In general, you do not need to turn off the furnace to change the thermostat. The furnace and thermostat operate independently of each other, and changing the thermostat settings should not require shutting off the furnace.
However, it is essential to ensure safety when working with electrical components. Here are some general guidelines to follow when changing the thermostat:
Turn Off Power to the Thermostat: Before changing the thermostat, you should turn off the power to the thermostat itself. This can usually be done by switching off the circuit breaker or removing the fuse that supplies power to the thermostat. This step ensures you don't accidentally encounter live wires while working on the thermostat.
Follow the Thermostat's Installation Instructions: Each thermostat model may have specific installation instructions provided by the manufacturer. It's important to refer to these instructions to properly install and wire the new thermostat. The instructions will guide you through the process and any necessary precautions.
Take Note of Wiring and Labeling: Before disconnecting the wires from the existing thermostat, take a picture or make note of how the wires are connected. Additionally, some thermostats have labeled terminals indicating where each wire should be connected. This information will be helpful when wiring the new thermostat.
Connect the New Thermostat: Once the old thermostat is disconnected, you can proceed to wire the new thermostat following the manufacturer's instructions. Ensure that each wire is connected to the corresponding terminal on the new thermostat.
Restore Power: After the new thermostat is installed and wired correctly, you can restore power to the thermostat by turning on the circuit breaker or reinserting the fuse. The furnace should resume normal operation, and you can then set the desired temperature on the new thermostat.
It's worth noting that if you are uncomfortable or uncertain about working with electrical components, it is advisable to seek the assistance of a professional HVAC technician. They have the necessary expertise to handle the installation and wiring safely.