All of the sudden nest needs more power?

[James-D]

I’ve had my nest for over a year and suddenly it isn’t charging. There is still power. What is the minimum power this thermostat needs? Says the wire is not connected when it is. What changed and what is the new preferred power draw?

Ive resorted to hooking up an 10 yr old Honeywell. 
Looking for answers. 

[jb76]

Hi - Nest (3rd. generation) requires 3.85 V (shown in Technical --> Power) menu in order to communicate over wifi and send control signals to your AC/Furnace. If you have a 4-wire thermostat harding running between furnace/AC and Nest - this is normally not providing a C wire to provide constant 24V power back to Nest from your furnace/AC. Instead, your Nest has been getting its power from the R (power) wire only when the furnace/AC turns on which is at most 2 volts to the Nest and only provided when the system turns on. You can try disconnecting the Nest thermostat from its base and charge it (microUSB) for an hour to get it back above 3.85 V or obtain a Nest Power Connector - https://store.google.com/product/nest_power_connector?hl=en-US&pli=1. NOTE: This NPC provides a bare minimum power to the Nest (5 V) to keep it sufficiently powered without cycling the HVAC system on/off which has been reported by users before getting the NPC installed. The alternative to this is running a new thermostat wire harness to/from your furnace using the 'C' wire to constantly charge/power the Nest.

Hope that helps.
J

[James-D]

I have 26 volts of constant power across all pairs. 
4 wire to be sure. But my transformer pushes a constant 26v to the RC. 
this has worked perfectly for over a year. 

[jb76]

Hi - can you confirm the power settings in the Nest itself (Settings --> Technical Info -->Power. The Nest needs to be at a minimum of 3.85 V to control your HVAC.

Can you also take a picture of the wiring connection to the Nest thermostat baseplate? You can also see what Nest detects as the connected equipment and wiring by going to the Settings menu on the Nest -->Technical Info --> Equipment (please provide a picture of this as well).

Thank you.
J

[zoeuvre]

Hi all, 

@James-D, oh no! I'm sorry to hear that your thermostat suddenly won't charge anymore, though there is still power in it. Are you located in North America or Europe? What type of Nest Thermostat do you have? What is the exact error message that your thermostat or the app shows? And did you try using the Help Center or troubleshooter before contacting support? If so, which steps have you tried already? Also, gather the power readouts of your thermostat's Battery, VOC, VIN, and lIN under Settings > Technical Info > Power if you have the Nest Learning Thermostat or Nest Thermostat E and VIN, IIN, PS-* under Settings > Equipment, Power Info if you have the Nest Thermostat 2020.

I appreciate your help, @jb76. 

Best,

Zoe

[James-D]

Unfortunately my wiring is in my old thermostat. I’m in Montana and it’s in the teens here. I confirmed voltage with an agent at the support desk. He gathered that the WiFi chip had gone bad and he started a warranty return. I installed the new one and it is also failing. I called back and spent an hour and a half on the phone. I was transferred to tier two. The agent said that we should wait until the weather is nice until I try troubleshooting. That would mean mid May here. I told him that was crazy and he refused to help further. 

[zoeuvre]

Hi James-D, 

Don't give up on us yet. We'd like to further check on this. Do you have the Case ID from your conversation with support? If you can provide that here, I'll look it up and see how I can continue to help. 

Thanks,

Zoe