I have a nest learning thermostat hooked up with the common wire to my propane heating system as a back up to my heat pump(heat pump controlled by another thermostat). The heat pump is the system that has been heating my vacation house and has been doing so well for the last month, however, this is the 2nd time that the Nest has taken over and is pulling heat way over its set temperature (as far as I can tell the thermostat should never have turned on) and my temperature is now 69 degrees while the unit is set for 55 degrees (the heat pump keeps it at 60 while we are away). The last time that this happened I had to take off the thermostat and the base plate in order to get it to stop calling for heat from the boiler. I have another unit on the 2nd floor that I have not had this problem with and it has been hooked up for over a month. As I am not in the house at present I am very frustrated with this. I got this thermostat when I had the propane boiler installed and when this happened the first time the installer changed the setup to use Taco zone controller and it seemed to fix the problem but now as mentioned the heat is rising in the zone that is controlled by the same nest t-stat. Is it possible that the nest has a defect that continues to pull the power from the wrong wire on occasion? When I look at my technical info for the nest the battery is at 3.93 volts which I believe is a good level.
Please let me know how to proceed, I wanted the nest so that I could monitor the house remotely and it is great from the perspective but very frustrating when I am heating beyond the set temperature and using a more expensive option when I don't want/need to do so. And now I will need to make a special trip to the house to rectify this.
--Paul
