12:04PM | 04/27/09
Member Since: 04/26/09
1 lifetime posts
I have a 3-gang box, and I'm interested in combining 2 of the existing single-pole light switches in the box into 1 switch (that controls both lights simultaneously). My reason for doing this is because I want to install an in-wall timer (such as this:,

and I want the timer to control both lights simultaneously (same on and off times). I'd rather not have to purchase 2 timers, and the box itself does not have room for 2 bulky timers anyways.

My thoughts are to pigtail 2 wires from each switch together, and connect each combined pair to the timer, as in the attached diagram (wire colours are only used to identify wires in the diagram). The result would the 2 switches replaced by 1 timer and 1 blank in the box. Does this make sense, and are there any caveats or things I should watch out for?
8603 combining 2 switches

doug seibert

06:52PM | 04/27/09
Member Since: 08/10/02
842 lifetime posts
Of course the lights would need to be on the same circuit......

"......measure Once.....cut Twice....

throw that one away and cut a new one...."


02:17PM | 04/28/09
Member Since: 01/09/07
198 lifetime posts
The 2 incoming wires to the switches should probably NOT be connected together, unless they both go back to the same breaker in the panel.

If they go to different breakers, they may be on different phases -- you will find that out soon enough, because there will be 240V between them, and the breakers will blow immediately once you power this on. Even if they are on the same phase, you will still have 2 different breakers feeding power to this timer switch. That is a possibly dangerous situation, because you need to turn off BOTH breakers to kill power to this. Someone could think it is safe to work on this, when it is still powered from the other breaker.

Either verify that both incoming power wires come from the same breaker, or choose one to use and deadend the other with a wire nut.


04:54AM | 05/03/09
Member Since: 03/30/09
4 lifetime posts
What you're trying to do can be done. How you do it depends on what you have. It may help to simplify it and only use one of the power wires instead of both for the reasons given in the previous replies.

I've found Intermatic in-wall timers to have a high failure rate, so good luck with that.
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