A line voltage system is typically only used on heaters and attic fans, but installing a line voltage cooling thermostat should not be any more difficult to handle than simply fitting it to the attic or baseboard. The line voltage single pole system uses power for anything less than 120 volts, while the double pole controls up to 220 volts. The latter will probably be best suited to your air conditioning system. By installing a double pole line voltage cooling thermostat, you can ensure that no power travels to your device except when you decide to turn the thermostat on. You can choose to have the device fitted by a professional, or you may decide that you have enough basic home improvement skills that you can do the job yourself.
Step 1 - The Thermostat
Before you do anything with the thermostat, be sure that the electricity supply is turned off at the main circuit breaker, either in your garage or near the front door of your home. Then, unscrew the back of the thermostat, and look at the screw terminals found inside. These should be labeled Line (for the top terminals) and Load (for the bottom terminals). These screws are affected by whether the thermostat is turned on or not, making contact only when the thermostat is being used.
Step 2 - Remove the Old Thermostat
You will need to remove your old thermostat before you install the new one. Do this by removing the cover using your screwdriver, and then unscrewing the main body of the stat from the wall mount. Take the wires out of the terminals, and then unscrew the mounting plate, ensuring that the wires remain outside the wall. You should then take your new thermostat, and install the wall mounting plate into the same position as the previous one. Push your wires through the hole in the plate, and then screw into the wall.
Step 3 - Wire the Thermostat
You can now wire the new thermostat. Follow the instructions in your manual to locate the right wire for each terminal. Strip a little of the insulation from each wire with wire cutters or pliers. Take care to remove only enough to expose the copper beneath. Undo the terminal you will be using, and then push the wire through the hole. Once the wire is through, tighten the screw until the wire is held firmly in place. You should connect the two wires from the power supply to the terminals marked Line, and the wires supplying the cooling unit with power into the terminals marker Load.
Step 4 - Finish
Once you have wired the thermostat, place the body into the mounting plate, and screw into position. Before you replace the cover, turn the power back on to ensure that the device has been wired correctly, and check that the thermostat will control the AC unit. Once you are satisfied, replace the cover, and leave the line voltage thermostat to do its job.