I have a new Gen 3 Nest Thermostat and am finding that even when I have the Heat set to 68, it reports (and heats) well past that, often into the upper 70's (currently shows 78!). The new Nest was part of a Heat Pump replacement, but it seems it's not controlling properly. Is there a way to set a "don't heat beyond ## degrees" temperature?
That would be impossible to do 🙂
The Nest will send out either on/off or OpenTherm instructions to your heater. The heater will respond by - heating. This involves pumping around water through either your floors or / and radiators. If the desired temperature has been reached, the Nest will signal the heater to stop heating. However, the water in your system is still warm (or even hot) and so the temperature may continue to rise. The Nest will signal this and - at least that's my assumption - try to compensate for it by switching off the heater earlier next time, or - in case you use OpenTherm - signal the heater to lower the flow water temperature.
So, especially in smaller rooms and with new Nest installations, it may well happen that your temperature rises above the desired temperature. Initially. It should, however, be corrected after a while.
This, of course, assuming you haven't made a wiring error, the Nest is defect, the heatlink is defect, the boiler or heater is defect - there are many ways this can go south.
Thanks for assisting, @fortean.
@kf6spf, I appreciate you posting and updating us on your efforts to address your concern and find a fix. I wanted to ensure that everything was covered here.
I found an article that might help if your heat pump has an emergency heating. If there’s anything else I can help you with, please let me know.