If you want to install a thermostat, here's what you need to know. Follow these easy steps to install a thermostat in your home:
1. Turn Off Power to the HVAC System:
Turn off the power for your heating and air conditioning system at the main service panel. Its circuit breaker should be clearly labeled.
Safety Tip: Make sure you don't install a new thermostat on circuits exceeding the manufacturer-specified voltage. Higher voltage thermostat wiring will damage the controls and may cause shock or become a fire hazard. Additionally, short or incorrect thermostat wiring will damage the unit and may cause personal injury and/or property damage.
2. Remove Existing Thermostat:
Remove the old thermostat cover plate with a screwdriver. Unscrew the thermostat mounting screws and remove the thermostat body.
3. Separate & Label Wires:
Label the wires using masking tape so you can remember their screw-terminal locations. There is no standard color code, so use letter codes to make the wires easy to identify. Disconnect the wires. Tape the wires to the wall or wrap them around a pencil to prevent them from slipping into the wall cavity.
4. Install a C-wire if Needed:
Install a C-Wire if Needed: Smart thermostats can have up to five thermostat wires that always include a “common wire” or C-wire. The C-wire provides a continuous flow of power to the thermostat without necessarily turning your other appliances (such as the fan or cooling) on or off.
If you’re replacing a smart thermostat with another smart thermostat, you’ll already have a C-wire connected to the C terminal. If you’re upgrading to a smart thermostat, you’ll need to find and identify the C-wire or install a new C-wire.
Even if your old thermostat was not using a C-wire, an unused C-wire may be stuffed in the wall behind the thermostat’s backplate. Check your HVAC control board to see if it has a wire connected to its C terminal. The HVAC control board is usually located near the heating and air conditioning system or inside of a furnace access panel. If it has a C-wire, the other end of the wire should be in the wall, and you can use it for your new smart thermostat.
If there is no C-wire, one option is to use an “add-a-wire" kit or a power extender kit. Some smart thermostat models may come with this kit and other thermostat parts included. Follow the manufacturer's instructions for installing this kit at the HVAC control board. Another option is to use a 24-volt adapter that provides a C-wire and plugs into a nearby outlet to power your thermostat.
If your HVAC control board has an empty C terminal, you can also install a C-wire yourself and run it through the walls to your thermostat. If you’re ever in doubt, call an electrician to add a C-wire for you.
5. Install the New Thermostat and Wire:
Remove the existing thermostat base by loosening the mounting screws. Separate the front of the new thermostat from the base. Begin by installing the base first. Thread the low-voltage wires through the specified opening of the new thermostat base. If your new thermostat is not self-leveling, use a small level to make sure it's properly aligned. Mount the thermostat base on the wall using the screws included with the thermostat. Connect the low-voltage wires to the appropriate screw terminals on the new thermostat base. If your connections do not match, consult the installation diagram in the new thermostat's owner's manual. Tighten any loose wire connections and make sure the wires and sheathing are in good condition. Install the battery or batteries in the thermostat body (if applicable). Make sure the battery size and polarity are both correct.
