Replacing your old Thermostat with a new Thermostat
Do I need an electrician to replace a thermostat? If your current thermostat uses batteries no, it’s an easy DIY project.
Can I replace a mechanical thermostat with a Digital? In most cases Yes, they are more efficient.
Selecting the Best thermostat for your heating system. Send us a photo of your old Thermostat or/and a photo of the wiring at the back.
2 Wire Thermostat System (millivolt system) HEAT + FAN only
- A 2-wire thermostat is for Ducted heat or Hot water only.
- Controlled by a battery powered digital thermostat.
- The two wires most often used are red for power and white for heat.
- Connected to terminals W & R or COM & NO
3 Wire Thermostat System HEAT +FAN only
- Controlled by a battery (backup) or a 24Vac powered digital thermostat
- The configurations will include a White wire, a 24-volt Common wire, and a 24-volt Red wire.
- Connected to terminals W & R & C
4 Wire Thermostat System HEAT +FAN only or FAN only
- Controlled by a battery (backup) or a 24Vac powered digital thermostat.
- Configuration for a 4-wire is a Green wire, a White wire, a 24-volt Red wire, and a 24-volt Common wire.
- Connected to terminals G & W & R & C
5 Wire Thermostat System HEAT +FAN or COOL
- If you have heating and air conditioning in your home, then a 5-wire thermostat configuration will be the most typical.
- This configuration includes a 24-volt Red wire for power, a White wire for the heating elements, a Yellow wire for the AC unit, a Green wire for the fan component, and a Common blue or black wire.
- Connected to terminals Y & G & W & R & C
Example: 2-wire Thermostat wiring – millivolt thermostat
- Turn off the power to your HVAC system to ensure safety.
- Remove the old thermostat label and disconnect the wires.
- Bend wires so that they don’t fall into the wall
- Install New thermostat back plate
- Fit batteries to new thermostat and pre-program
- Re-Connect the wires to new thermostat at the same labeled terminals
- Wire colour is not important in 2 wire systems.
- Only W & R or COM & NO terminals are used
- Secure the wires in place and attach the thermostat to the wall plate.
- Turn the power back on and test your new thermostat.