Changing a 2 way 2 switch to a 2 way 3 switch box


Postby carpsid » Mon Jun 16, 2008 10:44 pm

I have an existing 2 switch 2 way light switch that operates the Hall light and the upstairs landing light too -- I want to add an exterior security light by changing this to a 2 way three switch system that would work as it is now for upstairs/downstairs operation and the third switch to switch on/off the exterior light but i'm not 100% on best way of fitting the wiring to the the new switch.

Any advice much appreciated thanks

Sid
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Postby ericmark » Tue Jun 17, 2008 12:34 pm

Your problem will be there is normally no neutral at the switch. Normally outside lights do not have a junction box built in and switch boxes tend to be rather shallow with very little room for connector blocks. If you use a junction box it needs to be accessible. So the first job is to decide what to use as a junction box. I have seen people just use connector strip and shove it into the ceiling but I could not recommend that sort of method as someone lifting floor boards in the future could touch the connections. A more professional method would be to use a socket backing box with a blanking plate on it. But until one sees the job one can’t really advise on best method it needs some common sense. Once you have selected how and where to locate a junction box you take a full supply to box and connect the switch and outside light in the same way as wiring a normal ceiling rose.
There are so may variables in how the job can be done it is really impossible to give any more help at this stage.
One point I will make though is to make sure there is an earth available it was common in the past not to take earths to lighting so I always check the earth loop impedance before taking power to outside lights.
From the 1st July you will need to also use an earth leakage trip and for outside lights it would make sense also with outside lights there is always a risk of water ingress and taking the feed from a power circuit using a switched fused spur unit has a lot of advantages in that the neutral is available and if a fault occurs it is easy to remove the fuse so everything else can continue to work without the outside light.
Not sure if this answers your question feel free to ask again if not.
Eric
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Postby carpsid » Fri Jun 20, 2008 4:51 pm

Am i to understand then that if a tap into the existing Live & neutral from the lights connecting to the Switch now and run the link to a Junction box that is fused, then run the wires for the outside light from that?

This will mean i then won't need the three switches on the faceplate i've bought, but, can stay with the existing two switch faceplate and use a switch fused Junction box -- am i correct or completely off the mark?
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Postby ericmark » Fri Jun 20, 2008 11:32 pm

I have read and re-read and can't quite work out what you are doing.
If from power circuit a switched fused spur will do the job.
If from lights a switch and junction box is required but will come from ceiling rose not tapped into to any existing wires in the switch.

To clarify each switch on the switch plate will have it's own feed and return. Three switches have three cables.

In the case of an outside lamp rather than doing cable joint in lamp as it would be done for internal lamps it needs to be done inside the house either in switch backing box or some other junction box exactly how will depend on exactly what you already have and how much space there is to work in.
ericmark

Postby carpsid » Sun Dec 14, 2008 5:06 pm

Eric

Kept meaning to reply and somehow it always got forgotten.

Anyway, if you are still out there, thanks for the help you, gave it did point me in the right direction, in that it caused me to re-track how i had done the circuit. As it happened i had tapped from the wrong part of the ceiling rose into a junction box. I fitted a new Junction box onto the ceiling joists, as i had to leave the other in place now i had fitted it!!!and ran the new connection to the light -- it now works.

I had taken the feed from the wrong cable in the Ceiling rose - i hadn't taken it from the Loop!!!!

Thanks again
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