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Once you’ve bought a good programmable thermostat you are faced with the challenge of installation. While most people manage to install their new programmable thermostat without problem there are those who don’t follow the instruction manual properly and give themselves a nasty shock or blow the transformer.

The first thing to do is to read the manual that came with the programmable thermostat carefully. The information given below is generalized and suitable for most programmable thermostats, although not all. For example, Honeywell warn you not to follow the color code used by the wall wires.

Next you should turn off the air-con and heat unit at the circuit breaker. To check that they are off, turn on the old thermostat. If you don’t turn them off you can make the costly mistake of blowing the transformer.

Once you are satisfied the HVAC is off, take the cover off the old thermostat and check the heat anticipator setting. You might have to set the new thermostat to the same setting, although most programmable thermostats do this automatically.

Then unscrew the old thermostat from its sub-base. You should see a number of colored wires going to terminals on the old thermostat. The wires should be red, green, yellow and white. They should be attached to terminals of the same color. If the wires don’t have colors than use masking tape to mark the wires correctly according to the terminals on the old thermostat – i.e. if a wire is going to the red terminal then that must be marked as the ‘red’ wire. Note that red is the source ‘hot’ wire from the transformer.

Once you are certain about the identities of the wires (don’t worry if there are extra wires coming from the wall that are not being used), then you can unscrew the wires from the old thermostat. As you remove each wire wrap it around a pencil so as to stop it disappearing back into the wall hole.

Remove the old sub-base and drill holes for the new sub-base. Some programmable thermostats come with a drill bit for the holes. If not then use a drill bit that is smaller than the anchor holes.

Then put the wires from the wall through the new sub-base and screw the new sub-base to the wall. Make sure the new sub-base is level with a spirit level. Once satisfied with the installation of the new sub-base then attach the wires to the new thermostat – red to red, yellow to yellow, green to green and white to white. Red is the source wire, green is the fan, yellow is the air conditioner and white is the heat. Red on the programmable thermostat is sometimes marked RH or RC. Make sure the live wires touch nothing but the terminals they are intended for.

Once done you can attach the new programmable thermostat to the sub-base and check that the anticipator setting is the same as with the old thermostat. Then attach the front cover to the thermostat and turn the power back on. Press reset on the programmable thermostat and then test the heating, air-con and fan separately to make sure they are all working. If so, you are ready to input your programs and you are ready to be more energy efficient.

Links for Online Instruction Manuals for Programmable Thermostats

Honeywell RTH8500D | Honeywell RTH7500D | Honeywell RTH7600D | Honeywell THX9321R5000 | VisionPro
Lux Products TX9000TS | Lux Products TX9100E | Lux Products TX1500E | Lux Products HP2110
Hunter 44550 | Hunter 44860

More Programmable Thermostat Resources

Energy Star Recommended Settings

Review of Honeywell RTH7500D | Review of Honeywell RTH8500D | Review of Lux Products TX1500E | Review of Lux Products TX9000TS | Honeywell RTH7500D vs Lux Products TX1500E | More About Honeywell International