Strange One

Lucien Nunes · May 1, 2016

If you think about these two options and the one RB describes as a logical truth-table, you will see that no matter how stupidly it is wired, they are the only possibilities for S1 gang 2 if it actually does something. The specially-controlled light can either be forced off (RB's scheme); on (my first scheme); or to the opposite state to the 2-way (my second scheme*). The only remaining possibility is to force it to the same state in which case the switch does nothing at all.

* strictly speaking a variant of this scheme, using an intermediate as S1 gang 1, with the 2-way light teed into one outgoing strapper so that it functions as 2-way with S2, but both strappers continuing to a 2-way switch as gang 2 with the light fed from the common. Then, both gangs of S1 control the special light, gang 1 as 2-way with S2, gang 2 then selects 'same or different' to the 2-way light. Yes you would need a grid switch, no it's not very sensible!

Lucien Nunes · May 1, 2016

Simples!

hightower · May 3, 2016

Lucien Nunes said:
* strictly speaking a variant of this scheme, using an intermediate as S1 gang 1, with the 2-way light teed into one outgoing strapper so that it functions as 2-way with S2, but both strappers continuing to a 2-way switch as gang 2 with the light fed from the common. Then, both gangs of S1 control the special light, gang 1 as 2-way with S2, gang 2 then selects 'same or different' to the 2-way light. Yes you would need a grid switch, no it's not very sensible!

I've tried drawing this out but it's giving me a headache - I don't suppose you (or anyone else) can draw it to help me get my head around the logic?

Thanks,

andyb · May 3, 2016

Unless I've totally miss read this thread (not unusual for me) it looks to me like a simple switching arrangment.
The 2 core at the 1 gang will be a live and switch return, so l1 and l2, the 3 core goes to one of the switches at the 2 gang. The 2 core at the 1 gang is a live and switch return for the other switch.

Sent from my SM-T700 using Tapatalk

andyb · May 3, 2016

Just re read the op on my pc not my tablet. I had misunderstood the problem.

My guess is now that the owner is confused and it never worked as described.

Lucien Nunes · May 3, 2016

I think that too, but there are various ways that it might have been wired and I've sketched the permutations below. SL1 is always ordinary 2-way and SL2 is also controlled independently in various gimmicky ways - I'm not saying any of them are particularly useful or sensible. Obviously the PL & SL might have been taken to different ends compared to how I've shown them.

Now we get to the question - What do they want it to do and can we arrange it with the available cables?

GEOFF S · May 3, 2016

hightower said:
Bit of a strange one.

2 pendants that (apparently) used to work as such until one of the switches was rewired by a friend of theirs:

Switch 1, 2 gang
Switch 2, 1 gang

Switch 2 and one of the gangs of Switch 1 work in tandem to create 2-way lighting. Either switch turns BOTH lights on and off, as standard two way. The remaining gang on Switch 1 turns ONE of the lights on and off independently.

Now, I think she's getting her wires crossed somewhere, I'm going to draw it out when I get in later on but I can't see it working from what I can map out in my mind. I think maybe 1 of the lights worked on a 1-way switch, and the other light worked on a 2-way switch. This is in a living room, so I wonder if it's an old dining room knocked through.

Just thought I'd ask for thoughts before I get in and have chance to draw it out. At both switches there are 5 cores - a 3 core and a 2 core each. My guess is Switch 2 has the 2 core as the feed and the 3 core as the strappers, going to the 3 core at switch 1, and feeding one light. Then the remaining 2 core at switch 1 will be a switch drop for the other light.

Will get a chance to test it properly sometime and figure out what goes where, but can't stop thinking about it for now.

Hi

Maybe it was wired as a two way, the switched live supplied the first pendent and then looped through the switch then onto the second pendent, this would give you the option of both lights on and the ability to switch one off.

Cheers

hightower · May 3, 2016

Lucien Nunes said:
Now we get to the question - What do they want it to do and can we arrange it with the available cables?

Hopefully this helps explain things - this is how it's currently wired, a straight forward 2-way switch for one light, and a 1-way switch for the other. Each box has a 2-core and a 3-core entering. Now, apparently this used to be wired (many moons ago) so that S1 could individually control both lights (as it can wired like this), but rather than S2 only turning on/off the right hand light it should turn on/off both.

Now, I haven't done any circuit design yet as part of college, but I can join the dots and as far as I can work out, RB is correct when he says to achieve something like this you would need to introduce electronic components etc

Richard Burns · May 3, 2016

Lucien Nunes said:
I think that too, but there are various ways that it might have been wired and I've sketched the permutations below. SL1 is always ordinary 2-way and SL2 is also controlled independently in various gimmicky ways - I'm not saying any of them are particularly useful or sensible. Obviously the PL & SL might have been taken to different ends compared to how I've shown them.

I love the split two way, that would cause major headaches!!

Strange One

Lucien Nunes

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Lucien Nunes

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hightower

andyb

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andyb

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Lucien Nunes

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GEOFF S

hightower

Richard Burns

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