Originally Posted by emstype
I have a 220v line that runs to the end of a dock (it runs a boat lift). I would like to put a 110v light out there as well. Can I take one leg of the 220v and use it to run the 110v light? The boat lift and the light will not be on at the same time.
You can only do this if it's a 4-wire circuit, i.e. there's a neutral wire present. Otherwise no. If there is no neutral, then you have two options for installing a light: either use a small transformer to step 240V down to 120 to run the light, or use a 240V light. If you use a fluorescent, metal halide, or sodium fixture, you can easily choose one with a 240V ballast. That's the simplest solution.