Any smart thermostat options with proper hydronic slab control that don't cost $250+?

[OffGridGuy]

It seems like my choices with proper hydronic slab control (ie: at minimum a slab sensor) that don't cost more than $100 each are either the Honeywell T6 hydronic, the Tekmar 518 or 519, or that ugly Viega one. I'd love to be able to control the air conditioning with some smart thermostats, ideally ZWAVE ones so I can easily control them from Home Assistant and that don't cost $250+ like the WIFI Tekmar ones do. Is anyone aware of anything else that properly supports high mass hydronic?

And yes, I did search this forum for "thermostat" and "smart thermostat" before asking, but if someone has a link to a thread that isn't 3+ years old and out of date I'd love to read that too =)

Thank you.

 

[Bad LP]

High mass doesn’t respond well to larger changes so I limit mine to just a few degrees but don’t feel it’s worth it.
My central AC is off the main T’stat in the LR.
I’ve been using Honeywell stats thru their Redlink modem for years mostly for remote changes. Absolutely flawless and seamless. Easy to change in person.

 

[OffGridGuy]

High mass doesn’t respond well to larger changes so I limit mine to just a few degrees but don’t feel it’s worth it.

The heating side wasn't really the concern beyond something that can properly handle hydronic in concrete slab temperature control. This was more about the cooling side of things where smart control comes into play to let me use a whole house fan and cool outside air instead of several kilowatts of air conditioning. Also, was there a particular model of Honeywell control you used? As far as I can tell only the T6 Pro Hydronic actually seems like it is meant to control hydronic.

 

[Bad LP]

I’m using VisionPRO IAQ stats. A bit older than you 3 years requirement.
I’m also using air temp not slab temps and the ODR is taken care of elsewhere.

I do not have any other connection between RFH or AC. The stat is in H or C mode only. No auto settings.

To be perfectly honest I installed a RFH system in an always cold bathroom from under the subfloor. I was not thrilled with controlling the air temp being controlled by the slab sensor.

 

[sloeffle]

I used the Honeywell T6 ZWave thermostat on my geo system for a week or so. Great thermostat, I liked all of the various setting but something I didn't like is, the thermostat doesn't have deadband / hysteresis that you can set. With a geo furnace you want long run times, since you can't set on that on the T6 my furnace was constantly cycling. I even set it to only run a few times a hour also. The short cycling of the compressor ( big $$$ in a geo ) leads to a much shorter life span according to the HVAC company that installed my geo.

 

[OffGridGuy]

To be perfectly honest I installed a RFH system in an always cold bathroom from under the subfloor. I was not thrilled with controlling the air temp being controlled by the slab sensor.

The Tekmar units have a combined mode for both floor AND air temperature, so as long as the slab stays under the maximum temperature it will increase the heat if the air temp is lower than the set point. And it will always maintain the minimum slab temperature. So it's looking like my only real control option is Tekmar, which is too bad because the WIFI units are all over $200 each.