Replacing Honeywell THX9421R5021WW with a Nest learning thermostat

[Aoshal]

 

 

Hello,

I am trying to replace my Honeywell THX9421R5021WW with a Nest learning thermostat. My old unit controls gas furnace (heat) forced air AC and humidifier. I only have two wires connected to the Honeywell thermostat (R and C). How do I connect the nest.

I appreciate any help I can get.

 

[EdwardT]

Hi Aoshal,

Thanks for reaching out. Based on the wiring, it looks like your system is proprietary. Proprietary systems aren’t compatible with Google Nest thermostats. However, some proprietary systems can be rewired by a pro installer to be compatible. You can click on this link to learn more about our Nest Pro services.

Thanks,

Edward

[Aoshal]

Thanks Edward, I figured as much yesterday when I noticed a Honeywell thermostat module connected to the air handler. Apparently, Honeywell uses it’s own protocol and clearly the wiring is not compatible with any other thermostat.

going to hire a pro. Thanks again

[EdwardT]

Hi Aoshal,

Thanks for the update. Let us know the results once your Nest Thermostat is installed. Keep us posted.

Thanks,

Edward

[Jhonleanmel]

Hi folks,

Chiming in to see if you still need assistance with this. Let us know if you have additional questions ― we'd love to help.

Best,
Mel

[Jhonleanmel]

Hi everyone,

Just one quick final check in here since activity has slowed down. We'll be locking the thread in the next 24 hours, but if you still need help, I would be happy to keep it open. If there's more we can do, just let me know.

Thanks,
Mel