v2021.11.8-beta1

[ScratMan]

Development version adding optional min_cycle_duration (default value is 0) to filter short on/off cycles for heating systems requiring a minimum on or off time (like boilers).

Full Changelog: 2021.11.7...2021.11.8-beta1

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This discussion was created from the release v2021.11.8-beta1.

[nagyrobi]

I made this for scheduling: https://github.com/nagyrobi/home-assistant-configuration-examples/tree/main/heating looks like your component was the missing puzzle.

[nagyrobi]

It's a little undershot but it works nice with the 10-minutes minimal cycle:

In the house the feeling is a whole lot better! No more warm and cold waves.

I'll try with an autotune in the next few days.
How does changing the target temperature affect the autotuning?

[ScratMan]

I missed your message, sorry. The Autotune now (in beta 4) waits for a few samples to measure the sampling rate of the sensor, then takes the set point of the thermostat and starts regulating the temperature like a standard hysteresis thermostat to analyze the behavior of the system. No need for a step anymore. And you can't adjust the set point till autotune has finished.

As your sampling rate is high (30s), you should keep the 0.5°C noiseband, and on the last beta release (2021.11.8-beta4) a 6 to 10 hours lookback period gave good results.

[nagyrobi]

I will try. Thanks.
Should I remove the sampling_period setting during autotune?

[ScratMan]

No, you can keep it.

[nagyrobi]

Maybe worth considering two cycles, separate cycle off and cycle on?

[nagyrobi]

This could be nice with some advanced calculations, to assume based on the elased time the position of the valves and then wait with the pump a dynamic time... but that's a whole other story.

[nagyrobi]

To keep backwards compatibility you could have min_cycle_duration as it is now, and add a separate optional min_off_cycle_duration too.
And then:
if min_off_cycle_duration not specified, then min_off_cycle_duration = min_cycle_duration.

[ScratMan]

Understand. I will update with your proposal with a min_off_cycle_override that would be considered only if min_cycle_duration is set.

[ScratMan]

Hello, min_off_cycle_duration is implemented in release 2021.11.8-beta2. I also modified the autotuner trying to improve it for better stability and easier debugging.

[nagyrobi]

Thank you.

[nagyrobi]

Based on a 24-hour test, this is what I see:

The pink line shows the target temperature being adjusted on schedule.

What parameter do you suggest to be adjusted in order for the ramp up to be faster (=do not stop the heater until it reaches the target temp)? The effect is that all schedules need to be shifted in advance with 1-2 hours...

[nagyrobi]

My config currently is:

  - platform: smart_thermostat
    name: Fűtés
    heater: switch.kazan
    target_sensor: sensor.atlag_belso_homerseklet
    min_temp: 16
    max_temp: 26
    target_temp_step: 0.1
    min_cycle_duration: '00:08:00'
    min_off_cycle_duration: '00:11:00'
    keep_alive:
      seconds: 60
    away_temp: 20.5
    kp: 180
    ki: 0.050
    kd: 30000
    pwm: 00:10:00

[ScratMan]

Hi, please try with reduced Kd, by 10% or 20%. This should allow the heating to continue a bit more during the rise of the temperature.

[ScratMan]

It also looks like your sensor returned many samples per hour, you may limit the number of samples used for the PID using sampling_period parameter to limit to half or third the count, it should smooth the on/off curve.

[nagyrobi]

The sensor sends the current temperature value every 30 seconds for precise measurement. What's your recommendation for sampling_period in this case?

[ScratMan]

It will depend on the max slew rate of the temperature when heater is at 100% for a long period. If it takes 1 hour to do a 1°C step, I would say 10 to 15 minutes for sampling_period should be ok, but if it takes 10 minutes, you should rather set it to 2 minutes

[edouardkleinhans]

@ScratMan, do you have any recommendation regarding min_cycle_duration for a gaz boiler ?

[ScratMan]

Sorry, but no, I can't recommend a value. You should check the start time of your boiler from relay on to hot water output. The minimum cycle should be over this time.

[nagyrobi]

@ScratMan, do you have any recommendation regarding min_cycle_duration for a gaz boiler ?

For a gas boiler 10 minutes is safe enough as min_cycle_duration to avoid damage and also get good heat out of it. That means it's gonna turn on and off at most 6 times per hour (3 times on and 3 times off).

[edouardkleinhans]

so i need to set min_cycle_duration to 10 minutes. But what about PWM, do i need to set it to 10 minutes too ?

[nagyrobi]

I have set mine that to 25 minutes.

[ScratMan]

The code will need an update to improve modulation with minimum cycle duration, so that the on time is adjusted when control_output * PWM / 100 ≥ min_cycle_duration ; and fix on time to min_cycle_duration and adjust PWM duration (off time) when control_output * PWM / 100 < min_cycle_duration