Nest Thermostat - STAY AWAY

[JensR]

To Whom It May Concern:

I purchased a Nest Thermostat in August of last year and was never told that it runs on batteries. It was hooked up to my 24V power from the AC system and I thought the two supplied batteries were for back-up.  That appears not to be so and after only a little over a year I get intermittent low battery warnings that go away again.

This is the second unit I purchased, after the first one had manufacturing issues and never did work - now this replacement has battery issues after barely being outside the warranty period. I spent hours on the phone with the first unit, until they finally told me it was a hardware issue and not my home wiring.

In over thirty years of owning houses the thermostat was never an issue, but this unit is terrible, so I recommend staying away from these units and to buy one where the battery truly acts as back-up in case of a power failure.

Support was not helpful either.

The next unit I buy will be Honeywell or another manufacturer, not a Google device for sure!

[David_K]

Nest Thermostat (2020 model) is not designed to run on batteries. Like you mentioned, in normal operation it receives power from your HVAC system.

However, if you're repeatedly getting low battery messages, or if there’s another power-related message on the thermostat, for some reason the thermostat is not getting enough power, and so it will use the backup batteries in those cases. 

As another user, not Google employee, we're not privy to those conversations you had with support of course, but it's curious it's being coded as a hardware fault. 

Some systems, including heating-only, cooling-only, zone-controlled, and heat pump systems, require a C wire or the Nest Power Connector. I'm wondering what type of system you have, and whether you have a C wire or power connector installed?

[JensR]

Hi David, that was the other issue, I had the Nest professionally installed and it took them four visits to get it right last year. I had purchased a connector just in case, but they said I had a C wire. After the install finally worked, the unit worked fine for about a year until the Nest said I had a critically low battery yesterday and then five minutes later when I had support on the phone, the battery showed fine and fully loaded again. I have a combined AC and heat pump unit that worked without issues on a non-wi-fi Honeywell thermostat for years. The Nest support team yesterday told me, I should have known I bought a battery-operated thermostat, which makes no sense.

[David_K]

Yeah, that's rather perplexing. If you go into the thermostat menu, are your voc, vin, and lin power values within the required ranges?

Nest thermostat information menu - Google Nest Help

See the "On your thermostat" then "Power" section in that article.