We have three Nest thermostats. Two Nest E Thermostats were installed in January 2020. A Nest Learning Thermostat was installed in February 2023, less than a year ago.
In January, a storm took out our Verizon internet service for about 24 hours. When it was restored, the two Nest E thermostats came back online immediately and automatically, but the Learning Thermostat would not re-connect. We have a Deco mesh WiFi network. The room with the Learning thermostat is large and has two mesh routers, one about 15-20 feet from the thermostat. But one of the Nest thermostats is even further from its nearest router, and has had no issues in the 4 years.
The Learning Thermostat had given no hint of trouble before this WiFi outage. Even when the heat did not run all summer (thus presumably not charging the battery), it worked fine as soon as we needed it in the fall.
I read the trouble-shooting articles and spent a couple of hours trying various things. At one point, I removed the thermostat from the wall and charged its battery because the thermostat said the battery was too low to reconnect. That did not work. I put the problem aside for a couple of weeks.
Yesterday I spent another hour or so trying to reconnect, and could not. The thermostat says it cannot see any networks, and will not recognize our network when I type in the name. The voltage yesterday afternoon was 3.719 volts. The online articles say that the thermostat will not reconnect unless the voltage is at least 3.8. What puzzles me (and quite frankly annoys me) is that the weather was super cold on Saturday and Sunday, so the furnace ran for many hours over the weekend. It must have run for at least 12 hours on Sunday, because we were using the room for much of the day, and probably ran occasionally into the wee hours of Monday. The room is large with big old drafty windows and a high ceiling, so even maintaining nighttime temps requires frequent furnace operation. My understanding is that the thermostat charges when the furnace runs, so it should have been as fully charged on Monday as it ever will be, by the weekend's activity.
So, looks to me as if the Learning Thermostat is not charging its battery sufficiently, and consequently won't connect to WiFi. The older thermostats are OK, even after 4 years. Is there something about the newer thermostat that makes it less able to charge? Or maybe fussier about the minimum voltage to connect? Should I try to get the Nest Learning Tstat replaced under warranty? I really need this thermostat to work on WiFi and it does not seem able to do that anymore.
One possibility that occurs to me is to switch one of the Nest Es with the Learning Thermostat. One of the Nest Es is in a zone that runs more often, so maybe the thing would get charged enough in that location? But reassigning them to other locations sounds like a possible hassles, and I do not want to mess up another zone...
