Wiring a 2 Way Light Switch
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Joined: Wed Dec 17, 2008 11:02 am

Wiring a 2 Way Light Switch

by Tobester » Wed Dec 17, 2008 11:04 am


New here and hope somebody can help me, just reassurance really. I am trying to replace a 2 way light switch with a new dimmer switch. I know where all the wires go apart from the fact that the current bridging wire is not long enough. Do I just get a replacement wire from some 3 core cable and make it up myself?


by ericmark » Thu Dec 18, 2008 3:44 pm

Your post rings alarm bells. Many years ago it was common to use two core cable between a pair of two way switches and use a live supply from another switch in the same switch plate. This however had two major problems.

The first to be recognised was interference because the twin core cable only carried current in one direction it radiated power like a radio aerial and TV's Radio's Cordless Phones and even wired phones can pick up the mains hum.

Second more recent is although if both switches come of same supply fuse/MCB there may be no problem it is now common to split up and down stairs lighting and using two core cable will result in borrowed neutrals which is dangerous.

Using a dimmer switch will likely make the first problem a lot worse with 1st 2nd 3rd harmonics being generated what they are does not really matter except they can cause even more interference.

I will guess it is OK to make up your own link wire but be aware of likely problems. And remember I am using a little guess work so may be wrong.


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