How do I combine lights on single pole switch with lights on 3-way switch?

I have a room with two sets of lights. One set is controlled by a single pole switch. The other set is on a three way switch. How do I combine them so that all the lights are controlled by the 3-way switches?
Conveniently, the single pole and one of the three way switches are double-ganged in the same switch box.
Also I have power from different circuits running to each of switch boxes (one is for the single, the other is for the three-way).
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@gmail.com wrote:

Assuming the circuit powering the three-way lights has sufficient ampacity to safely handle adding the "other" lights and whatever else may be on that circuit, the job could be either very easy or a real PIA, depending on how lucky you are with how the job was originally wired.
What I'd do is connect a test lamp between the arm of the three-way switch and the neutral of that circuit and see if that test lamp goes on and off with the existing three-way lights when either switch is operated.
If it does, you're in luck, and all you'd have to do is move the switched lead from the single pole switch (feeding it's lamps) to the arm of the three-way switch and move the neutral going to the lamps from it's present connection to the neutral of the circuit feeding the three-way lamps.
If the test lamp doesn't follow the present three-way lights, but stays on all the time, chances are you're SOL unless you're willing to to pull some new leads. And that's likely what you'll find if the power for that three-way circuit enters the box those switches are in.
Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat \'57 EE)
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 24 Apr 2008 13:36:56 -0400, Jeff Wisnia

If they lights are on separate circuits you would have to use a relay
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 24 Apr 2008 15:33:55 -0500, Buy1get1free

That should read...
If "them" lights are on separate circuits you would have to use a relay :)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.