neutral" connection of the new Light Fitting.
The Red insulated conductor of the "Switched Loop" cable "1" should connect to the "Line" of the new "Light Fitting".

(All "Earth" conductors should be "joined", including any/that of the Light Fitting..)

Thanks for that. So as per post #3 ?

 

[SUNRAY]

Thanks for that. So as per post #3 ?

Yes and exactly as it appears in post #1 too.

Including red sleeve to indicate use other than neutral.

It would also be perfectly acceptable for cable '1' to be wired; red = loop & black = SL (sleeved red or otherwise marked to indicate a line live conductor.

 

[doog442]

Yes and exactly as it appears in post #1 too.
View attachment 307122
Including red sleeve to indicate use other than neutral.

It would also be perfectly acceptable for cable '1' to be wired; red = loop & black = SL (sleeved red or otherwise marked to indicate a line live conductor.

That's brilliant, much appreciated.

 

[EFLImpudence]

However, a "wire" is not (necessarily) a "cable" - unless it is a single wire (double insulated) within a "cable"!

Neither Doog nor I said it was.

Doog said: "I've identified the neutral on the cable on the left (1)" which, apart from writing 'neutral' instead of 'black' was correct.

A "convention" is that, in a "Switched Loop", the Black (insulated) wire should be the "Line" conductor, with the "Switched Line" conductor being the Red (insulated) - returning - conductor

That is the situation in this example but it is rare in the UK for it to be wired like that so not a convention.

 

[ebee]

Neither Doog nor I said it was.

Doog said: "I've identified the neutral on the cable on the left (1)" which, apart from writing 'neutral' instead of 'black' was correct.


That is the situation in this example but it is rare in the UK for it to be wired like that so not a convention.

it is usually tother way round - the Red (would be the Perm L and the Black would be the SL but it really should be sleeved red) of course that was in the days of proper colours before all the brown black grey fiasco

 

[SUNRAY]

That is the situation in this example but it is rare in the UK for it to be wired like that so not a convention.

I wouldn't describe it as rare, It was quite popular a few years back especially when harmonised first appeared. If I had to put a figure on it I'd say I probably see around 5-10%

 

[EFLImpudence]

I wouldn't describe it as rare, It was quite popular a few years back especially when harmonised first appeared. If I had to put a figure on it I'd say I probably see around 5-10%

 

[ebee]

no not a convention

 

[SUNRAY]

View attachment 307136
View attachment 307134

In which case I'd not describe as rare. To me rare is something I'd be surprised to find.

On one housing estate I know, the convention (I assume either a consultants or the contractors standard) was red as SL and black as loop. In that situation what most of us would consider 'standard' or 'conventional' was actually the rarity. I say was as over the years where much work has been done it may have reached 50;50.

 

[EFLImpudence]

Ok. From 5/10%. Do I have any advance on 50%?


See if you can find a number of images of roses wired like that.