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BarneyN

Two-way wiring

Question

BarneyN

I want to install two off two-way lighting switches, one at each end of a long building, with two (or more) lights in between. Supply is at one end, near one of the switch positions. All wiring will be done with single-core cabling in plastic conduit. As I understand normal two-way switching, the supply is usually taken to a ceiling rose and then to the switches, whereas I would prefer to go supply -> switch -> light -> light -> switch. I think that one way of doing this would be to connect the supply to L1 and L2 of the first switch, strap the two switches' L1s together and L2s likewise, and then run cable from the first switch's COM to one side of the first light and on to the second, while having the other switch's COM feeding the other side of each light.

 

Is that OK (on paper it works for me) ? If so, are there any standards for the colours of cables I should use to minimise confusion in years to come ? Any better way of doing it ?

 

 

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Evans Electric

Hi  Barney ,  I think I can see see where you are going with this .

 

So:-  

1)  Run 20mm PVC conduit  from one end to the other  with a "Through" box  at  each light position .   If they are fluorescent type LEDs Battens  , put two boxes at  600 centres.

2) Conduit down to switches  and back to the board .   Wire  a traditional 2 way  with a L at one end ...a switched wire  from the other and two strappers in between .

3)   Use single insul .cable  6491X not domestic cable .  1.5mm   all lives brown    / neutral Blue  / earth G/Yell    .

 

4)  I didn't understand your wiring description  so do this  :-  Live  to switch near board  in "C"  Common .... strappers in L1 &L2  at both ends ...a Switch wire from last switch "C" 

        to loop between the lights  .     The Blue neutral from the board to light  (1)  & loop to light (2)   Loop the  Earth to every point . 

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Geoff1946

Hi Barney,   If I've understood your wiring description correctly it's a definite NO_NO!

 

I think you are suggesting putting the two strappers between the switches onto the supply with the lamps connected between the two switch commons.  Is that what you mean?

If so, don't do it.  When the lamps are OFF, it's because both lamp terminals are on neutral OR both on live.    In the latter condition it's potentially lethal to a lamp changer. 

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Andy™

so as above, switching neutrals. whilst it may work and function, its wrong and potentially dangerous in that it can be 'off' yet still live enough to kill you

 

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Murdoch

OP - you are over complicating matters ....... just following wiring guides readily available .......... and don't go light to light with the 2 way switching and strappers ... these only need to go switch to switch

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BarneyN

Thanks all for the prompt responses, and yes (Geoff and Andy) I can see the potentially fatal error of my ways in having one or other of the wires at the lights always live - so I'll not do it that way !  Murdoch - I cannot find a wiring guide which does not take the supply to the lamp (/ceiling rose) first.

 

Deke - thanks, that looks good. Is there any way of embedding a schematic or image into a forum post to check my understanding ?

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BarneyN

And I should have said - yes, 20mm round conduit, through boxes at each light, 1.5mm 6491X cable, earth to every point.

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Andy™
Just now, BarneyN said:

Thanks all for the prompt responses, and yes (Geoff and Andy) I can see the potentially fatal error of my ways in having one or other of the wires at the lights always live - so I'll not do it that way !  Murdoch - I cannot find a wiring guide which does not take the supply to the lamp (/ceiling rose) first.

 

Deke - thanks, that looks good. Is there any way of embedding a schematic or image into a forum post to check my understanding ?

 

simple - run a neutral alongside the strappers. youd still need the same number of cores as you proposed, just instead of linking commons, the 3rd core is the neutral (well, 4 core, since youll need a cpc)

 

what tranining / qualifications do you have?

Edited by Andy™

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BarneyN

 

16 hours ago, Andy™ said:

 

simple - run a neutral alongside the strappers. youd still need the same number of cores as you proposed, just instead of linking commons, the 3rd core is the neutral (well, 4 core, since youll need a cpc)

 

Thanks - so like the first diagram in http://www.lightwiring.co.uk/tag/2-way-switch-wiring-diagram/ - except that the Neutral does not go back through the switches as shown, but runs with the strappers.

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