A servo turns the gas boiler's standard handle according to the weather. The device learns the house on its own, is not connected to the boiler, and costs about 1100 UAH.
Most owners of gas boilers in private homes set the temperature manually with a rotary knob and only change it when it gets too cold or too hot. The weather changes every day, but the knob stays in place: on warm days the boiler overheats the house and burns excess gas, while in frosty weather the house doesn't get enough heat.Our house has a Viessmann Vitopend 100 boiler, and that's exactly how it was for us: the knob had to be turned every time the weather changed. On warm days and at night the rooms became stuffy, and after a sudden cold snap it was cold in the morning until someone noticed and turned up the boiler. And when no one was home, there was simply no way to find out what was happening with the heating and make timely adjustments.Ready-made solutions don't suit an ordinary family: the manufacturer's weather-compensation automation and OpenTherm adapters require a compatible boiler, connection to its control board, and a technician's visit, while simple room thermostats only turn the boiler on and off without regulating its output. The current gas price for households is UAH 7.96/m³, so every extra cubic meter over a heating season is a direct expense for the family.
The device consists of two ESP32-based boards and is not connected to the boiler electrically. The sensor board inside the house measures room temperature (DS18B20) and uses a CC1101 radio module to receive the signal from the outdoor sensor of an ordinary home weather station (433 MHz), so no separate outdoor sensor is needed. The boiler board (ESP32-S3) turns the boiler's standard temperature knob using a servo motor on a 3D-printed mount.The controller learns the house's own "weather curve" on its own: what knob position is needed at a given outdoor temperature to keep the set temperature indoors (using the least squares method with gradual "forgetting" of old data). On top of this curve, a correction is applied based on room temperature with a 30-minute trend forecast. The knob is turned only when the calculation has changed noticeably, and no more than once every 90 minutes, which protects the knob mechanism and the actuator.Safety: the boiler's gas automation is not altered, and if power is lost the knob stays in place and the boiler operates as usual. If the indoor sensor signal is lost, the knob is set according to the weather. There is frost protection, push notifications about faults, control from a phone, a schedule, and 60 days of data history.Difference from alternatives: OpenTherm adapters and factory automation require a compatible boiler and connection to its control board; room thermostats only turn the boiler on and off; DIY servo actuators on the knob
I looked for research data to honestly assess the savings:
• BEAMA trials with the University of Salford (2021): weather or load compensation reduces gas consumption by 10–12% per season compared to a standard room thermostat.
• BRE report for the UK government (2017): modelling shows 2–8% depending
I went over what already exists once again, and how my knob is different:
• OpenTherm / eBus adapters (e.g., ectoControl): require a compatible boiler and connection to its board — habr.com/ru/articles/972592
• Factory weather-compensation automation: available only for certain models, requires a
Until now, the system mostly worked in manual mode while I was fine-tuning the firmware. Now I'm switching to AUTO mode for the entire heating season.
Measurement plan:
• once a month, take gas meter readings — which are already submitted to the gas supplier monthly anyway — and compare consumption
To avoid buying a separate outdoor sensor, I decided to use the one already at home: the remote sensor of the ASSISTANT AH-1990 weather station, which transmits data via radio signal at 433.92 MHz.
First, I wrote a separate sniffer sketch for 433 MHz and used it to figure out the sensor's signal.
The old algorithm ("heat — knob at 5, don't heat — at 0", turning when the indoor deviation exceeded 0.8°) often turned the knob and kept the temperature poorly. So I wrote a new controller:
• weather curve L = B + K·(target − outdoor): the boiler learns the coefficients K and B itself using the
Abandoned the Telegram bot: now third-party services for notifications are no longer needed. The boiler board itself encrypts messages (Web Push, VAPID keys are stored in flash memory) and sends them to phones even when the website is closed. Alerts always come through, while action notifications
While working at home, several issues came up:
• The sensor's address was hard-coded in the firmware. The router assigned the sensor a different IP address, and the boiler kept waiting every minute for a response from an empty address. Now the boiler board takes the address from which the sensor
I've been keeping this journal on the platform since today, so the first entries are a brief summary of how the project developed before that.
The first version of the system: a second ESP32 board with a DS18B20 sensor measures the temperature in the room, while the boiler board uses an SG90 micro
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Grade 11
Kharkiv, Kharkivska Oblast
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