Wiring a Furnace Thermostat

A man works on a thermostat
  • 1-3 hours
  • Intermediate
  • 0-50
What You'll Need
An 18 gauge 2 wire, thermostat wire
Wire strippers
Wire staples
Wire cutters
Plastic drywall anchors
Small screwdriver

Thermostat wiring is a relatively easy job that almost every homeowner can manage. A heating system with a simple setup includes a furnace thermostat wire that has two internal wires. Such a wiring system works only for heating a space. Follow these simple steps if you want to wire a thermostat to your furnace.

Step 1 - Get the Furnace Ready

Begin your project by turning off power to the furnace. The power switch is usually located on the side of the furnace. Run the connected thermostat wire from the furnace to the place where the thermostat will be located. Remember that the wire has to go through the furnace covering into the control panel. You will have to make an opening if there isn’t one. Ensure that the opening has a rubber sleeve to prevent the wire from getting cut.

Step 2 - Mount the Thermostat

Once you know the mounting location of the thermostat, make a marking there. Drill a hole in the drywall. Feed the wire from the furnace through the hole in the wall with fish tape. Fix the thermostat’s wall plate on the wall. The best way to fasten the wall plate is by using drywall anchors at the selected location.

Step 3 - Make the Connections

A two-wire thermostat wire has one white and one red wire. These are encased in a brown insulating coating. Strip back both the white and red wires about ¼ of an inch at both ends. Connect the white wire to the terminal that says “W” on the thermostat and furnace. Similarly, connect the red wire to the thermostat and furnace “R” terminal. Snap back the thermostat to the wall plate.

Step 4 - Check the Furnace Thermostat

When you are sure that all wiring has been done correctly, you can check the thermostat to see if it is working properly. To do this, switch on the power to the furnace. Set the thermostat on “heat” mode and program it to the preferred setting. If the room temperature is lower than the setting on the thermostat, the furnace cycle will start. This cycle will begin to heat that particular space.

You can also use a programmable thermostat if you want to save costs. A programmable thermostat can automatically reduce the temperature when you are not at home or are asleep.

Wiring a furnace thermostat can be done with basic home improvement skills. You should follow all the safety procedures while wiring the thermostat. Avoid working around live wires. Remember to cut the power to the furnace. Failing to do this before wiring the thermostat can damage to the furnace.