I’m perplexed.  I just installed a fantech fan in my bathroom.  I got the grilles with the integral light and purchased a timer switch to go along with it.  The switch is designed to turn off the lights when thrown but allow the fan to run for a preset extended period of time.  What I don’t understand is that the switch has a white “common” wire coming out of it.  There is the standard black “hot” leg running into the switch with a blue “light” and red “fan” leg coming out of the switch along with the white.  The wiring diagram shows the hot leg in and out to the respective destinations with the white connected to the common.  I always run my switches remotely with the black in and the white taped black back to the fixture.  What gives with a “common” coming out of this switch?