The first attempt to install on the bedroom element failed .. failed 30min before I gave up. It complained of stroke during calibration. Solution later, you have to reset the thermostat so it understands that you have started over.
Made on another 2 elements and it took 5 min each and went on the first try.
Have been driving for a few days now and it really works.
Has no smart control of the boiler yet so it is not optimal to have the boiler at 21 degrees and thermostat at 19. That is, always have the boiler warmer than the warmest room.