Im returning our existing radiator valves (Tado X) as I want something I can run directly in Home Assistant using Zigbee without any cloud, crippled features, subscriptions etc.
In our livingroom, we have 4 radiators (with Tado X TRVs) and 1 wireless temperature sensor that regulates the 4 radiators individually so they end up giving the room the target temp I want. I’ve noticed that all 4 radiators are adjusted individually by Tado’s algorithm.
How do I do the same in Home Assistant with, say, Sonoff or Aqara TRVs and a temperature sensor?
If you only have one temperature sensor, as a logical matter your view of the temperature in the room, a three-dimensional space, is limited to one one-dimensional speck: the (X, Y, Z) coordinate of the temperature sensor’s location.
Without more information, I am at a loss to suggest an algorithm that will be more effective than starting and stopping all of the heaters in unison–because on what basis are you going to distinguish the heaters?
I don’t know what Tado’s (presumably proprietary) algorithm does, or what additional information it might have (like distance to the temperature sensor from each individual heater).
I’m sure you, too, could design an algorithm that uses more information than just the one temperature sensor: shape of the room, whether or not windows are open, which heater is located in a draughty part of the room, etc. But since only you really know what you expect from this solution, you need to come up with the algorithm. I am confident what when you know what you need, you will be able to implement it in HA (and people here will gladly help you do it).
I thought Tado X was Matter over Thread devices and just required a Thread Border Router, like the one HA can provide with a SkyConnect stick or similar.
A ESP32H2 with a Thread Border Router firmware should be able to do it too.
My guess is that Tado use the temp sensors in the TRVs to adjust the relative to each other and relative to the external sensor.
This could be if one TRV sensor report 20 and another report 18, but the external sensor report 21 and the target temperature is set to 22, then the one reporting 18 might be set higher than the one at 20, because the movement of air in the room around that TRV makes it loose heat faster.
That would make sense, although measuring the temperature near a heating element doesn’t seem like a great way to do things.
For the OP, if what you have is a large room and you want to try to get relatively consistent temperature throughout the room, consider investing in a few additional thermometers. Zigbee thermometers are pretty cheap, and I’ve found them very reliable.
It is the only way.
If you do not use the temp sensors in the TRVs, then you only have one temp sensor and that can’t be used to differentiate the set point temp on the TRVs.
I have Tado v3, not X, but they have a temperature offset. If Tado X has that too then you can use that to adjust the offset so the TRV temp matches the central thermometer. But if you change the offset too much, the batteries drain fast.
The other option is to use one generic thermostat template with the temperature sensor. If that wants to turn the heat on, you change the setpoint of the trv’s way up. If it wants to turn the heat off, you turn the setpoint of the trvs way down. No idea wht that does with the batteries.
The dowside of that method is that you lose the option to use the knob on the TRV to adjust the setpoint.
You cannot do away with the central thermostat though. Something needs to turn the heating on - just opening a valve without that accomplishes nothing. Also, by not using the central thermostat logic of the Tado, you also lose zone heating, learning capabilities to reduce overshoot, weather based optimalisations, smart on and off times, etc.
So if cloud is no go, then buying a full local but smart system like e.g. a Honeywell Evohome would be expensive, but a better option for optimal heating. It will probably save more energy too.