Thank you Volker, I now see. I should use the condition of 'on' at the thermo to trigger the boiler and the reverse. That makes perfect sense now! As they turn on in an attempt to heat the radiator, it will trigger the energy to power on and thus the boiler. If this works in practice, it would be a great thing! I can then dump the room thermostat and simplify my heating. It does mean that any radiator can demand heat and be supplied. Amazing!
Jul 15, 2021