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If you recently purchased a Honeywell wifi thermostat and it says that you need a c-wire, don’t panic! These instructions will guide you through the process of installing one without one.

There are a few tutorials online that give step-by-step instructions for how to connect your thermostat wirelessly, but these were found to be more cumbersome than they needed to be.

This article will go through the steps quickly, as we believe that most people won’t need more than this

Note: this process has only been tested in the USA. If you are outside of the US, please check to make sure that your thermostat will work in your area before starting.

If you haven’t purchased your smart thermostat yet, you might want to read about the use of the C wire and why you might not need one. We’ve written an article on this topic, which also includes reviews on the best smart thermostats that do not require a C wire.

1. Getting the Right Supplies

For this project, you will need the following tools:
Cordless drill
1/8 inch drill bit
Various size Phillips head screwdrivers
Scissors or a utility knife
Level or ruler (optional)

Using Rechargeable Batteries
If your thermostat came with rechargeable batteries, let them charge first. You can use these batteries later as they will be better than non-rechargeable batteries. You can check if the batteries are full enough this by putting them into the thermostat. If the low power supply lights unit flash, then you need new batteries or need to charge your batteries some more.

2. Remove the Old Thermostat

The first step is to remove the old thermostat. This is a fairly easy process.(1) Remove the screws holding the back cover to the unit, and then (2) gently pry it away from the unit. (3) Once the old unit is removed, gently pull the wires out and should now be exposed.

3. Modifying the Wiring

You should remove all of the old wires and cut off any that you do not need: (1) Cut any non-essential wires, (2) Remove any additional power supply wires that you don’t need. If you have a multi-zone thermostat (dual zone), then you will also have wiring for each zone in a different location. All of these can be removed as well.

4. Testing for C Wire Requirement of the Thermostat

To determine if you need a C-wire by testing to see if your thermostat can run on batteries for at least one day. If your thermostat can run on batteries for an entire day, you will be able to use the thermostat with batteries. The reason that this is the case is because if a smart thermostat’s batteries are only designed to sustain it during power outages, it’s features will take up too much power and they will quickly run out.

5. Connecting The Power Line Wire of the Honeywell Wifi Thermostat

  1. Find the left and right terminals on your electricity source. These are usually labeled L1 or L2 and N or N/L (for neutral) and may be color-coded as well (brown for ground)
  2. If required, use the utility knife to strip back about an inch of insulation on each of the power line wires.
    3.Connect the positive wire from your power source to that terminal using a screwdriver or a wire stripper; make sure it’s tight. Then connect the negative wire.
  3. At this point, you should have the only 2 wires required connected.

Note: If you are not certain which wire is which you can simply connect them one way. If the thermostat cannot switch the power on and off then you’ll have to connect the wires the other way around.

6. Testing the Thermostat After the Installation

The thermostat is now installed, but before you put the cover panel back on you should test to make sure everything is working. Here’s how:

  1. With all wires connected, go ahead and turn on the device and see if it switches on.
  2. If you’re not sure if your thermostat is actually turning on the power to the heating or cooling system, then turn it up, while listening for the heating/cooling appliance to turn on. If it’s not working properly, wait for an hour or so and try again.

What to do if the Smart Thermostat Doesn’t Work
If after waiting an hour and testing again the smart thermostat doesn’t work, return to step D to change the position of the two power line wires.

You should also find your thermostat model and review whether your problem has been experienced by others before. This could be a simple fix that you can save you a lot of time.
You can do this by looking at the back of your thermostat and look for a model number. If you cannot find the number use the video below for more detailed instructions.

Finally, we suggest to reach out to Honeywell’s customer service representatives, which can be contacted on this page:

Final Thoughts

Congratulations! You just successfully installed your new thermostat without requiring a C wire. We hope you found this article helpful and that it saved you some time.

If you’re looking to get the most out of your smart thermostat, please check out our article on the best smart home devices, which you can use in combination with your smart thermostat.

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