I am fitting a new light. I am changing an existing lighgswitch from one gang to two, then leading a second?

Question

I am fitting a new light pendant in a place where there has not been a light before. I am changing an existing one gang lightswitch to a 2 gang, then leading an extra cable from that switch to a junction box, then to a ceiling rose, & then to the new light fitment. The switch doesn't seem to like this & does not want to recognise the original & new light fitments as two indepently functioning lights with two separate switches - why? what can I do about this?

Answer 1

What you are trying to install a correspondence or a double switch block?



I think that you are trying to service two light from the same position, using a double switch block.

OK in the box behind the switch from where the wires are connected to the switch. In the single switch mode the live is connected to one of the switch's two terminals, this should be connected to the off position side.

The other wire is connected to the other side so when you through the switch the power is shunted to the output terminal and the light goes on.

To change this so that a second switch can be use in the same block you must check, has the switch an "internal connection" to check this you wire up the switch and check that there's power on both outputs and that they function independent of each other, power off, power on 1 and 2. If this is correct and the power is switch independently of each-other, to the two light outlets, then you have forgotten to run a negative line to the new light outlet or it's not connected properly. If the double switch has "no" internal connection then you will have to shunt the power to it's inlet using a short piece of wire.



You can see on the diagram from Tony the double switch Shunt

Answer 2

I'll get you a drawing. Be back in a few minutes.



The drawing below shows the modern method for wiring a light. Notice the neutral is present inside the switch box. That's important. If you have the "Interrupt" method then you don't have a neutral present in the box. Even if it's a white wire, it's not functioning as a neutral.



THAT may be the reason you're not getting the results you want. If that's the case then you will have to rewire both the original as well as adding in the modifications.



The mod's shows a jumper between switches on one side. The other side of each switch goes to separate lights, whatever route you take through the walls and ceilings.



Also understand that in the interrupt method, it didn't matter which wire was switched, hot or neutral. In my drawing I show the hot being switched, but there have been plenty plenty plenty of times I've seen the neutral being switched. Back when this was a common method it didn't matter. All you were doing was interrupting the circuit. It's been a big pain for many DIY homeowners who wanted to rewire something.



Hope this helps.



Happy Holidays.



'')

Answer 3

When I say red, it might be brown and when I say black, it might be blue. (UK only) The existing 1 gang switch has a red and black wire. The red wire should be the live one - test it. Connect a short piece of wire from the red terminal to the opposite terminal on the other gang. Connect a wire from the remaining terminal to the new ceiling rose. You will now have separate power for the new light fitting. You now need to install a neutral wire from the new ceiling rose to the junction box. (don't forget the earths) The new light will now work independantly but will not be part of the loop (ring main) so you cannot use too much wattage.