genestealer
commented
3 months ago My Setup for Smart Heating
I'm happy to help with testing! Here's my current heating system setup:
- Thermostat: Google Nest Learning Thermostat (3rd Gen)
- Boiler: Gas combination system boiler with radiators
- Communication Protocol: OpenTherm (bi-directional communication)
Nest Controls The Nest thermostat communicates with the boiler using OpenTherm. This allows the Nest to:
- Turn the boiler on and off
- Set the radiator water flow temperature
The flow temperature is determined by several factors:
- Temperature Difference (Delta): The difference between the Nest's measured room temperature and the desired temperature you set.
- Weather Compensation: The Nest considers the outside temperature to adjust the flow temperature for optimal heating efficiency.
Nest The Nest is located in the hallway, where the radiator is always off. This means the Nest might not accurately reflect the actual temperature in heated rooms.
However, I have integrated the Nest thermostat with Home Assistant as a climate entity, allowing for more granular control. I don't use the scheduling function on the Nest itself, relying entirely on Home Assistant for a more sophisticated "away" mode and other automations.
Room Control with eTRVs Each room has an electronic thermostatic radiator valve (eTRV) that can be controlled through Google Assistant via Google Home speakers or displays. This allows for individual room temperature adjustments. I also control the "Nest" (hallway thermostat) through this method, effectively turning the boiler on and off.
Current Manual Operation Currently, all eTRVs are set to "auto" with a base temperature of 8°C. To heat a specific room, I manually adjust the eTRV temperature to the desired level (e.g., from 16°C to 18°C).
I also need to manually adjust the Nest thermostat to a slightly higher temperature (0.5°C to 1°C) than the current reading (e.g., Nest reading 17°C, adjust to 17.5°C-18°C) to trigger the boiler to turn on and heat the room.
Automation My plan is to leverage advanced scheduling add-ins within Home Assistant. This will enable me to create individual room temperature schedules ranging from 8°C to 18°C, depending on the time of day.
I plan to create automations in Home Assistant that monitor the requested eTRV setpoints and actual room temperatures. These automations could potentially incorporate data from additional room temperature sensors. When the room temperature falls below the eTRV setpoint by a specific hysteresis value (between 0.5°C and 1°C, to be determined), the automation would trigger.
However, due to OpenTherm communication, simply "turning on" the boiler isn't possible. Instead, the automation would need to adjust the Nest setpoint to a specific value ("x") above the current room temperature.
Calculating "x" for Optimal Flow Temperature I plan to calculate "x" as a weighted average based on the delta temperature values from all eTRVs in rooms requesting heat (i.e., rooms where the actual temperature is lower than the eTRV setpoint). Essentially, a larger delta (greater difference between room temperature and desired temperature) would result in a higher "x" value. This, in turn, would signal the Nest to set a higher water flow temperature, allowing for faster room heating. For example, a 1°C delta might trigger a 40°C flow temperature, while a 10°C delta could result in a 50°C or 60°C flow temperature.
Achronite
This change would introduce the capability to link the underlying state of the heating system (e.g. 'heating', 'off') to the state of radiator valve.
It could work initially by getting the boiler status from a linked MiHome thermostat (using act_t) and using config.json.
But support for other smart system integration (e.g. Wiser, Tapo, Nest) system setting should be investigated and implemented if possible.