I just had our house re-wired (by a professional, not myself). I'm looking into replacing a light switch with a fancy programmable version (Honeywell Econoswitch RPLS740B).
The location for the switch has two switches next to each other in the same box. They both have two black wires and and one bare copper wire ground connected to them. There is a bundle of 2 white wires nutted together behind the switches not connected to anything.
When I look at the manual for the programmable switch, it has three connections: black, blue (load), and white (neutral).
So my questions:
For the black wires connected to the current switch, how do I know which is hot, and which is the heading off to the light (load)? Does it matter?
For the white, do I just un-nut one of the wires behind the switches and hook it up?
Why does the programmable switch require the white wire?