Before installing your thermostat, consider its location carefully. Thermostat should be located away from drafts, vents, sunlight, doorways, skylights, lamps, windows… Sources of heat and cooling are a common cause of false readings, affecting the performance of the heating or cooling equipment.
Read the manufacturer's installation instructions. They too can help prevent some "ghost" readings and unnecessary cycling of the HVAC equipment.
Easy vs. difficult installation
Though simple and usually safe, installation should be done properly.
Otherwise you risk damaging not only the thermostat but also the heating or cooling equipment.Installation is safe and simple or only moderately difficult; thermostats use low-voltage wiring, and replacing a thermostat with a new one can be fairly straightforward.
Things are more tricky when installing a new thermostat, or when things are more than just replacing... In these cases, unless you are a skilled DIY, it’s better to call an electrician.
Also consider calling a HVAC contractor or an electrician to install thermostats for electric baseboard systems. It involves high-voltage wiring, making the installation unsafe.
Also take into consideration the manufacturer's recommendations. Honeywell, for instance, requires professional installation for their more expensive thermostats. Warranties depend on it.
Installing a thermostat
Follow these steps to replace a thermostat, after reading the manufacturer’s instructions and checking the compatibility of the device with your furnace, heat pump or air conditioner…
- Turn off the electric power at the main switch.
- Remove the existing thermostat from the wall; there may be two pieces, one of which screwed to the wall.
- Study carefully the screws and wires of the existing thermostat; note the screws/wires and their colors, letters, numbers… Mark each wire of the existing thermostat, using a piece of tape or something similar; record the information on them.
- Inspect the new thermostat, and make sure you know where to attach the wires; if you aren't certain, call an electrician.
- Attach the wire to the new thermostat according to the information that you have recorded, and fasten the thermostat to the wall.