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How Do I Replace a Thermostat?

John Turpin is our resident home service repair expert here at Service Direct. He’s got the knowledge and experience to help homeowners like you make sense of most home repair issues. And with Service Direct, we connect you with top-tier service professionals to help with any repairs needed.

Learn How to Install a Thermostat for Central Heating

Replacing a thermostat is a common home improvement task that can help improve energy efficiency and enhance the comfort of your home. If you want to upgrade to a programmable thermostat, replacing it is a relatively straightforward process.

We’re here to help you do this, guiding you through the steps on how to install a thermostat for central heating of your home. Replacing a thermostat can be intimidating at first glance, but rest assured a DIY approach is entirely possible. Read on to find out how to replace a thermostat, from gathering the necessary tools to completing the installation.

Thermostat And Efficiency Upgrade
Updating or replacing the thermostat can reduce your household energy consumption.

How to Change a Thermostat: A Step-by-Step Guide

You’ve been asking yourself, “How do I replace a thermostat?” Well, you’re on the right page. Follow the steps below to change your old, faulty thermostat on your own.

1. Gather the Tools and Materials

  • New Thermostat – Choose a thermostat compatible with your heating and cooling system. Consider features like programmability, Wi-Fi connectivity, and energy-saving options based on your preferences.
  • Screwdriver – Depending on the type of screws used, you may need a Phillips or flat-head screwdriver.
  • Voltage Tester – This tool helps ensure the power to your thermostat is turned off before you begin working.
  • Wire labels – Use these to label the wires connected to your existing thermostat for easy identification during installation.
  • Pen and Paper – Take notes or draw a diagram of the existing wiring connections for reference.

2. Turn Off the Power to the Thermostat

Turn off the power supply to the thermostat to ensure safety during the replacement process. Locate the circuit breaker or fuse controlling the thermostat’s electrical connection and switch it off. For added safety, use a voltage tester to verify that the power is indeed off before proceeding.

3. Remove the Old Thermostat

Carefully remove the cover of the old thermostat to expose the wiring. Usually, thermostats are held in place by screws, so use the appropriate screwdriver to remove them. Once the screws are removed, gently pull the thermostat away from the wall. This should reveal the wiring connections behind the device.

4. Label the Wiring

Using wire labels or pen and paper, label the wires connected to the existing thermostat. The standard labels are R (red), W (white), Y (yellow), G (green), and C (blue or black). Keep in mind, however, that this labeling may vary depending on your specific system. Take note of the corresponding terminals to which each wire is connected.

5. Disconnect the Wires

Loosen the terminal screws to release the wires from the existing thermostat. Take care not to let the wires fall back into the wall. If needed, use tape to secure the wires and prevent them from slipping away.

Our resident home repair guru, John Turpin, outlines his step-by-step guide on changing a thermostat, including some clever tips and tricks of the trade.

6. Remove the Old Mounting Plate

After disconnecting the wires, remove the old mounting plate from the wall. Inspect the wall for any damage or excessive debris. Clean the area, if necessary, to ensure a smooth installation of the new thermostat.

7. Install the New Mounting Plate

Take the new mounting plate provided with your thermostat and align it with the existing holes, or mark new holes if required. Use screws appropriate for your wall type (drywall, plaster, etc.) to secure the mounting plate in place.

8. Connect the New Wiring

Refer to the labels or notes you made earlier and connect the corresponding wires to the appropriate terminals on the new thermostat. Follow the manufacturer’s instructions for specific wiring guidelines, as some thermostats may have additional terminals or different color coding.

9. Attach the New Thermostat

Now is the time to actually replace the thermostat. Carefully position the new thermostat onto the mounting plate, aligning it with the screw holes. Insert and tighten the screws to secure the thermostat in place.

10. Restore Power

Once the new thermostat is securely installed, restore power to the thermostat by turning on the circuit breaker or fuse. The thermostat should power up, and you can follow the manufacturer’s instructions to set up and program your new thermostat.

