I have kitchen lights with a dimmer switch that I want to "tap into" to make a second switch to operate separately, lights over an island. In the wall are two big wires (aluminum by the way). One of them has a black, a white, and red wire and a green (ground?). The other just has a black a white and a ground. There were some connections in the back of the box like a white to a white and a black pigtail. I just couldn't figure out what that was all about, but later realized that a) this configuration goes on to fire the lights in the livingroom and the light over the sink (which works separatetly from the kitchen lights) and b) two circuit breakers are involved - not just one. By testing with my light bulb and alligators, I think that both the red and the white in the four wire trunk are both hots, and presume that the black one is a common.

However, I cannot figure out how to wire this. I have a wire leaving this box to go to the box I am installing to fire the lights over the island. How do I wire this to a) get the kitchen lights to work and the living room lights to work (not switched here, of course) and get juice to the switch in the box to the island. Am I missing something here? So far, I can only get the kitchen lights to work OR the living room lights to work but not both, even with both circuit breakers on.

BE VERY CREFUL HERE!

If two circuit breakers are involved then this is a Multiwire branch circuit and you have to very careful with the "Neutral" wire (white). This wire is shared by both breakers and if it opens, you will effectively put 240 volts instead of 120 volts on the circuit.

Take a look at the breakers again, you should see a black conductor on one and a red conductor on the other. Each conductor is a branch circuit and the Neutral (return) is used by both branches.

First determine which circuit is the feed for your lights, then determine is a switch loop was used to feed the dimmer switch.

If there is a switch loop, you will see a supply circuit for the lights in the ceiling either a black/white with ground or a red/white. Off that there will be a black white cable or a black white red going to the switch box. The cable will depend on whether the Neutral was brought to the dimmer switch or not.

If it is a simple switch loop, then you should see a white conductor connected to either the black or red supply. That conductor is feed to the switch. The black (if it is a simple loop) will be the return to the light. If there is a three conductor feed, then the Black will feed the switch, red will be the return to the light and white will be capped off or used by the dimmer switch.

In order to add a second switch, you will need to use a three way switches. A simple snap switch cannot be used to control lights from two separate locations.

Thank you for the prompt and detailed response to my question. I guess the first sentence wasn't worded accurately. I want to essentially tap into one or the other of these circuits to separately fire the lites over the island, with its own switch (so I can operate the kitchen lites and / or the island lites entirely separately each with their own switches). Whoever owned this place had lots of electrical work done but never separated lighting over the island from lighting in the kitchen. Drat. So basically I want to create a new branch to one or the other of these circuits, entirely separate from the kitchen lights.

I looked in the panel and found a red and a black wire entering (in the same hole) and a black wire entering separately on the top of what is two tiers of circuit breakers which are stuck together, one over the other and of course the white wires installed on the sides. Because the red and black are in the same hole, I can't tell from this which breaker is which or why there are two wires on one pole. The living rooom circuits have a white and a black. So... I presume that this red wired red/black/white trunk must be the hot (red) going to the kitchen lites, right? (I can't see the kitchen light boxes directly as these are pot lites with tracks installed over them). So, in this case, is it possible to know from what I can see, how how does that (kitchen light) circuit work?

BTW, I have noticed that the previously working bulbs in the track lites are either burned out or are blinky (those eco fluorescent spots) so I might have inadvertently give them 220... could that have happened? Could this be a polarity issue?

You reall do not need to pull an entirely new branch circuit just to separate out the island lights.

What you need to do is remove the conductor to the island lights from the switched leg for the entire kitchen. At the supply for the kitchen lights, connect a new cable from the main feed to the island, At the island, create a new switch loop to control the island lights.