4 Steps to Change an Oil Furnace Thermostat

A man adjusts a furnace.
  • 2-4 hours
  • Advanced
  • 200-500
What You'll Need
New thermostat
Masking tape

Changing the thermostat that controls the operation of your oil furnace is an easy way to update your heating system. Replacing a thermostat, particularly an old dial-type thermostat is a small expense with a long term payoff. Most modern thermostats have numerous features that enable you to save money on your utility bills, but the most important is perhaps the fact that you can program the thermostat to a specific temperature to accommodate the lifestyle of those in your household.

You can maintain a lower temperature during the day, when everyone is gone, and program the thermostat to turn up the heat (or turn on the air conditioning) a little while before everyone comes home. Installing a new thermostat may be a little daunting for a lot of people, but it is a relatively easy do-it-yourself project that can be completed in a short amount of time.

Step 1 - Remove the Old Thermostat

Start by tripping the breaker that supplies power to the thermostat. While there is not a lot of electricity running to it, it is better to be safe. Remove the faceplate to the existing thermostat. You shouldn't unscrew the existing thermostat just yet. You will need to first disconnect the wires. Depending on the style of the existing thermostat, you may have to remove it to get at the wires.

Step 2 - Disconnect Wiring

Disconnect each wire running to the thermostat, one at a time. Using the masking tape and pen, mark each wire with the corresponding letter on the thermostat where the wire is connected. Place a pencil close to the wall and wrap each wire around the pencil after you have disconnected them and will prevent them from slipping back, into the wall where they will need to be fished out.

Step 3 - Reconnect Wiring

Each thermostat will be a little different when reconnecting the existing wiring. Read the directions thoroughly for the particular thermostat that you have chosen. There should be several wiring configurations in the instructions, of which at least one should accommodate your existing wiring pattern. Once you have identified the correct wiring configuration, reconnect the wires to the new thermostat appropriately.

Step 4 - Install Thermostat

You will need to reattach the new thermostat to the wall, usually using screws. Typically, using anchors is unnecessary, as the thermostat is not very heavy. Again, follow the directions that came with the thermostat when securing it to the wall. Generally, this will just entail using the screwdriver to drive a couple of screws through the provided holes in the thermostat and into the drywall behind it. Install any batteries that are needed. Program the thermostat for the temperatures desired on particular days and times. Finally, turn the electricity back on. Test the operation of the new thermostat by adjusting the settings and monitoring the furnace or air conditioner to ensure that they come on or turn off appropriately.