I have a 3 way hard wired switch for a whole house fan that I want to replace with non dimming X10 switches. (I do know and accept the X10 reliability factors)
The existing switch has 3 positions HI SPEED | OFF | LOW SPEED. It is wired 1 wire to power (high) 1 wire to motor Low, 1 wire to motor Hi. The motor has 3 wires; Hi speed, Low speed Neutral.
I am thinking I can replace this with 2 separate non dimming X10 switches. The 1st would be a ON | OFF toggle style switch, that would connect the power (hi) to the common contact of the second switch, a non dimming 2 way ON | ON toggle style switch. One of the 2 switched contacts to be connected to the motor Hi, and the other switched contact to be connected to motor Low.
I would mount both switches side by side with the ON | OFF switch to the left and the HI | LOW to the right for best natural action. One of my major complaints with the existing switch is that the center OFF is easy to miss if you are in a hurry, and strangers will almost always use the WRONG position for the HI / LOW speed. If I mount the switch upside down we all seem to pick the WRONG one. Using a separate switch (UP for HI | DOWN for LOW) makes sense from the way that other switches generally work.
Eventually I intend to use a computer and utilize the X10 control features to turn a fan on conditionally when the inside temperature exceeds the outside temperature and the inside temperature exceeds a predetermined TARGET-TEMP value. The fan would always turn on to the LOW speed condition, but then if the outside temperature exceeds a predetermined USE_MAX_FAN parameter after 30 seconds the second switch would be set to the HIGH speed position. In all cases the turn off command would reset the speed to LOW.
The fan manufacturer specifies that the fan be started at low speed, but the supplied switch doesn't force that, and you can see considerable arcing in the switch if you start it in the high speed position (easy to do this).