Easy DIY Guide to Installing a Digital Thermostat

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A simple guide to replacing your old thermostat with a digital model
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If your home has an older thermostat, installing a new digital thermostat is sure to be an upgrade. Old thermostats, especially analog ones, can be inefficient and lead to high heating and cooling bills. Upgrading to a digital thermostat is an inexpensive way to cut your energy costs while making your home more comfortable and cozy. Digital thermostats are actually easy to install—so easy that you won't need an electrician or HVAC technician! This wikiHow article will walk you through the simple steps of installing a new digital thermostat yourself.

This article is based on an interview with our air conditioning specialist, Victor Belavus, owner of 212 HVAC. Check out the full interview here.

Things You Should Know

  • Installing a digital thermostat is usually simple enough to install on your own, even if you're not handy with electronics.
  • Before purchasing a new digital thermostat, make sure it's compatible with your heating and cooling system.
  • Always disconnect the power to your HVAC system before disconnecting or installing a new thermostat.

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Steps

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  1. If you're replacing an older thermostat , you'll need to choose a new digital thermostat that is compatible with your HVAC system. If you have a specific brand or model in mind, such as Google Nest or Honeywell Home, you can search for your model to find out its requirements. If you're heading to the hardware or home improvement store, you'll typically find requirements on each thermostat's packaging.
    • It's a good idea to check the wiring of your current thermostat before buying a new one. To do this, you'll need to turn off the power to your heating and cooling system, remove your thermostat's faceplate, and note the amount and types of wires. You can even take a photo of the wires and bring it to the hardware store so a professional can help you find the right thermostat.
    • Some digital thermostats, especially smart thermostats , require a C-wire. These wires, typically blue and connected to the terminal labeled "C," supply continuous power from your HVAC system. If you're really hoping for a smart thermostat, you'll usually need a C-wire. If you don't have one, opt for a non-smart digital thermostat, or try a C-wire adapter. [1]
  2. Flip the breaker to the heating and cooling system and the wall you're working on. To make sure the heating and cooling system is fully off, try increasing or decreasing the temperature from your existing thermostat to see if it kicks on. If the thermostat activates the furnace or air conditioner, you haven't switched off the correct breaker. [2]
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  3. Lift the cover of the thermostat away from the wall to detach it. Most thermostat covers pop off easily with a little force, though some may be screwed or clasped into the wall plate.
  4. Use a screwdriver to remove the screws, then gently pull the thermostat from the wall. Depending on the thermostat, you may now see visible wires. If not, remove the wall plate covering the wires now. [3]
    • When you remove the thermostat (or the separate wall plate), the wires will remain connected to the base. Don't detach the wires yet.
    • If your thermostat is connected by thick black wires with wire nuts, you have a line voltage system—some newer digital thermostats will not work with these systems.
    • Warning: Use a voltage meter to make sure there is no power extending to the wires. If you don't have one, double-check the fuse box to make sure you've flipped the correct breaker. For good measure, plug something into the wall to make sure it doesn't power on.
  5. If you have multiple colored wires, you'll see that each connects to a terminal that's labeled with a letter. Before disconnecting the wires, write each letter on a small piece of masking tape, then attach it to the corresponding wires. This will help you connect the wires to the proper terminals on the new digital thermostat. [4]
    • You'll usually be able to detach the wires by loosing the screws to which they're connected.
    • If you have a line voltage system with thick black wires, you can detach the wires from the thermostat without labeling them.
    • If you need to attach a C-wire or C-wire adapter, disconnect the fuse to the wall and the fuse for the HVAC system.
  6. Separate your new digital thermostat from its base, then connect the base to the wall. If the screw holes line up, you can use the old ones. If not, drill new holes and use dry wall anchors if needed. Feed the wires through the wall plate so they're easy to access. [5]
    • Use a level when placing the wall plate to ensure that it's even.
  7. Your new digital thermostat also has labeled terminals, though they may be laid out differently. Connect each of the labeled wires to the proper terminal. Check your new thermostat's manual to find the exact steps for your model.
  8. Your thermostat likely came with the batteries it needs to operate, though you'll need to insert them yourself. If the digital thermostat didn't come with batteries, check the manual to learn which type of batteries (and how many) it requires.
  9. Position the thermostat face over the wall plate so it lines up, then snap it into place. If the face requires screws or clips, use the included screws or clips to secure it.
  10. Once the thermostat is installed, you can return to your breaker box and restore the power you previously disconnected.
  11. The steps to set up and operate your new digital thermostat vary by model, so check the manual for specific instructions.
    • If your digital thermostat is the programmable kind , program in the desired temperature or temperature range. The thermostat will regulate the temperature in your home to this degree and keep it there.
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Community Q&A

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  • Question
    What do I do if there is no blue wire?
    Community Answer
    If you are talking about the wire for the C (common) terminal you will either need to buy a thermostat that does not require a C terminal or you will have to buy a 24 volt transformer and wire that to an electrical box.
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  • Question
    How do I change the battery of a digital thermostat?
    Community Answer
    You will need to remove the front cover or remove the thermostat from the wall to access the battery.
    Thanks! We're glad this was helpful.
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  • Question
    I replaced the thermostat. The heat is working, but not the air. What do I do if the air does not come on?
    Community Answer
    Verify you connected the wires in the manner appropriate for your air conditioner. The thermostat should have come with instructions.
    Thanks! We're glad this was helpful.
    Thank you for your feedback.
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      Tips

      • Set the temperature one degree lower in winter when you aren't at home and when you are sleeping, and one degree higher during these times in the summer months. Your new digital thermostat will accurately hold these settings and help you save money on your energy bills each season.
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      • In most cases, it is pretty simple to install a digital thermostat.
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      • Don't hesitate to ask a home improvement or hardware store employee if you have questions about selecting a digital thermostat.
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      Warnings

      • Follow digital thermostat installation instructions closely to avoid injury or problems.
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      • Never attempt to install a digital thermostat until the power to your furnace is turned off. Doing so could result in shock or electrocution.
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      • Never mix up the wires when installing a digital thermostat. If your old system is a very complicated one and the wires are confusing, you might want to consult a professional for help.
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      Things You'll Need

      • Digital thermostat
      • Screwdriver
      • Masking tape
      • Dry wall mounts
      • Drill

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      Expert Interview

      Thanks for reading our article! If you’d like to learn more about heating and cooling, check out our in-depth interview with Victor Belavus .

      References

      1. ↑ https://www.honeywellhome.com/us/en/support/everything-you-need-to-know-about-a-c-wire/
      2. ↑ https://www.youtube.com/watch?v=zBIrPxQrRTQ
      3. ↑ https://www.youtube.com/watch?v=epxXy6X2AHU
      4. ↑ https://www.bhg.com/home-improvement/electrical/how-to-replace-a-thermostat-for-baseboard-heaters/
      5. ↑ https://www.youtube.com/watch?v=epxXy6X2AHU

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