11. Test Heating and Cooling Systems

Ensure that it is functioning correctly by testing both the heating and cooling systems. Set it to the desired temperature for each mode and verify that the heating and cooling system turns on and off as expected.

Replacing a thermostat is a task that many homeowners can tackle themselves with little guidance. By following the step-by-step guide, you can confidently replace your old thermostat with a new one and enjoy its benefits.

Correctly Wiring Thermostat
Follow DIY steps closely to ensure your thermostat is correctly connected and fully functional.

Replacing a Thermostat – DIY vs. Pro

Are you wondering who to call to replace your thermostat? Well, you have two options for this dilemma – do it yourself (DIY) or hire a professional. Each one has pros and cons, which we will consider below:


  1. Cost Savings – Doing it yourself can be more cost-effective since you won’t have to pay for professional labor.
  2. Learning Opportunity – Replacing a thermostat can be a relatively simple task, and doing it yourself allows you to gain knowledge and experience.
  3. Convenience – You can do it on your own time and schedule without having to wait for a professional.

However, there are a few things to consider before attempting a DIY thermostat replacement:

  1. Skill and Knowledge – Make sure you have a basic understanding of electrical systems and thermostat installation. Read the manufacturer’s instructions and any relevant guides thoroughly.
  2. Safety – Working with electrical components can be dangerous if not done correctly. Ensure you turn off the power at the breaker before starting the installation.
  3. Compatibility – Ensure that the new thermostat is compatible with your heating and cooling system. Different systems may require specific thermostats.

Professional Installation:

  1. Expertise – HVAC professionals have the knowledge and experience to handle thermostat replacements efficiently and accurately.
  2. Warranty and Guarantees – Hiring a professional may come with warranties or guarantees on their workmanship and the thermostat itself.
  3. Complex Systems – If you have a complex heating and cooling system, such as a zoned system or one with multiple stages, a professional can ensure proper installation and setup.

But before you hire a professional to replace your thermostat, there are some factors to consider:

  1. Time and Convenience – If you lack the time or confidence to do the installation yourself, hiring a professional can save you a world of hassle.
  2. Safety and Peace of Mind – Professionals are trained to handle electrical systems safely, reducing the risk of accidents or damage.
  3. System Optimization – HVAC professionals can optimize your system for efficiency and performance during the installation.

Ultimately, the decision depends on your comfort level with DIY projects, the complexity of your system, and your budget. If you’re unsure about any aspect of the installation or have a complex system, it’s generally advisable to hire a professional to replace a thermostat.

HVAC Thermostat Installation And Replacement
Some thermostats require an upgrade inside the HVAC unit to match the wall unit.

Thermostat Replacement FAQs

Do I need an electrician to replace a thermostat?

In most cases, replacing a thermostat doesn’t require the assistance of an electrician. However, it’s important to note that thermostat installations involve working with electrical components. As such, it’s essential to follow safety precautions and have a basic understanding of electrical systems.

Can I replace my thermostat myself?

Yes, it is possible to replace a thermostat yourself if you’re comfortable working with electrical components and have a basic understanding of wiring. Replacing a thermostat typically involves low-voltage wiring, which is considered safe for homeowners to handle.

Can I replace an old thermostat with a smart thermostat?

In most cases, you can replace an old thermostat with a smart thermostat but it depends on your specific heating and cooling system. Make sure to choose a smart thermostat compatible with your system and follow the manufacturer’s instructions for installation.

Do I need to reprogram a new thermostat?

Yes. After replacing a thermostat, you will typically need to program it with your desired temperature settings. Follow the manufacturer’s instructions for programming and setting up your new thermostat.

Hire a Local HVAC Pro

Remember to exercise caution when trying to replace your thermostat and if you encounter any difficulties, consult a professional HVAC technician for assistance. You can reach one of local experts easily using the phone number or form on this page.

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