I know this may be a little TOO detailed
One of the neater things I do with X10 is Run my HVAC system with it. I have a custom built thermostat based around a velleman k6002 mashed with the k6003 kit. The thermostat is mounted to the wall in the Living Room on which the other side is the back wall to the Master Bed Room Closet. I opened up the wall in the closet and mounted outlets INSIDE the wall backed up to the stud. There are 4 PowerFlash units in these outlets connected to the Thermostat.
I heat my house in three ways.
Primarily, I built an outdoor wood boiler (actually in my detached shop/garage/barn). This pumps hot water to the house through 1 1/2 inch piping to which I have a manifold in the basement with 5 - 1 inch outputs. There is a master circulation pump in the garage which moves water back and forth, and 5 pumps in the basement which supply hot water to different zones in the house. The manifold in the basement also has a bypass which runs to the water heater supply side to prevent the master circulator pump from over-pressuring in case all 5 zone pumps are off.
The 5 zones are as follows:
Zone 1: Plenum on top of furnace. Like a radiator in the duct work. Furnace fan blows air through it. Supply pump connected to Appliance Module on H 12
Zone 2 : Radiant floor heat in the Living Room and Kitchen. The pump to supply this one is connected to an Appliance Module on H 11
Zone 3 : Radiant floor heat to the Bedroom and Bathroom. The pump to this supply is connected to an Appliance Module on H 10
Zone 4: Radiant floor heat to the Upstairs Bedrooms. The pump to this supply is connected to an Appliance Module on H 9
Zone 5: Radiant floor heat to the Upstairs Common Room and Bathroom. The Pump to this supply is connected to an Appliance Module on H 8
Secondarily, I still have my oil fired furnace in the basement. The thermostat connections have been removed and replaced with an UM506 on H16.
The fan output from the furnace control has a 120v relay attached to it. (when the furnace calls for the fan to come on, it activates the relay) Zone 1 will also activate a relay wired in parallel to it. This allows both Zone 1 and the furnace to use the fan.
As a final reserve, I have electric baseboard heat in the Downstairs Bathroom, Living Room, Upstairs and the Master Bedroom. These are run by Heavy Duty Appliance modules on H1, H2, H3, and H4 respectively.
My primary thermostat runs as follows: At 68 degrees, Zone two is called from a powerflash. If the radiant heat is not enough, at 65 degrees, Zone 1 is called from a powerflash. At 63 degrees, a powerflash calls for the furnace.
The bedroom and two upstairs zones have simple thermostats attached to powerflash units.
Any zone call will active the circulator pump. It also cycles twice per hour to keep the water in the lines warm by a timer in AHP.
The master circulator pump for the wood fired system (in the garage) is on a RR501 on channel H13. In the event that the wood burner hasn't been called for, the pump is activated by a temperature based macro from PC Companion when it's determined to be below 15 degrees outside. This keeps the pump and pipes from freezing. PC Companion samples temperature data from the internet once per hour.
I have a reed switch attached to the level float on my oil tank. It connects to a powerflash on M15. When the fuel gets low, AHP sends me an email, shuts the furnace down after a minute and activates the electric heat. (House Code "M" is monitored on one of my systems) It also activates a .bat file created by X10wavplayer which tells me that we are out of fuel oil and that the emergency electric heat is engaged. This happens on two computers.
X10Dispatcher has listeners set up to tell me when the furnace runs (lets me know that the wood boiler isn't hot enough) between 5:30 am and 11 pm.
In the summertime, I use a combination of window fans and window mounted air conditioners. They all are actived by X10. The air conditioners are called from the thermostat with a little reconfiguation.
Coming up next......X10 around the yard.