Two way lighting weirdness

[alchemist]

Was on a job today and was asked to look at why some spotlights upstairs weren't working on the dimmer.

Before I describe it, I just want to say I know there's probably not enough info for someone to tell me what's what, but hoping someone can shed some light on the different methods of achieving two way lighting, as I only know one and what I saw isn't it.

Upstairs: 2 gang dimmer. On the right, the spotlights, on the left, stairway lighting.

Downstairs: 2 gang dimmer, on the left downstairs light, on the right, stairway lighting.

So, when I get there the spots aren't working at all, I take off the faceplate and I see: Left side Common: brown, L1 Black, L2 Grey. But the grey is connected to the other gang on the same switch (I think it was on L2 but it might have been on common.

Downstairs, old colours. Common yellow, L1/L2 red and blue.

I'm going back at some point to try to get it working. I have no idea what the hell is going on with it. Both dimmers do control the stairway lighting, but in a really odd way. On turns it on and off, the other can dim it but only when on at the bottom. The brown and black on the spots doesn't seem to work at all, perhaps it was taking it's live from the other gang -I took the cross link out as it seemed a bit odd.

Is it correct that you can only have one dimmer on controlling a light, is that a regulation?

Any idea how this may have been wired? Could just be the person who did it had no idea what they were doing, or it could be something I've just not seen before.

Thanks in advance.

 

[S60TEM]

seems to me like there could be a junction box joint somewhere as one point has old colours and one point has new and where is the two way lighting taking its feed from? There should really be a switch wire or feed wire in one of the switches too unless someone has done it all at the rose which totally makes the job confusing!

You really need to bell out the circuit to see what is really going on! Oh and as for having the two dimmers.....I didn't think you could have two on the same circuit either as they would work against each other...I might be wrong though?

The way I wire a 2 way switch is........SW1 (feed) Common= black (brown sleeved) L1 = Brown (sw wire feed) + Brown (strapper) L2 = Blue (sw wire return, brown sleeved) + Grey (strapper, brown sleeved) then SW2 same strapper setup as SW1.

 

[batty]

You can only have one dimmer on a single light switching circuit they don't work if you put two. As for the switching sounds like maybe the wires are interconnected between the two switches. I hate it when two way lighting has been wired with joint boxes or at lights it takes ages to sort it out had this the other day on a job but this had a L-E fault managed to sort it out after about three hours.

 

[steptoe]

seems to me like there could be a junction box joint somewhere as one point has old colours and one point has new and where is the two way lighting taking its feed from? There should really be a switch wire or feed wire in one of the switches too unless someone has done it all at the rose which totally makes the job confusing!You really need to bell out the circuit to see what is really going on! Oh and as for having the two dimmers.....I didn't think you could have two on the same circuit either as they would work against each other...I might be wrong though?

The way I wire a 2 way switch is........SW1 (feed) Common= black (brown sleeved) L1 = Brown (sw wire feed) + Brown (strapper) L2 = Blue (sw wire return, brown sleeved) + Grey (strapper, brown sleeved) then SW2 same strapper setup as SW1.

really,

do you want to go through that again.?

Ive gone through it 3 times now and still cant get my head round it,

I have never ever heard of strappers in a 3 core cable, I think you are getting confused with a conventional 2 core strapper system with singles and the newer 3 core method, though it may just be an english terminology thing.

BTW, and its only IMHO , I would have thought brown was the accepted common cable,

 

[Doc Hudson]

Two traditional dimmers cannot be used in a two way switch arrangement, because although you can physical energise or de-energise the lamp with the on/off element, it is impossible to adjust the dimmer setting of the far switch when you are not standing by it. This is not a regulation just a manufacturing design limitation. I suspect one of the dimmers may not be working and someone has already messed around with the wires trying to get it working. It may be easiest to temporary install some standard 2-way switches to get the circuit working before re-instating any dimmers.

Doc H.

 

[alchemist]

really,do you want to go through that again.?

Ive gone through it 3 times now and still cant get my head round it,

I have never ever heard of strappers in a 3 core cable, I think you are getting confused with a conventional 2 core strapper system with singles and the newer 3 core method, though it may just be an english terminology thing.

BTW, and its only IMHO , I would have thought brown was the accepted common cable,

Actually this is the way I was taught to do it to, we were also shown using black as common, although it obviously doesn't matter as long as there is consistency between the two switches.

I think i'm going to change one of the switches to be non dimmable. Then test each core coming into the switch when the downstairs switch is on and off to see what's doing what. I'm not convinced that there are enough cables to make it work but i'll have to do what I can.

 

[S60TEM]

really,do you want to go through that again.?

Ive gone through it 3 times now and still cant get my head round it,

I have never ever heard of strappers in a 3 core cable, I think you are getting confused with a conventional 2 core strapper system with singles and the newer 3 core method, though it may just be an english terminology thing.

BTW, and its only IMHO , I would have thought brown was the accepted common cable,

Yes, really. Remember that when using 3 core and earth for your "strappers" then all the conductors are line conductors and hence all are marked brown so aslong as there is consistency between all two way and or intermediate switches then it doesn't really matter which is the common. I was taught that common practice is black conductor sleeved brown is common.u

 

[septiclecky]

really,do you want to go through that again.?

Ive gone through it 3 times now and still cant get my head round it,

I have never ever heard of strappers in a 3 core cable, I think you are getting confused with a conventional 2 core strapper system with singles and the newer 3 core method, though it may just be an english terminology thing.

BTW, and its only IMHO , I would have thought brown was the accepted common cable,

Think he is talking about where a feed and switch wire comes down from the light to the first switch and by using a 3-core & earth to a second switch you convert it into a 2 way.

 

[S60TEM]

Think he is talking about where a feed and switch wire comes down from the light to the first switch and by using a 3-core & earth to a second switch you convert it into a 2 way.

EXACTLY! lol pardon my literacy skills but i thought I explained it OK.

 

[steptoe]

it must just be an english terminology thing,

I have never heard a 3core described as strappers anywhere else, only ever a 2core.

my mistake..........

obviously,

 

[northernspark]

Yes, really. Remember that when using 3 core and earth for your "strappers" then all the conductors are line conductors and hence all are marked brown so aslong as there is consistency between all two way and or intermediate switches then it doesn't really matter which is the common. I was taught that common practice is black conductor sleeved brown is common.u

Thats a new one on me, always been taught that the brown/red core of your 3 core is the common black/yellow is your L1 along with the perm live and grey/blue is your L2 along with your sw live but I suppose its each to thier own and all that

From what you've said I'd look for a joint box and also check that they havent crossed the strappers over when connecting up, do both dimmers knock the circuit on/off independantly or do you always have to have the down switch on for the up switch to work?