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How to Install a Home Furnace Thermostat


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Remove the Old Thermostat

Removing the Old Thermostat
First you must disconnect and remove the old thermostat, being mindful as to the number and colors of the wires.
  • Shut off power to the furnace. You will find a circuit breaker or fuse that controls the furnace in the electrical service panel or fuse box. Find it and turn the circuit off by turning the circuit breaker to the "off" position or unscrewing the fuse.
  • Remove the old thermostat and expose the old wires.
  • It is a good idea to take a digital picture of the wires as they were connected to the original thermostat.
  • Disconnect the wires but be careful not to let them fall into the wall!
  • If they are not colored, label them as to which terminal they were connected.
  • Remove the old thermostat mounting plate from the wall.

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