Nest thermostat wiring help

[MikeTek]

Hi everyone in the community and thanks for helping users troubleshooting things! This community is gold.

I have a Nest 3rd generation thermostat that came with the house I bought and it started losing connectivity and saying low power. Charging it for a while helps, but clearly that's a workaround not a long term solution. So that is the 24V power...

My configuration is a cool + gas heater, both controlled by nest, fan option also. In terms of wires I have a green wire for the fan, as expected and a red Rh wire.

There is no way for me to run a new C wire from the furnace and the location of it makes working on that end very difficult. 

I have purchased a 24V adapter and videos on the internet suggest I disconnect the red from Rh and connect 24V to Rh and C. This seems to power up the system fine - but the AC doesn't kick in.

I have seen suggestions to tie the existing red Rh to the new connect I made there - but I am reluctant to do that without some advice from people that faced a similar issue.

please help 🙂

Thanks,

Mihai

[MikeTek]

just to add I obviously have the other wires there to control heat and cool - but when I put the 24V instead of Rh AC doesn't kick in anymore (system is powered fine). I take it out, reconnect the red to Rh and it works

[moralesvicente]

Hello MikeTek,

Thank you for taking an interest in our community. I’m sorry to know your Nest Learning Thermostat is losing power. Don’t worry; I’m here to assist you.

To get a better understanding of this scenario. Could you please attach some pictures of 

• the wiring system connected to the thermostat
• Power adapter

This information will be useful to diagnose the situation that you are experiencing with your device.

Feel free to reply to this post and keep me updated. 

Best regards, 

Daniel 

[MikeTek]

Hi Daniel,

here is the wiring i have (without the adapter). Per instructions, I am installing the adapter between the C connector and the R connector (currently occupied R connector. I remove that wite from there). 
the device sees the new wiring diagram, it appears to function well BUT the furnace does not engage (it says cooling but nothing happens). 
I have seen people recommend that I connect the the existing R wire also (tie it  together with the adapter wire). I am hesitant to try it 🙂

thanks,

Mihai

[MikeTek]

Forgot to add the image https://ibb.co/Jj0XrQW

[moralesvicente]

Hey MikeTek,

Thank you so much for keeping me updated. It's a pleasure to assist you.

Checking the wiring on your thermostat, it seems to be properly connected to the terminals. However, for common power troubles with this device, such as rapid battery drain, frequent Wi-Fi drops, or unexpected behaviors, you need to use this recommended Nest power connector or rewire your HVAC system and connect a C wire; you just have to install one of them. Check out this article to learn more about the Nest power connector. And how it works.

If you have this Nest power connector installed, please double-check that it is connected correctly by watching this video: How to Install a Nest Power Connector for Your Nest Thermostat.

Let me know if this information helps.

Best regards,

Daniel