I have a Kronos GA11 thermostat (it says it is compliant with OpenTherm™ v3.0 Smart Power Mode – Medium Power.). Is OT Thing compliant with OpenTherm™ v3.0 Smart Power Mode – Medium Power, and thus may I use the Kronos GA11 thermostat in slave mode with OT Thing ?
Hi, Open Therm Smart Power is working when I connect my OT Thing with my Honeywell Room unit, your Kronos should work too.
Regards
Stefan
Hi! Seems your boiler does not provide the temperature above 20°. You can have a look to the log page of the ot thing and search for the outside temp frames to see what your boiler provides for real.
Regards
Stefan
Hi,
the OT Thing webinterface shows the outside temp (boiler) above 20° but HA did it just up to 20 (this was in FW v2.2).
Now I have FW 2.3 up and running and can see the 1-Wire sensor (DS18B20) in HA but I lost the outside temp (boiler) completely in HA, do you have any Infos abt that?
The outside temperature control in HA is for setting the outside temperature via MQTT when your boiler does not have that sensor. If your outside temperature source in OT Thing is NOT configured to MQTT this control will disappear in HA.
But I added autodiscovery to the value reported from the boiler, see firmware v2.4.
You can connect multiple sensors in parallel. From firmware side it works:
Maybe there is an error on your wiring.
Hello,
Are you able to ship to the UK?
I saw the cost for the shipping was more than the product and now the option is not available any longer.
Thanks
Phil
Maybe, I will try it again…
Firmware 2.5 is out now:
- supports overriding some values in repeater mode. A room unit can be used to set the desired room set temperature and the OT thing can calculate the flow temperature and override the flow temperature of the room unit.
- minor bugfixes
- add some additional values (number of flame signal low, number of unsuccessful starts, DHW operating hour…)
I received my OT Thing via ShipGerman, thanks for the suggestion.
Having my first look at it now, I have noticed the following with version 2.5 firmware that the MQTT sensors when viewed in HA are a mix of German and English.
I can see here that you have updated the values on your Github, I have not searched in your code to see where this is then used.
Thanks for making a great device, I am looking forward to learning what it can do and getting it setup in HA.
I release firmware v2.6. Translations should be fixed.
Hi Stefan,
I’m looking for a solution to a problem and I hope your device might be the answer.
I’m using the Drayton Wiser Kit 1 system, which communicates via OpenTherm with my Baxi 600 combi boiler. The issue is that Wiser doesn’t control the Domestic Hot Water (DHW) temperature, but the boiler expects that data when OpenTherm is connected. Since it doesn’t receive a DHW setpoint, it defaults to 60°C.
At the moment, I’m not looking to control the heating temperatures — I’d just like to relay the OpenTherm messages from Wiser to the boiler, but inject a fixed DHW temperature (e.g., 45°C).
Would OT Thing allow me to do that? Is it as simple as connecting the OpenTherm wires from the boiler to OT Thing, and then from OT Thing to Wiser, and configuring Home Assistant to send the missing DHW data?
If so, that would be fantastic! Also, do you offer shipping to the UK, or would I need to go through family in the EU?
Thanks in advance!
Hi Aron,
this is a tough one. In repeater mode the OT Thing is not able to send messages to the boiler as this would mean to heave 2 masters which would cause collisions. It could work if you set the OT Thing to master mode, then, I could build an option to heave the OT Things’s slave interface enabled, and “adopt” the flow set temperature sent from the room unit.
For shipping to UK you could use shipgerman.com.
Stefan
Hi Stefan,
Thanks for the quick reply!
To be honest, I didn’t fully follow the technical part 
I had the impression that with some OpenTherm gateways, you can place them physically between the boiler and the existing controller — they’d intercept the signal, inject something like a fixed DHW temperature, and then pass the rest through unchanged. Your OT Thing came up as one of the possible devices for that.
From what you’re saying, it sounds like that kind of “inline modification” isn’t currently possible in repeater mode, because it would mean having two OpenTherm masters on the same bus — which would cause conflicts. Is that what you meant by “2 masters”?
If so, I guess I’m back to square one. But I’m curious: if OT Thing were in master mode and could “adopt” the flow setpoint from the Wiser, would that mean it could also inject the DHW temperature and still pass along the heating setpoint? Or would that break the Wiser’s control entirely?
Appreciate your time - and thanks for the tip about shipgerman.com
The sticking point is the part you call “intercept”. In repeater/gateway mode, messages from the room unit are forwarded to the boiler and those message can be also modified. But when the room unit does not sent a DHW message at all it can not be modified.
In master mode all communcation to the boiler is initiated by the OT Thing, but the slaveinterface (to which the room unit is connected to) could additionally be activated so that OT Thing answeres the requests from the room unit on it’s own. In this way, the OT Thing could “pick up” some values from the room unit and use those for it’s master side to the boiler. A bit tricky though, but I hope it gets clearer.