How can I improve my generic thermostat and make it get closer to the set target temperature?

Configuration
1

I have a water-based floor heating system in my house.
The valves for each floor heating ring are controlled by a ZigBee on/off switch that is registered with Home Assistant. I also have a ZigBee thermometers for each ring.

I have created Generic thermostats for each ZigBee switch + thermometer pair in my config.yaml. This works fine and I can control the temperature of my home with that setup.

However, this has some limitations. For instance - once the thermometer reaches the target temperature - the ZigBee switch accurately turns the heating valve off. However, since this is a water-based floor heating system - once the floor has been heated it continues to radiate heat for some hours after the temperature has been reached. This basically means that once the switch is off - the temperature continues to rise for some time.

This is why I had to add some automations around the generic thermostat - turn it off for 15m after heating continuously for 40m to compensate for the overheating.

Is there a way to improve this setup? Are there maybe some smarter thermostats which can automatically detect and calculate when to turn off the switch before actually reaching the target temp?

2

Your setup is unique and so are every other setup of that type.
The uniqueness is in the length of the hoses/pipes, the diameter of the hoses/pipes, the water pressure, the heat absorption in the floor and the disappation from same floor.

3

Yeah, thermal inertia is a real challenge with floor heating, and it sounds like you’ve already done a good job working around it with your automations. One option to explore is building a template thermostat or using a custom PID-based controller that can factor in how fast the temperature is rising and start cutting heat a bit earlier to avoid overshooting. You could even track average temperature deltas over time to better predict when to shut off. It’s not a one-size-fits-all since, like Wally said, every system’s thermal behavior is a bit different, but some smarter logic can go a long way in getting closer to that target temp.

1 Like
4

There is a PID controller integration.

5

I lower the setpoint (essentially switching off the heating) if the current temperature is within 1deg of target and the rate of climb is over 0.5deg/hr.

The numbers would be different for you, but it should work.

6

Maybe a trend sensor can be used. Just a wild guess though.

7

It’s a derivative sensor (was away fro my PC earlier so couldn’t look it up):

sensor:
  - platform: derivative
    source: sensor.heating_current_temp
    name: "Temp trend rate"
    round: 1
    unit_time: h
    time_window: "00:30:00"
8

It sounds like a pretty decent setup then.
You can learn a bit about how fast or slow the floor heat up and cool down, so you can adjust your timing, but other than that you would probably have to go into a lot of data collecting to get data to form a more precise algorithm.