2 Way Switch Problem


Postby Stillia » Tue Dec 16, 2008 10:44 pm

Wondered if someone can help....
Tried to change an old two way switch to a new switch & got mixed up with the wiring.
At the bottom switch, it has an old 3 core cable with red in common, blue in L1 & yellow in L2.
I mirrored this upstairs in the new switch, but I also have a T&E cable (red & black) in there, which I assumed was the switch cable.
The trouble is, no matter where I put this red & black cable it does not seem to work!
I can switch on & off at both downstairs and up, but cannot switch one from the other!
I've also belled out the switch cable to the fitting & it's not the same cable (assuming junction box somewhere in unaccessible loft).
Can anyone offer advice, as its doing my box in!!!

Thanks, A
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Postby ericmark » Wed Dec 17, 2008 1:50 am

I am not really sure what the problem is?
“I can switch on & off at both downstairs and up, but cannot switch one from the other!”
I guess you have up-stairs and down-stairs lights which will only work from one switch? There are two main ways to wire two way switches with the preferred method the connections for the switch wires are different than for a on/off switch.
If the switch is marked com + L1 and L2 the switch wires for on/off would be com and L1 but for a two way switch it would be L1 and L2 and yes connections between both switches is like for like.
I have tried to explain on my web site http://www.ericpalmer.fsnet.co.uk/Lighting.html at the bottom I have some drawing of a switch the switch wires to light on a two way switch should be terminals 1 and 2 as shown in the drawing.
Does this help?
Eric
ericmark

Postby Stillia » Wed Dec 17, 2008 7:19 am

Hi Eric, thanks for your reply.

Referring to my previous email, there is only 1 light affected by this & this is at the top of the stairs. The 2 way switch at the bottom of the stairs is part of a 3 gang switch & is marked Com, L1 & L2, whilst the new switch I have for the top is marked Com, 1way & 2way. Does the wording make any difference?

As i said, I can switch the light on and off at the bottom & also on & off at the top. However, when its switched on from one end, I cannot switch it off from the other.

I hope this makes more sense?

Thanks, Andy.
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Postby ericmark » Wed Dec 17, 2008 12:32 pm

I will guess only one wire wrong!
One switch will have two wires in two of the three holes. Neither of these should be the com only L1 or L2 should have two wires in it.
To recap one cable with three wires will go into same whole in both switches in real terms as long as the wire which goes into com down stairs goes to com up stairs the other two being swapped will not matter.
One switch will also have a second cable with two wires the two wires go to L1 and L2
NOT COM
As to marking on switch as long as COM is correct the others don't really matter. Since both switches use the word COM then not real problem.
Looking at http://upload.wikimedia.org/wikipedia/c ... tching.PNG we are following No2 method and No3 shows what COM is and why that is only terminal which must be right.
Ignore diagram 1 as to use that you would need terminal block in light switch so very rarely used.
Eric
ericmark

Postby Stillia » Wed Dec 17, 2008 5:11 pm

Thanks for that Eric............
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