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adding a new light and switch from a current light switch

Postby tcc » Wed Dec 10, 2008 9:35 pm

I am installing a light new light and switch from a current light switch because i cant access the wiring near the rose.
Basically i have run the wiring from the current light switch to the new light switch and then to the outside light but when the current inside light is on the outside light go's out and vice versa.
Is there some wiring to sort this out or something available to break the switching circuit and make use of the power supply so both lights can work independantly?
From what i have read i know this is wrong, cant be done or not a good idea but can it be done?
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Postby sparx » Wed Dec 10, 2008 9:43 pm

Probably can't be done as usually no neutral only Live in & sw-line out,
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Postby tcc » Wed Dec 10, 2008 9:55 pm

What about if i just left it for the time being?
When the new switch is on the outside light comes on and the toilet light go's off and vice versa. When the new switch is off the toilet light works as normal and the outside light wont work.
This will do until i can get access to the ceiling rose but is it safe with the wiring?
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Postby ericmark » Thu Dec 11, 2008 6:06 pm

Except where extra low voltage lighting was fitted from new light switches rarely have a neutral connection.
To fit outside lights as an add on normally one would connect to the power circuit.
Because 5 amp is normally the max one can supply to lights when supplying from a socket normally we use either a switched fuse connection unit (FCU) or a grid switch the latter will allow fitting a fuse unit as one of it’s options.
Also since socket supplies are normally already RCD protected one does not have to use Ali-tube cable or install an RCD. But when taking a supply from a lighting circuit because of the change in regulations often it will also involve either use of Ali-tube cable or fitting a RCD to protect the new installation which is not so easy when taking the supply from a ceiling rose.
Even if the existing sockets are not RCD protected it is relatively easy to install a RCD fused connection unit at the origin of the additional circuitry.
As to wiring in series as I think you are talking about I would consider this as dangerous and would advise against it although not against BS7671
I will also point out Parts P and L1 the latter requires outside lights should not exceed 150 watt and must auto switch off when not required or be of a type that only lamps at 40 lumens per watt or better can be used. And except when there is no external junction boxes etc etc it can also come under Part P.
I would agree in most cases you would likely not get caught but if the outside lamp was to upset a neighbours then it may cause problems or if you try to sell the house.

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