Looking for a 24V thermostat: Zigbee, NO cloud and external probe

I'm looking for a zigbee thermostat able to control an "old* (10 years) geothermal unit (Geoconfort), hooked to a ventilation system (no hydronics), able to run without cloud and with an external temperature probe.

The geo unit itself command does not have any special needs: it works with most 24V thermostat (Honeywell, White-Rodgers, Venstar). Usual full wiring is provided (fan, compressor, changeover valve, heat, power, common, alarm: 7 wires in total, not all obligatory used or needed).

Normally, geothermal controls are very simple: you don't change often temperature. Because of the way it works (you don't heat, you extract heat from the soil. You don't cool, you inject heat in the soil), it's useless to change temperature based on occupancy.

Mainly, in my home: 21C from september to april (heating mode), 21C from april to july (no heat, no cooling), 21C from july to september (cooling). So, I just switch from heating to cooling in july... and cooling to heating in september. No additional furnace or heaters in the house.

Specific features:

  • NO cloud. Must be fully functionnal without internet

  • external probe. because a HE tablet will replace the thermostat, it will be moved elsewhere, so the external probe needed to measure the temperature in the corridor. I know I can average the temperature of my temperature sensors disposed everywhere, but I need a local way to measure the main temperature in case of problems (power outage, dead hub, etc)

  • able to blow regularly air, on timed schedule. This is NOT mandatory because HE can do that task if the thermostat is controlled

  • NOT Mandatory but could be plus: Controls humidification & dehumidification

  • of course, HE compatible (standard or custom driver/app)

I have a Venstar T5800 for now (without external probe), with API. tested with an app found here. not functionning, except if I switch (on the HE device itself) between auto and manual fan... Nothing else.

Contacted the programmer: no news. I could be able to build an app but I need to know how to create a functionnal one from scratch. Never did such kind of programming.

Venstar API ?

I want to enhance the connection between my thermostat and my house. But will gladly swap to a new thermostat if I find one.

Thank you

Qubino ZMNHID3 perhaps?

Other choices will require you to add the external probe separately.

Centralite Pearl
Sinope TH1400ZB
Zen Thermostat

All of these are on the compatible devices list

Have a look at the Sinope TH1300ZB, it has an external temp probe.

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Isn't that Mains voltage only? He's looking for 24v so I suggested the Sinope TH1400ZB , but does that also have an external probe?

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dohhh, yeah you are correct.
The TH1400ZB does support this add on external probe:


Unfortunately, this Sinope thermostats (both models) are not working with fan systems like my geothermal unit, even they are working with hydronic floor heating.
I'll check the others...
Thank you anyway for your replies

*Edit: unfortunately, all those nice thermostat have no external temperature sensors :disappointed_relieved:
Will probably learn how to write a drive for my Venstar...