Lighting Puzzle

[Bernster]

The 3 cables are connected via connector blocks as follows:

• 
  The black wires from the 2 white cables (assumed supply) connected to the blue wire of the switch cable.
  The red wires from the 2 white cables connected to the brown wire of the switch cable

Any pointers as to how this works or was intended to be configured to supply the pendant light ?

Red wires should be your live loop in terminal block.
Black wires should be your neutral loop in terminal block.
Earth wires should be your earth loop in terminal block.

Assuming your dimmer has been wired as normal ie red in C and black(with red sleeve) in L1 then...
At the ceiling
Your switch (red) should be connected to the live loop terminal block- this will take the power down to your switch.
At the ceiling
Your switch wire black(with red sleeve) bringing the power up from the switch should be wired to the brown in the pendant. The returning blue wire from the pendeant should be wired to the neutral loop block. Any earth should be wired to the earth block.

Thank you Riveralt,

that made sense and was exactly the solution.

I should have mentioned that the earth is present and connected in all cases as the switch and lights are metal cased.

Based on above I tried this and it works:

 

[Chri5]

It would.

You diagram is a bit sloppy in as much as the switched live from lamp (with the red marker on it) looks as if it's going to earth.

As it works that obviously isn't the case, it goes to the black L1 at the switch.

Look at the on site Wiki, electrics- UK - Lighting, it will show you better diagram methods should you ever need them.

 

[ban-all-sheds]

I checked and one of the 2 white cables and the top one in the diagram is live feed, the bottom one is not so assume is supply to the 6 down lights.

OK - lets go with that for a moment.

The only way that could work, and not have the downlights on all the time (as long as the switch is off) and then nothing on because of a popped breaker (and probably a permanently wrecked dimmer) is if the blacks in those cables are not neutrals.

If they are then what your diagram shows is the downlights permanently connected to L&N via the top two connector blocks, and a switch across the same two blocks which will create an instant short circuit as soon as it's turned on.

Neither of those things are happening, so the blacks cannot be neutrals. In effect the two white T/E cables could be switch drops, with both permanent lives commoned (maybe as a result of earlier mods, where two individually switched lights were combined?).

But those lights are getting their neutrals from somewhere else, as the ones in those white cables cannot be neutrals.

And yet...

That cannot be right.

What do you think would happen if you took that top white cable and joined the red and black together and turned the power on?

Obviously you haven't actually got lights behaving oddly and breakers tripping and switches getting wrecked.

But another thing you obviously don't have is what you've drawn.

 

[Bernster]

Hi bAS,

Told you it was a puzzle, I can confirm that what is in my diagram is what is in place both before and now. I accept that it looks wrong and that the functions of various wires might not match their colours.

I suspect that it may be tied into what is in the adjacent room as the wiring in that double switch consists of 4 drop cables with all the brown wires feeding into the switch terminals and the 4 blue wires into a terminal block together.

Question for you smart people is how can I test this setup to confirm what is in place is OK and understood for future reference ?

PS. In case anyone was wondering, the work was done by a certified electrician and I have Part P certificate and building regs sign-off. I would get the electrician back but that is not an option for reasons I cannot share.

 

[Chri5]

Have you learned the metholodgy of circuit design via the wiki ?

Once you have done that Luke, you will feel the force.


Don't go killing yourself, but you need to investigate and you need to understand what your looking at. The wiring diagrams in the wiki are as simple as Forest Gump.

Look at then, look at the work done at home, and if you can't work it out or have any doubts post, or post pictures. I can help- but I can't guess

 

[Bernster]

Have you learned the metholodgy of circuit design via the wiki ?

Once you have done that Luke, you will feel the force.


Don't go killing yourself, but you need to investigate and you need to understand what your looking at. The wiring diagrams in the wiki are as simple as Forest Gump.

Look at then, look at the work done at home, and if you can't work it out or have any doubts post, or post pictures. I can help- but I can't guess

Point taken

I will assemble something ala Wiki examples and cone back for more wisdom.

And advice on drawing package ti use ? I have Microsoft Visio and it's a bit of a pig for this.

 

[RF Lighting]

Most of the drawings in the wiki were done by Spark123 or me and we used MS paint.

 

[ban-all-sheds]

The force is weak in that tool.

I generally find Powerpoint to do the trick.

 

[mfarrow]

The only way that could work, and not have the downlights on all the time (as long as the switch is off) and then nothing on because of a popped breaker (and probably a permanently wrecked dimmer) is if the blacks in those cables are not neutrals.

If they are then what your diagram shows is the downlights permanently connected to L&N via the top two connector blocks

Neither of those things are happening, so the blacks cannot be neutrals. In effect the two white T/E cables could be switch drops.

But those lights are getting their neutrals from somewhere else, as the ones in those white cables cannot be neutrals.

And yet...

That cannot be right.

BAS, I think the answer is simple.

The three white cables are what the diagrams say they are, being loop in-out and central pendant switch.

But I think the grey cable is mis-diagnosed, and probably feeds a junction box for the LV downlights, which then feeds another grey cable for the switch.

Of course, the OP hasn't said any testing has been undertaken to verify this, so we're just going on where the OP thinks the grey cable goes. But I think this sounds more plausible than a heap of mods.

 

[ban-all-sheds]

Good point, well made.

 

[Bernster]

Gents,

took on board the diagram tips, stuck with Visio as I know how to use it even though it is not easiest to use for this.

I had mistakenly assumed the grey cable was to the switch which confused me and everyone else. Well done mfarrow for working out my mistake.

Anyway, Have re-drawn what is in place in the act of 'closure' to try and at least clarify what is in place:

 

[ban-all-sheds]

stuck with Visio as I know how to use it even though it is not easiest to use for this.

It produces nice results though.

Feel free to get stuck into some of the tattier scribbles in the Wiki and replace them with shiny new ones