If you live in Europe, your heater highly likely has OpenTherm (which is not as open as the name suggests). So instead of playing with lego you can buy/build a

If you live in Europe, your heater highly likely has OpenTherm (which is not as open as the name suggests). So instead of playing with lego you can buy/build an otgw[0] which will MITM your heater and thermostat communication, allowing you to add your own smart solution on top. You can still use the outdoor temperature sensor (if installed), thermostat control logic, etc. But you can intercept and rewrite commands so you can set temperature, date/time and other heater/thermostat settings. And snoop on messages like internal temperatures from the heater and things like water pressure. [0] http://otgw.tclcode.com/ http://otgw.tclcode.com/