Nest Thermostat keeps disconnecting from Wi-Fi/battery level drops

[AllisonS]

Hello,

Starting about a month ago our Nest learning thermostat periodically disconnects from our network, but we’re unable to reconnect due to low battery level. At this point I remove the thermostat and charge the battery until the level is high enough to reconnect. This always seems to happen around 10 or 11 at night.

I’ve read enough to understand that the low battery level is a result of the lost network connection, but we don’t have issues with any other devices losing connection and the router is less than 10 feet away so I don’t know how it could be our router. Could this be a malfunction within the thermostat? 

[sporfrog]

Agreed it does not sound like your router!

All of this is just a long shot...

It is also possible the loss of network connection is due to low power which also results in a low battery. The HVAC system powers the thermostat. Perhaps the HVAC system is no longer supplying power due to a malfunction or transformer issue or other change? Do you know if your thermostat has a C Common wire to supply power to the thermostat? It is best to have one, but in many cases a thermostat can get trickle power in other ways. 

If you don't have a C wire considering options for adding one:

1. If there is a free wire not used - say blue - connect it to C or Common at both the HVAC unit and the Nest thermostat
2. If there are no free unused wires, consider the Nest Power Connector.
3. In some cases running a new thermostat cable with a few extras wires so that one can be used as C (common) is also an option.

At the very least check your wire connections to make sure something has not come loose.

Not sure if this is helpful but one possible answer.  Good luck!

[Patrick_Caezza]

All Nest thermostat get their power from the HVAC system by stealing it using the Y or G wires. Some HVAC systems don't like this or provide a low level of power that just barely keeps the batteries charged.

What happens is the internal battery never gets fully recharged and after a while, the internal batteries just can't supply enough power to support all of the features of the thermostat and it starts to turn features off to save power.

One of the first things that usually get turned off is because it required a lot of power in the Wi-Fi circuit, this causes the thermostat to drop offline. If you charge the thermostat using a USB power cord, it will start working again until it drops back down to a low power level.

The only solution is to install a C wire by using a spare wire or the Nest Power Connector.

[MelbaDT]

Hey folks, 

Appreciate again your informative answers, sporfrog and Patrick_Caezza. 

AllisonS, jumping in here to ensure you've read the answers above. Let us know if you have more questions about it. 

Best, 

Melba

[AllisonS]

Thank you both so much, this is great information. I’m going to try the C wire solution and see if that fixes it.

[MelbaDT]

Hey AllisonS, 

Sounds like a plan and you're welcome! Let us know if you have more questions about it.

Best, 

Melba

[MelbaDT]

Hey there, 

Checking back in — have you had the chance to install a C wire into your HVAC system already? If yes, how is it?

Best, 

Melba

[MelbaDT]

Hi, 

We haven't heard from you in a while so we'll be locking this thread if there is no update within the day. If you have any new issues, updates or just a discussion topic, feel free to start a new thread in the community.
 

Best, 

Melba