Refinishing my basement and have an open ceiling at the moment. I have hung 12 recessed lights and connected them in 3 groups (groups of 2, 6 and 4 lights) using 14/2. I then ran 14/2 from the start of each group to the entrance to the room where I intend to have 3 separate dimmer switches, one for each group. I also have the power source running to this switch location on 14/2. I have run 3 sets of 14/3 wire between from this location to another location where I intend to have a 2nd set of dimmer switches further into the room.
I have only tried hooking up one set of lights to for testing purposes and can't get both dimmers to work. Tried using a diagram that was shown on here (http://www.buildmyowncabin.com/electrical/3-way-switch-diagram-7.pdf) but it did not work. Could not even get lights to come on.
I also found a diagram that has power at one dimmer and the lights at the other but not both power and lights from the same dimmer and ran a temp power line to the 2nd dimmer but even though the likes worked from either switch the dimmers did not work. http://www.do-it-yourself-help.com/3_way_switch_wiring.html ( the diagram with 2 dimmers)
Best Answer
As @Tester101 says, with conventional dimmers, you can only have one dimmer in a circuit if the fixture (or set of fixtures) is being controlled from more than one location.
If you are switching from two locations, you also need to use 3-way switches for both the plain switches and dimmers (many dimmers are 3-way compatible).
There are specialized dimmers that work as master and slave units. These do allow dimming from multiple locations, but you need to use a set of matched units. These are also much more costly than basic 3-way dimmers.
Finally, if you are running remote switches that only connect back to the first set of switches, you need x/4 cable, not x/3. Two wires serve as travelers, one as the common return and one as neutral. While not every switch requires a neutral, code now requires it as a hedge against future active devices. If you do not need the neutral, simply cap it in the box.