The problem with the overshooting really seems to be dependet if your heater runs 24/7 or if you stop your heater over night.
Looks like this thermostat tries to be more “smart” than I thought.
It tries to calculate how slow a room heats up and how much energy it needs to hold the temperature.
Most likely looking at the data of the past few yours, or the last day that it internally collects.
If you now shut down your heater over night, and the room temperature drops a little bit over the time, the thermostat will start to open the valve more and more.
But as the room temperature drops more instead of the room warming up, the internal calculation of the thermostat goes mad.
When the heater starts again, the thermostat will calculate the needed heat completely wrong and the room temperature will overshoot by a lot.
How much depends on the room size and the actual flow temperature in your heating system.
Long story short:
If you have times where your heater is stopped, create an automation that will reduce the target temperature for the thermostats for that time.
Better do NOT use the “off” state instead of reducing the target temperature (which would be easier as you wouldn’t have to save the real target temperature value somewhere):
There’s a bug in the firmware as described a few times in this thread, so the thermostats often start to heat again after a few minutes even that they still report an “off” state over the Zwave network.
I’m now really happy with the thermostats, since I made these changes.
EDIT:
Oh and one more hint:
Like with every smart thermostat, using a better placed external room temperature sensor helps a lot to keep the temperature stable. The larger the room, the bigger is the benefit.
You will see a way more stable room temperature and a lot less jumpiness in the valve control.
Which results in a more comfortable feeling.
There are two ways to do this:
- Use the official external sensor feature of the thermostats by settings temperature offset to -128
- Calculate the offset yourself and write that as offset compensation into the thermostat.
For both are solutions in this thread:
The first way is the official supported and is most likely easier to set up.
I use the second one, as it still uses the internal sensor, just with a little shifting.
So if Home-Assistant (or the external sensor) dies, the thermostat will still be able to detect room temperature changes.
It will heat the room a little bit to much or too less, but it won’t freak out completely because of missing room temperature updates.