How to Replace a Thermostat

Improve your home’s energy efficiency and save money with a programmable or smart thermostat. Today’s thermostat technology is leading the way for energy efficiency and can save you money.

Remember these three words. Remove. Replace and Recycle. Safely dispose of older mercury-containing thermostats. It’s the law. If you remove a thermostat that contains mercury, you are required to properly dispose of the unit.

Follow these steps to replace your old thermostat…

  1. Turn the thermostat to the off position.

  2. Shut off the power to your HVAC system.
    Shut off the power to your heating and/or air conditioning system at the circuit breaker box, fuse box, or switch at the furnace, air handler.

  3. Thermostat Wiring Connections.
    Remove the existing thermostat, but leave the wall plate in place for now so you can note how the wires are connected. Test the wires with a circuit tester to verify the power is off. Note: Some thermostats only have one side of the circuit, so a circuit tester may not work. It is best to shut off the power at the source. Watch our related DIY Basics videos:

  4. Label Thermostat Wiring.
    Label each wire on your existing system with the letter designation of the terminal it’s connected to. Ignore the wire color—use only letters to identify the wires. Your new thermostat may come with pre-printed labels for this step.

  5. Take a Picture of the Thermostat Wiring.
    Take a picture of the existing connections so you’ll have a visual reference later if you need it.

  6. Remove the Old Thermostat.
    Disconnect the wires and remove the existing wall plate. Not all thermostats have wall plates. Caution: Older thermostats with glass tubes contain mercury. Use caution when handling and check with your local recycling company for disposal instructions.

  7. Remove Wall Anchors.
    Depending on the shape and size of your new thermostat, you may need to remove the old wall anchors and patch the holes.

  8. Recycle.
    Be sure to carefully and properly dispose of a mercury containing thermostat. Click here to find a location near you. It’s the law.

Thermostat Recycling Corporation (TRC) does not specifically endorse or recommend Do-It-Yourself (DIY) projects. All DIY projects are purely “at your own risk”. As with any DIY project, unfamiliarity with the tools and process can be dangerous. This post and the information contained herein should be considered as a theoretical guide. If you are at all uncomfortable or inexperienced working on these projects (especially but not limited to electronics and mechanical), please reconsider doing the job yourself. It is very possible on any DIY project to damage your home or property, void your property insurance, create a hazardous condition, or harm or even kill yourself or others. TRC will not be held responsible for any injury due to the misuse or misunderstanding of any DIY project. By using this website, you agree to indemnify Thermostat Recycling Corporation (“The Company”), its officers, directors, employees, agents, distributors, affiliates, subsidiaries and their related companies for any and all claims, damages, losses and causes of action arising out of your breach or alleged breach of this agreement. The information on this site are distributed “as is” and appear on the site without express or implied warranties of any kind, except those required by the relevant legislation. In particular the Company makes no warranty as to the accuracy, quality, completeness or applicability of the information provided. The information on this website is for informational and promotional purposes. You may not rely on any information and opinions expressed in it for any other purpose. Neither the Company, nor its officers, directors, employees, agents, distributors, affiliates, subsidiaries and their related companies are responsible or liable for any loss damage (including, but not limited to, actual, consequential, or punitive), liability, claim, or any other injury or cause related to or resulting from any information posted on the Company’s website.

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