Here’s an example of the longest cycle I was able to achieve.
Green - flame on
Yellow - relative modulation
Blue - boiler flow temperature
That SAT settings were set as follows:
However, the next cycle was not as long, i.e. the relative modulation curve (yellow) where it goes up and down was not achieved (similar to the previous two cycles on the screenshot).
I run some more tests. My configurations for various scenarios maybe were not as intended by SAT, but it looks like SAT prioritises the precision of being close to the target temperature and prevent overshoot, which means that cycles are shorter than they can be. The screenshot below, between morning and about 4pm, runs shorter cycles but more precise target temperature. After 4pm, I prioritised longer cycles by increasing the coefficient to the maximum and lowering max CH temperature, and it seems to work. However, I needed to add an automation to stop the heat when target temperature was reached.
Here’s another graph from this morning, which prioritises longer cycles, and it’s working well. I can get longer cycles consistently.
Here, you can see, that when a longer cycle is prioritised, the control setpoint is ever so slightly lower than the boiler flow temperature.
Likewise, for the shorter cycle, the boiler flow temperature is ever so slightly below the control setpoint, and causes early termination of the cycle.
So my question is, would be possible (as an option in config) to prioritise longer cycles, and then as a secondary priority, prevent target temperature overshoot?
If I understand correctly, with longer cycles, I get better efficiency overall, because of improved condensation conditions, higher delta, etc.
Some extra screenshots, representing current state
hvac_modes:
- "off"
- heat
min_temp: 7
max_temp: 35
target_temp_step: 0.1
preset_modes:
- none
- activity
- away
- home
- sleep
- comfort
current_temperature: 18.4
temperature: 20
current_humidity: 74
hvac_action: heating
preset_mode: home
error: 1.58
integral: 0
derivative: 0
proportional: 112.622
history_size: 63
collected_errors: 1
integral_enabled: false
pre_custom_temperature: 19.7
pre_activity_temperature: null
derivative_enabled: true
derivative_raw: -0.0
current_kp: 71.28
current_ki: 0.000974
current_kd: 128736
rooms: {}
setpoint: 44
summer_simmer_index: 21.2
summer_simmer_perception: Slightly Cool
warming_up_data:
error: 1.58
boiler_temperature: 44.8
started: 1703580000
warming_up_derivative: 3.66
valves_open: true
heating_curve: 72
minimum_setpoint: 44
requested_setpoint: 184.6
adjusted_minimum_setpoint: 46
outside_temperature: 5.9
optimal_coefficient: 13.7
coefficient_derivative: -0.1
relative_modulation_value: 0
relative_modulation_state: warming_up
relative_modulation_enabled: false
pulse_width_modulation_enabled: true
pulse_width_modulation_state: "on"
pulse_width_modulation_duty_cycle:
- 450
- 449
friendly_name: OTGW2
supported_features: 17
Heating this morning
Could you please advise what do you consider one cycle to be? Is it not the duration of the flame being on?
A PWM duty cycle is considered the combination of heating_on and heating_off in given intervals. Here and here you can find some more infos about how we calculate the PWM duty cycle ON/OFF times and how we extend the 15 minutes interval, a feature called Automatic Duty Cycle.
I noticed that the Max CH setpoint command e.g. SH=55 is not always respected by the boiler but sending GW=R followed immediately by e.g. SH=55, helps. Maybe it’s the same with Max Modulation?
No, I can see from the graph that the Max Relative modulation sensor drops to 0% ( correct behavior ) but your boiler doesn’t respect the instructed command.
The SAT works well in terms of keeping to the target temperature and making the boiler work more efficiently. However, I still seem to struggle to get the perfect cycle consistently.
In my previous post, lowering the coefficient to 0.1 only worked temporarily, then cycles were short again after a while. What would perfect cycle look like when looking at the relative modulation and boiler temperature look like?
A perfect cycle should have AT LEAST a duty cycle of 3 minutes heating ON
and the rest heating OFF ( In 15 minutes intervals). Note that we continuously monitoring the boiler flow water temperature in order to calculate the PWM duty cycle. As a result the higher boiler flow water temperature the shorter the ON cycle.
With the dynamic minimum experimental feature, it seems to work but on many occasions, the cycle is too short because of the minimum requested setpoint, I think?
If your radiators aren’t equipped with TRVs, please uncheck this option.
My configurations for various scenarios maybe were not as intended by SAT, but it looks like SAT prioritises the precision of being close to the target temperature and prevent overshoot, which means that cycles are shorter than they can be.
That’s why we use a thermostat 
! We try to keep the temperature as close to setpoint as possible, while monitoring every moment the outside temperature, room temperature and the boiler flow water temperature.
Bonus:
This is a graph of a SAT user. He managed an incredible accuracy of 0.01! Moreover you can see the PWM ON/OFF cycles.
Thank you so much George (sergeantd83) for your comprehensive and insightful responses to all my queries about the SAT. Your explanations, especially about the PWM duty cycle have been incredibly helpful. I appreciate your patience in guiding me through the nuances of the SAT system.
I’ve set SAT to the recommended settings. The results are fantastic! Both the boiler and thermostat are functioning excellently, maintaining the perfect temperature with impressive efficiency.
Here’s my snapshot of the last 15min, this is in a 150m2 house, so SAT is very impressive 
You are welcome! We are very happy that your SAT instance is up and running as intended.
Hi All.
For those of you who want to see SAT in real time, you can see my real-time boiler data here - Real Time Ideal Logic Heat H24 Performance Data
I’m still tinkering with heating schedule variables and you can read more about those test conditions: Show and Tell Discussion #40 (github.com)
My gas boiler smart meter readings lag by about 1-2 hours, so efficiency should only be read when the heating has been off for a while or at the end of the day.
My target room temperature (Summer Simmer Index) is 21.9°C at night, slowly rising in the morning and throughout the day to 23.5°C.
If data shows Flow Temp higher than 60 it means that DHW is on.
Made possible by - My gas boiler data is live! - Emoncms - OpenEnergyMonitor Community
Enjoy!
