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 Toller 01-06-2013 12:06 PM

Confused by my 3way switch

I have two 3way switches controlling a pole light.
I want to replace one switch with a 2way timer switch, and short the other one out. We have never used the second switch, so there is nothing lost.

Looking at the first switch, there are 3 terminals; the common is always 121v. With the switch down, and the light off, the first traveler is 0 and the other is 121v. With the switch up, and the light on, the first traveler is 121v and the second is 45v.

I don't understand what is going on. I presume the 45v with the light on is voltage drop over the light, but if it is 0/121 with the switch down, shouldn't it be 45/0 with the switch up, instead of 121/45 as it actually is?

There is another 3way switch next to it for a different light, and it is the same (only 73v instead of 45v).

This simply isn't doing what I would have expected. Can you explain it to me

 rjniles 01-06-2013 01:22 PM

The odd voltagesa being back fed from the load. Ignore them they are meaningless.

At the second switch connect one of the traveler wires to the wire an the common. Note the color of the traveler. Insulate the othe traveler wit a wire nut. Cover the box with a blank.
At the first box connect the timer to the traveler from the second box (by color) and the wire on the common. Insulate the other traveler. If your timer needs a neutral, hopefully there is one in the box.

 Toller 01-06-2013 05:09 PM

All done, works great. Is the mysterious voltage because the travelers run together and the one with real voltage induces a little voltage in the other one?

It is an interesting switch. It has a calendar and clock and knows when sunset is, so it can turn the light on accordingly. Or at least that is what they say.

 kbsparky 01-06-2013 05:12 PM

Persactly. Induced, or phantom voltage due to a non-connected wire being adjacent to a hot line in the same cable/conduit.

Cap `em off and ignore `em.

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