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I was changing the light switches around the house when I came upon this setup.

The two switches to the right are all wired using the hot wire (black) from the two electrical wire on the back panel. All cold wire (white) are tied together and are left unused.

I am no expert and not even an amateur, but I find this setup strange.

If I change the light switches, should I follow the same connection setup in the picture or try using a standard black-white setup?

The switch on the left (not visible) is a three-way switch.

enter image description here

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1 Answer 1

up vote 11 down vote accepted

Yes, this is normal. There are two ways to wire a two-way switch with 2-core cable like you have:

  • one where the switch is between the supply and the light fixture(s). This is how your switches are wired.

    wiring with light at end of run

    As you can see from the diagram, the white wire is used -- it completes the circuit back to the electrical supply's neutral line.

  • one where the light fixture is between the supply and the switch. I think this is what you mean by a "standard black-white setup".

    wiring with switch at end or run

    Note that the white wire in this case must be marked to indicate that it is carrying the electrical live; I use a small piece of black electrical tape wrapped around the insulation. It's common (in my experience with amateur wiring at least) for this step to be omitted.

(Images found here)

If you change the switches, you should follow the original wiring.

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If you had more than one light it would be like the Christmas tree lights, where on goes out and then all our out until you change the one that's blown. A co-worker took 10 - 12v 25w lamps and wired them in series like this and then plugged it into 120v and they all worked without blowing out. –  lqlarry Dec 4 '11 at 19:40
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The hot is always switched because if the switch were on the neutral, then most of the circuit would always be energized and you would be shocked if you touched the hot even downstream from the switch. –  Steven Dec 4 '11 at 19:55
    
Super, I'll stick to the working schema and simply change the switches. –  Pierre-Alain Vigeant Dec 4 '11 at 20:12

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