Three two way switches on a single lighting circuit


Postby AndyInShropshire » Fri Jan 11, 2008 6:18 pm

I'm hoping someone can help me out with the last bit of this as the trusty Readers Digest book has taken me so far and then abandoned me for the last step.

We've one lighting circuit on the landing which is controlled by three two-way switches, one at the foot of the stairs (which we'll call S1) one half way along the landing (S2) and and one at the far end of the landing (S3).

The power comes into the circuit at S3 where I have the incoming red and the outgoing yellow connected to L1, the incoming black and the outgoing blue connected to L2 and the outgoing red connected to Common.

The other end of the circuit at S1 I have a yellow connected to L1, a blue connected to L2 and the red connected to Common.

Both of these work as expected and turn the light on and off quite happily from both ends.

When we replaced the switch in the middle (S2) however, it originally had a strange design with 4 connectors rather than the more traditional three with only the yellow and blue cables hooked into the switch and the two red ones connected together with a spare bit of terminal block!

The new switch is the same as the other two and just has L1, L2 and Common.

So given that I'm clearly just connecting together two sets of red/blue/yellow cables, which go to which terminal? The RD book doesn't help and my attempts to work it out logically have thus far come to nothing, and I've been trying to avoid the temptation to do it by trial and error !

Any suggestions gratefully received.

Andy
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Postby rflight » Fri Jan 11, 2008 10:36 pm

What your talking about is an intermediate switch. Any two way switch circuit will have two (three terminal switches marked com, L1, L2) at either end of the circuit and any switch in between these two will have to be an[b] intermediate [/b]switch (four terminals marked L1, L2 and L1,L2)

The intermediate switch is connected across the strappers of the two way circuit, i.e. two strappers into one pair of L1 and L2 and the other two strappers into the other L1 and L2. Hope this is making sense.

Your description of the connections does'nt sound quite right, but there are some good drawings here that might explain things a little better. See if any of this makes sense and let us know how you get on or if you need more help.

http://www.the50plus.co.uk/tech_support ... lights.pdf :lol:
Last edited by rflight on Sat Jan 12, 2008 7:18 am, edited 1 time in total.
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Postby kuzz » Fri Jan 11, 2008 10:36 pm

You need an intermediate switch in the middle (the 4 connection type). A 2way switch toggles the common between l1 & l2. An intermediate switch is different as it crosses the strappers.
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Postby 333rocky333 » Fri Jan 11, 2008 10:43 pm

You need to change s2 you have brought wrong switch, take the three term 2 way switch back and get a four term INTERMEDIATE SWITCH

On this connect yell and blue of one cable to L1 in and L2 in ,
also connect other yell and blue of other cable to L1 and L2 out , this switch just switches across that pair either straight or diagonally.
The two reds still join together safely in a connecter block, but are seperate and not connected to the switch.

Till you get the switch just link all three each colour to same colour and use other two 2 way switches.
OR refit the old one same as above

ALL THE WIRES are live in the 3 switches even the black and blue ones.

To help you understand, at S3 your red is the power in and the black is the power out to the light the power just goes back and forth via R Y B wires depending on switch position.
There is no neutral this is taken to the light from elsewhere


ISOLATE SUPPLY FIRST

ERICMARK has a link to a wiring diagram of this if you still get stuck .
He may drop by soon
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Postby ericmark » Sat Jan 12, 2008 2:30 am

I did make up the circuit and posted it on my website to help but is seems I am not allowed to put a link on this forum. Sorry about that.

Eric
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Postby ericmark » Sat Jan 12, 2008 10:09 am

Hi since most web sites start www and mine uses same name as used here and is on talktalk who's web sites end with net you may find it. But the intermediate switch is normally shown as four terminals with cross between them since I was using a program to simulate I have to use proper switch diagram which shows how they are interconnected inside the switch. You can use an intermediate as a two way switch which ever terminal you pick as common you ignore the terminal next to it. Where one switch plate has two or more switches and one is intermediate then this is only way to wire other switches in the same block. I remember at about 12 years old seeing on in my uncles house and trying to work out how it was done. My school teacher could not help took ages for me to find out no internet in 1964 so I fully understand your problem. I hope it is now solved.

All best ericmark
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Postby rflight » Sat Jan 12, 2008 1:45 pm

Did try to steer the op to the projects page but felt the link i posted with simple diagrams would explain things better. :)
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Postby AndyInShropshire » Sun Jan 13, 2008 8:56 pm

Thank you all very much. Clearly starting with the right type of switch would be an excellent start...

I've got one on order and I'll give this a go (with the power isolated) when it arrives.

Cheers all

Andy
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