DIY Doctor

3 Way lighting?

Postby ken.wells » Sat Nov 15, 2008 4:33 pm

I have been told that in addition to the normal 2 way light switches it is possible to use a "Transfer switch" to allow a third switch in the circuit. I did ask how it worked, as I couldn't readily see how it could, and was told that the transfer switch forms a "X" when switched. Does anybody know if this is true? I've not seen "Transfer" switches in any books or stores. :?:
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Postby matthewm1965 » Sat Nov 15, 2008 6:44 pm

The other more common name for them is an "intermediate" switch.
They are available from most electrical stores but not always in the likes of B&Q.
They work by effectively crossing over the two switch wires.
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Postby sparx » Sat Nov 15, 2008 9:55 pm

they are called intermediate switches, & have 4 terminals. You can have as many as you want, each switch reversing the last action.

I once had to install a circuit which had 2 staircases leading to a gallery in a semicircle with 8 bedrooms leading off. This meant a 2way switch at the bottom of each staircase & an int. sw. in between each door, some 11 switches in all anyone of which could turn a central chandalier on or off.

This was presented to me as a challenge in my first apprenticeship year!!!

The switches do indeed cross over the 2 strappers in a 2way circuit.

In one position the top 2 terms connect to the bottom 2 ie top left to bottom left, top right to bottom right.
in the other position they connect top L to bottom R, top R to bottom L.

To understand it more look at a 2 way switch circuit, at a point between the 2 switches there are the 2 strappers going from L2 to L2 & L1 to L1, plus possibly a wire between both Com. terms which is left untouched.

cutting the 2 strappers will give 4 ends. From one switch pair put to top terms. on sw. from other pair put to bottom terms. this can be repeated for more switches if desired, trace circuit with all combinations,..
It works!!!!
sorry if long winded but you asked!
regards Sparx
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Postby ken.wells » Sun Nov 16, 2008 9:31 am

Thank you, not long winded at all. Informative is the word! I feel reasonbly confident to be able to wire in the switches, after some scribbling on paper of course.
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