I bought some Netatmo smart radiator valves recently. Our building has communal heating so the hot water is always on. When I installed them to replace the three Drayton TRV4 in our flat, things got a bit toasty: all the radiators were pumping out heat and the temperature rose wildly above the setpoint (16C to 24C).
Thermostatic radiator valves have a little pin that gets pushed in and out by the thermostat: out is “on”, in is “off”. This meant that the smart valve wasn’t pushing the pin all the way in.
The Netatmo app has a Calibrate button which moves the motor inside the valve to detect the minimum and maximum position of the pin. When run whilst not attached to a radiator you can see the plunger move all the way out and all the way in. Presumably when attached to a radiator it moves the plunger until it feels some resistance, then moves it until it feels a lot. I guessed that this detection was not finding the true end of the pin’s movement since the calibration process finished rather quickly: the motor could be heard moving out and then in shortly afterwards.
The solution: oil the pin! I used WD40 on the pin and quickly pushed it in/out for a minute, after which it moved a lot more easily.
After reattaching the valve the calibration process took a lot longer and consisted of five discernable motions: out, in, out again, in again, then finally set the position to “off”.
Perhaps this seems obvious in retrospect but I couldn’t find much info on the internet!