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I have a window air conditioner for a room that basically is either on or off. Do you know of a product that I can plug it into that has a thermostat to better control the room's temperature? The thermostat is one of the first forms of automation to find its way into our homes. It is a simple device we take for granted, but in this case, the lack of one is causing the room to be poorly cooled. Once this air conditioner is switched on, it runs continuously until someone turns it off. While it may feel great to enter a 65-degree room when it's in the 90's outdoors, once the electric bill arrives, you'll have a different feeling. Using X10 technology, we can add a sensor to a window air conditioner. The first step is to put an X10 control switch between the air conditioner and the electricity. The X10 unit will turn on and off the power flowing to the air conditioner. As long as the air conditioner is left in the "On" position, it will begin cooling once the X10 module is activated. Depending on the voltage of your air conditioner, you can use one of two simple plug-in modules. Most window air conditioners plug into a regular 120-volt AC outlet, but some need a 240-volt outlet. In any case, we have a plug-in X10 module that can quickly control your window air conditioner. Click to view larger image If your air conditioner runs off 120 volts, use a regular Three-Pin ApplianceLinc Module like the one on the left. This unit plugs into your existing electrical receptacle. It has a socket in the bottom for the AC cord of the air conditioner's to plug into. It can handle up to 15 amps, which should be fine for most modest-sized window air conditioners up to 10,000 BTU's. Still, it's a good idea to look at the ratings label on the air conditioned to make sure the current drawn by it does not exceed 15 amps.
Click to view larger imageIf the air conditioner is a 240-volt model, it will need a different plug-in module. Pictured on the right is a Heavy-Duty 240-Volt Plug-in Appliance Module. Like the 120-volt model, it easily plugs in between the wall outlet and the electrical cord of the air conditioner. We offer two models depending on the amp draw of the unit, 15 or 20 amps. Look carefully at the cord on your air conditioner or the AC outlet it plugs into to match up the proper module. The 20-amp model will fit both 15 and 20 amp cords. Click on the image to see a larger picture of this module.
One note of caution, if you live in an apartment building, you may have three-phase electrical service; the 240-volt plug-in modules won't work. 240-Volt X10 modules won't receive signals properly from the transmitter on three-phase service. 120-volt modules are fine in these homes. Single-family homes have split-single phase electricity and won't be affected by this incompatibility.

To control the plug in module, a transmitter will be needed. What is needed is a device that will send an "ON" signal when the temperature drops below a specified level, called the "set-point". An X10 Powerflash Module #4060 can do this task when attached to a Slimline Temperature Alert Sensor, #7151. The two working together can effectively control the window air conditioner.
Install the Slimline Temperature Alert Sensor on a wall or other flat surface. Connect two small gauge wires on the terminals labeled "Com J1" and "Hi J2". While the sensor is apart, adjust the limits to the temperature set point you would like the air conditioner to start cooling. The other end of the two wires will connect to the screw terminals on the Powerflash Module. Don't worry about the "+" and "-" terminals on the Powerflash, those are for different kinds of signals. Set the house and unit code dials to the same settings as the Appliance Module. The front slide switches on the Powerflash should be set to Input "B" and Mode "3". When the room's temperature exceeds the point you've set, the sensor will close a set of contacts. This will tell the Powerflash module to send an ON signal to the Appliance Module controlling the window air conditioner. When the room cools down and the temperature drops below the set-point, the opposite action will occur: the contacts on the sensor will open, the Powerflash will send an OFF signal, and the Appliance Module will cut off power to the air conditioner.
Click to learn more about the Humidity Sensor There is one more control that might be beneficial. We have all heard that "it's not the heat, it's the humidity" that makes the environment uncomfortable. For those of you who would like a control based upon humidity, substitute the Temperature Sensor with a variable Humidity Sensor, # 7156. Users can dial in a comfortable humidity set point. When the humidity exceeds that point, the air condition will switch on. Once the air conditioner lowers the humidity, the air conditioner will switch off. Click to see a larger imageOne more upgrade for this system I wanted to mention. By adding an X10 Telephone Responder, you can add remote control to the air conditioner. This nifty device plugs a phone jack, much like an answering machine, and allows you to turn X10 devices, like the window air conditioner on and off. Simply call your home and wait for the Telephone Responder to answer, enter a three-digit security code from the tone-tone phone you are calling from. Enter a few more digits and you can command the air conditioner's Appliance Module to come on. This unit will control up to ten X10 modules so you can fire up a hot tub, control lights, or control ANY X10 device. If you would like to learn more about X10 and how it works, click here:

What is X10?

This is a simple project that only requires a screwdriver and a set of wire strippers. Get the whole thing working should take no longer than 15 to 30 minutes. updated 11/06/03