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I recently tried to replace my light switch with some smart switches but when I open it, the wiring was a bit odd to me.

The top of wire of the first switch was piggy tailed/connected to the bottom of the second light switch. Is that correct?

I have included pictures and a bad hand drawn picture. enter image description hereenter image description hereenter image description hereenter image description here

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    Note that with wiring that old, you want to move everything as little as possible. That insulation will crack pretty easily leading to possible shorts. – JPhi1618 Oct 23 '17 at 18:55
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That is a perfectly functional way of splitting a single hot (highlighted green in your sketch) to supply power to two separate switched fixtures. However, most smart switches require a neutral conductor in the switch box so there can be an always-on connection for the "smart" circuitry.

It's hard to tell whether or not you have this because all of your conductors have the same color insulation. It looks like knob and tube wiring, so there is a distinct possibility of the neutral not being present in the switch box. In older circuitry it wasn't uncommon for the installer to run hot to fixtures via one path and return the neutral to the fuse/breaker panel via a completely different route.

  • Thanks! So its normal to run the hot to the bottom? Would it not make more sense to connect it to the top? Any suggestions on how to wire it? – Dan Oct 23 '17 at 15:32
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    Well, each switch just creates a break in the line when it's off. So it'll work in either configuration. But for consistency it would make sense to have both switches line/load configured the same way. There shouldn't really be more than one conductor per terminal either, so the best way to tidy this up would be to add two pigtails to the line (power in) with a wire nut and connect the other end of each one to its own switch, on the top terminal for each. – CactusCake Oct 23 '17 at 15:46
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    The tradition is to feed the top of the switch. It is an extension of feeding the top of a disconnect for equipment. However, it is not a Code requirement so it is your choice. – ArchonOSX Oct 23 '17 at 16:27
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    The requirement to have a neutral wire for a switch wasn't introduced until 2011 (I think?), so unless the house is pretty new, chances of having a neutral there is just luck. – JPhi1618 Oct 23 '17 at 19:00
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With simple switches, the tops and bottoms are interchangeable. It will be more logical to you if you swap terminals on one of the switches, so the always-hots are serving e.g. the top of the switch, and the switched-hot serves the bottoms of each switch.

Once you make that logical "shift", this is fairly easy to understand, and very normal and proper way to wire, provided the neutrals to both lamps return to the same neutral.

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This was permitted by older codes. It's not now. Pigtails joined in a wire nut should be used to connect a single wire to multiple terminals.

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