ST compatible thermostats for "communicating"/ClimateTalk HVAC systems

I’m trying to find a WiFi/app enabled thermostat that is compatible with both SmartThings and my HVAC. A few years ago when I had to replace my AC, they put in a fancy ComfortNet thermostat which communicates to the HVAC motherboard using 4 wires (instead of 5), one of which uses a “ClimateTalk” serial communication protocol. As a result, the Ecobee3, Nest, Lyric, etc are not compatible with my system. What thermostats can I use that will work with my HVAC and ST? I’ve spent hours researching, but can’t seem to find the right combination.



Unfortunately, you’ll have to get with you local AC dealer and ask if your specific unit has a “conventional thermostat interface” module available for it. This will allow you to use any ST compatible stat. You may still need to add a “neutral” conductor if you don’t have enough wires between the AC unit and the stat.


Thanks. I’ll check into that.


I also have this type of system but I am not willing to move away from my ComfortNet thermostats (I have 3 in a zoned system along with a UT-3000 from EWC). You absolutely can move to a non-communicating thermostat as long as you’re willing to give up some of the features it offers (more fan controll, external temp reporting, thermostat humidifier control and better modulating furnace control if you have those things, etc… ) as a standard thermostat can generally only operate in off/on for fan and Heat/Cool 1-2 stage (including heatpump, if you have that).

With my current setup, each floor can call individually for humidity in the winter when it’s needed and each floor can instruct the HVAC to run in dehumidify mode in the summer when it’s too humid inside (you can also install a dehumidifier, but my system just runs the AC slightly differently to help dehumidify).

Sadly, I’m stuck using Honeywell’s ‘My Total Comfort Connect’ system for controlling everything which does not easily integrate into smartthings! It looks like there are a few attempts at solutions to integrate the two but nothing official on either side–Honeywell needs to permit API access or something but doesn’t appear too concerned with providing anything like this. At this point, we are relegated to using two different systems–MyTotalComfortConnect and Smart Things-- separately to automate our homes and it’s really not cool. I was hopeful when I had my system installed 2 years ago that more thermostats would be designed for ClimateTalk/ComfortNet or, at least, the current options would be built upon but this doesn’t seem to be happening. It’s very frustrating. I’ve contacted Honeywell a few times about it and they don’t seem concerned. They are supposed to have some sort of program around it. Maybe someone will design an IFTTT type of interface?