Nest learning thermostat gen3

[cwon9806]

So I just bought three nest learning thermostats from costco and installed. 
First one works fine i think with reasonable battery power. The wiring is Y, G, W, R and i guess it still works without a c wire.

For the second one, i tried to do the same thing but the power did not turn on at all and I had to remove a Y wire in order for it to actually turn on. However, when I checked the battery power I noticed that the current lin was only 20(i). And said low battery so couldn't connect to the app nor wifi. 

For the third one, same thing as the second one (g, r, w) and it actually powered up and had 40 lin for this guy. I noticed that i have blue wire available for the second and the third (assuming its a c wire), but when I connect it to the C port, then the thermostats suddenly errors out.

Someone please help me out on this issue. I am completely lost

[Houptee]

You need to go the the system where all these thermostat cables connect and figure out if there is a C terminal screw.

Then you can use that extra wire as a C wire after it is actually connected to C on the system end.

[cwon9806]

okay, so having a C wire will make the battery more stable and last longer since it is powered by the HVAC system right? 

I thought these models are still designed to work without a wire though. Can I configure my wiring to (R, W, G) and make it still work?

[cwon9806]

"without a C wire"

[Jenelyn_O]

Hi there,

@cwon9806 , I saw your post and wanted to chime in. 

@Houptee , thanks for your help.

The Nest Thermostats are designed to use very little power, and in many cases, they can use your system’s heating and cooling wires to get enough consistent power. But there are also situations where you need a C-wire. If your Nest Thermostat detects that it didn't receive sufficient power, you may need to connect a common wire (C wire) or Nest Power Connector.

I would advise you to inspect your control board, as mentioned by Houptee. 

Also, please check out this article for more information.

Keep me posted.

Best,

Jenelyn

[Jenelyn_O]

Hi cwon9806,

I wanted to follow up and see if you still need help. Please let me know if you are still having any concerns or questions from here, as I would be happy to take a closer look and assist you further.

Best,

Jenelyn

[aatienza]

Hello there,

Just checking in to make sure that you've seen our responses. Please let me know if you have other questions or concerns as I will be locking this in 24 hours if I won't hear back from you again. Feel free to start a new thread and we'll be happy to help.
 

I appreciate the help, Jenelyn.

Thanks,

Archie