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Oct 15, 2016

Connecting the K Wire on the Nest Thermostat

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Connecting the K Wire on the Nest Thermostat

In this short blog entry I will explain where to insert the K Wire on the Nest Thermostat.

First off what is the Nest Thermostat for those who are unaware – Nest Labs is a home automation producer of programmable, self-learning, sensor-driven, Wi-Fi-enabled thermostats, smoke detectors, and other security systems. It introduced the Nest Learning Thermostat in 2011 as its first product. – Wikipedia on Nest Labs

So here we go a few weeks ago I purchased a Nest Thermostat for the family, however I ran into an issue on where to connect the K Wire that was labeled on my Honeywell Digital Thermostat.

K Wire Nest Thermostat

After much troubleshooting and following the guide via the Nest Thermostat Manual for more information I decided to call Nest regarding this. They asked me to email them over a picture of above to them and after doing so they kindly said that my Nest Thermostat would not be compatible with my home and they deeply apologized.

Nest Thermostat Wiring

I mentioned to Nicole that I was pretty sure that the K Wire needed to be inserted into the Y1 or Y2 slot of the Nest Thermostat and for validation I decided to do a YouTube Search regarding this. Great success, I was able to find this really simple video (no illustrations) that stated that all you needed to do is to insert the K Wire from into the Y1 slot of the Nest Thermostat. Check out the video below.

Nest Thermostat Wire Connections

Where to Connect the K wire on your Nest thermostat?

So after doing this the Nest Thermostat has been installed and everything has been working flawlessly!


  • scottula

    I have the same wiring setup with a Honeywell thermostat currently. I was reading that if you connect the K wire to the Y1 connector, you lose manual fan control. Are you able to turn the fan on by itself without turning on the heating or cooling?

    Thanks for info!

    2017-04-27 - 8:33 pm Reply
  • David Polanco

    Hey, yep. I am able to power the Nest with the fan. Originally I was only given the heat option w/ fan but then after making the changes as explained above I was able to get it working. Let me know how it goes for you or if you need help I will be happy to upload a video or take a picture of what I have here if you need it.

    2017-04-27 - 9:16 pm Reply

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