On 1/11/2013 12:48 PM, gary wrote:
I need electricity for a ceiling fan. In my attic, I found an existing wire that powers a light switch. I want to run a new wire from the existing wire to the ceiling fan. How do I tap into the existing wire?

You need to read the electrical code in your jurisdiction, wherever that is.
Tapping into a wire is trivial. Making it pass inspection may take more
knowledge
than you currently possess. And the thing that trips you up will
seem trivial or even stupid.

A lot depends on your definition of "ceiling fan".

My neighbor came home with a ceiling fan...the bladed
decapitation type.
I read the instructions and suggested he take it back.

According to the instructions, you can't install the fan
into an existing box in the ceiling. You need a box
approved for ceiling fan use. Near as I could tell,
the approved box differed in three areas.
It had a sticker that said, "approved for ceiling fan use".
And a price sticker with a substantially higher price.
And it required opening the ceiling and patching it back up.

He wasn't gonna get a permit or have it inspected. I didn't
want to be party to denial of a fire insurance claim.

This stuff is easy and you can always get away with it...until
you get caught with your house on fire.

Funny story...
About 50 years ago, there was some problem with the window
air conditioner. It got unplugged.
Dad had difficulty getting the plug back into the wall,
but made it happen.
Next day, I was riding my bike home from school.
"Cool, look at all the fire trucks!"
Imagine how my mood changed when I discovered it was MY house.
Point being, simple stuff can cause BIG problems.

And that wasn't the last time I got burned out of my house.
But that's a funny story for a different day.