Replacing a two gang switch with a three gang and new light?

W

willj23

Hi all,
Firstly i apologise for my lack of terminology here! I currently have two lights in my garage that are controlled by a two gang light switch that controls each light separately.

What i am trying to do is add a new light to the circuit (hoping to add a security light). I have bought a 3 gang light switch and 1.0mm 3 core flex cable for the new light.
I am having trouble wiring in the new light as you may have gathered. I have attached a few pics of the existing wiring and one for the back of the new switch.

Out of the three cable in the 2nd picture, the one of the far right is the main power cable. The other two are attached to the existing lights.

Any help would be greatly appreciated!! I hope ive supplied enough information!

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You need to link all the common terminals together using short pieces of wire and then to the live supply, as you can see has been done on the original switch wiring. All neutrals then need to go to the terminal block with the black wires, all earths linked together in another terminal block with green/yellow sleeving, and individual switched lives to each light will come from L1 (1 way) on their respective switch.
 
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Your existing switch hasn't been wired quite right so that may be confusing you.

The feed wire seems to go into L1 and then to COM

Strictly speaking the feeds should go to the COM terminals and the switched outputs to the various lights will connect to the L1 terminals.

Hope that makes sense..
 
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I wonder how those cables are fixed?

All 3 edge-on under a single large clip?
 
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Strictly speaking the feeds should go to the COM terminals and the switched outputs to the various lights will connect to the L1 terminals..
Any particular reason for this? i've always wired switches whichever way round makes the wiring easier myself.
 
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yes, so that if you happen to want to use the L2 terminal for something ( br it 2 way switching using the old 2 plate method, or perhaps turning an outside light on when you turn the garage lights off ) then it won't work since the live will be on the wrong terminal.
 
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yes, so that if you happen to want to use the L2 terminal for something ( br it 2 way switching using the old 2 plate method
But if i'm adding two way switching to a light that currently has one way switching by running a new cable to a new switch i'm not going to be using the old "two plate" method.

or perhaps turning an outside light on when you turn the garage lights off ) then it won't work since the live will be on the wrong terminal.
I find this a pretty unlikely scenario since it would remove my ability to have both off or both on.
 
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you can't say for certain that you'll never use 2 plate..
it may be a long corridor with lots of lights.. wired in trunking and conduit..
you run 2 strappers from the switch to the new one, take the switch wire out and run a switch wire from the new switch at the far end to the nearest light..
saves on volt drop from the strappers..
 
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Equally though the new switch might be further from the light than the old in a similar conduit/trunking system so you would go for two plate but in that case the original switch would have it's output taken from the com.

So modifications to turn a one way system into a two way do not seem to favour wiring the one way switch either way round over the other. and personally I think it's a lot neater to have the permanent live running along one end of a row of switches than zigzaging all over the place.
 
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I wasn't criticsising the wiring method, I was just trying to clarify to the OP as he seemed to be confused by what he has found.

Just as a point of order, when I was messing around with complex relay switchery, with a changeover contact it was 'best practise' to put the supply on the common thus allowing the NO and NC contacts to be 0 or 1 depending on function.
 
W

willj23

You need to link all the common terminals together using short pieces of wire and then to the live supply, as you can see has been done on the original switch wiring. All neutrals then need to go to the terminal block with the black wires, all earths linked together in another terminal block with green/yellow sleeving, and individual switched lives to each light will come from L1 (1 way) on their respective switch.

I have just tried wiring it up and have got it working :D Thank you very much for your input it was of major use! I found the suggest to link all of the common terminals together the key, i didnt do that before, and now i have it works fine.

Thanks again!
 

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