Nest power connector not detected

[Ravik521]

Hello.

i have a nest learning thermostat 3rd gen. I have a 2 stage heat and 2 stage ac Lennox system. I do not have a common wire. 

I previously had the same thermostat, but my utility company had a sale for dirt cheap, so I figured why not get a new one. With my old thermostat it sometimes would get low battery on stage 2 ac. I figured the power connector would help.

I wired the connector exactly per the instructions. There is a c terminal on my furnace board, even though I don’t have the wire running to my thermostat. Upon installing, rebooting and updating the power connector isn’t being recognized by the thermostat.

any ideas? Thanks!

[Markjosephp]

Hello Ravik521,

Thank you for reaching out and sharing the details of your Nest Learning Thermostat installation experience. We appreciate your loyalty to Nest products and your proactive approach to taking advantage of a utility company sale to upgrade.

Based on your description, it appears that the Nest Power Connector is not being recognized by the thermostat, even though you correctly wired it according to the instructions. Since you have a 2-stage heat and 2-stage cool Lennox system without a common wire, troubleshooting the issue becomes crucial. Here are a few steps you can consider:

1. Ensure that all connections are secure and match the instructions provided. A loose connection might be the cause of the recognition issue.
2. Since you mentioned a C terminal on your furnace board, it's worth revisiting the connection at the furnace end. Ensure the Nest Power Connector is correctly installed.
3. Confirm that the power connector is receiving power. You may want to test the voltage at the connector to ensure it is within the expected range.
4. Try resetting the thermostat and rebooting the system. Sometimes, a fresh start can resolve communication issues. Also, make sure that the software is up-to-date.

If the issue persists after trying these steps, gather its power readings in the Technical Info settings. I look forward to your response.
 

Regards,
Mark

[Ravik521]

Hi Mark,

Thanks for your reply. All connections are snug and secure to the furnace board and wire connectors. I do have 2. “C” terminals that are both occupied on the board. I tried both and same response.

i installed the power connector first before the thermostat. I did do a reboot and same.  For the power connector to function, does it have to be recognized by the thermostat?

My current power levels with the system set to heat, but not running: volts 3.855, VOC 34.27 , VIN 31.36, Lin 40 mA.

lastly , the HVAC company that did install my system in 2019 did wire the power connector in when they built the system. I asked again during service when I replaced the thermostat. They confirmed it’s wired correctly per the system; and suggested to contact google as it might be a technically issue on the nest side. They confirmed the system operates as designed from Lennox.

thanks!

[Markjosephp]

Hey there,

Thanks for providing detailed information about your setup. Regarding your question about the power connector, typically, the thermostat should recognize the power source once it's properly connected. However, it's strange that you're experiencing issues despite having the power connector installed correctly.

Your power levels seem within the expected range, but it's worth confirming whether the thermostat is indeed recognizing the power. You might want to try performing a factory data reset on your thermostat and reconfiguring it again in the Nest app.

Let me know how it goes.

Regards,
Mark

[Ravik521]

Hello.

i have already tried that with no success. 

is the power levels reported consistent with what’s expected? I did try removing the c wire from connector from the furnace board and the power levels were a lot lower. I didn’t write them down. It returned to normal I suppose once I reconnected 

[Markjosephp · Accepted solution]

Hi Ravik521,

It's a bit concerning that the power levels were lower when you removed the C wire from the furnace board. It's essential to ensure that the power supply is stable for the thermostat to function properly. Once the C wire is reconnected, can you tell us its power readouts? Also, share with us a picture of your Nest Thermostat's wiring setup.

Keep me posted.

Best,
Mark