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Setup 2 Google Nests in one home - Downstairs works great, Upstairs does not

rgaila
Community Specialist
Community Specialist

Disclaimer: This thread was migrated from our previous version of the Google Nest Community. You can continue to receive updates on your thread issue here or simply ask, browse or more in the new Google Nest Community.

Original Poster: Chris 3295 

I have one air conditioning unit and one furnace that serves both the upstairs and downstairs to a 1,700 townhouse (no heat pump).  I replaced our old thermostat on the first floor with a Nest about a month ago and it has worked great from day one - A/C has been working perfectly.  Since I knew it was working fine downstairs for several weeks I decided to purchase a second Nest to replace the old thermostat upstairs, even though the old thermostat was working fine and A/C upstairs works great.  As you can see by the pictures, the wiring is identical for both of the old thermostats, and I used the exact same wiring for both of the new Nests.  However, although the downstairs Nest works fine, the Nest upstairs appears to be kicking the A/C on, but barely.  While installing the Next upstairs the temp got to about 82, so after installation I set the A/C temp on the Nest upstairs to 75 but it won't get the temp below 78/79.  I let it run for 4-5 hours but it just wouldn't go below 78/79 and gets very humid upstairs.  I re-installed the old thermostat upstairs and the A/C then works fine again and went down to 75 within 20-30 minutes.  I completely wiped/deleted the Nest upstairs from the Google Home iOS app and started from scratch, re-installed the new Nest, but got the exact same results.  It seems to try to work, but just does not cool the upstairs down.  I went through the whole app installation process and the app did not detect any wiring issues at all.  Any ideas or changes that I can try?

 
 
 
 
5 REPLIES 5

GarrettDS
Community Specialist
Community Specialist

Hey there,

Sorry for the late response, but I wanted to drop in here to help. 

 

I understand it can be confusing when one thermostat is working fine but the other is not, and I wanted to stop by and see how I could help. 

 

Just wanted to double check to see if you were still needing help on this? If so, what troubleshooting steps have you tried? 

 

Please let me know. 

 

Best regards, 

Garrett DS

Chris_3295
Community Member

Thanks for replying Garrett, and yes, I still need help!  I'm not sure what to troubleshoot as both previous thermostats were wired identically, so I tried to mimic that setup when installing the Nests.  I don't have any previous experience working with electrical or HVAC projects.  After the first one worked so well I thought the second one was going to be easy to add.  I'm starting to wonder if maybe two Nests can't be used in a house that has only one air conditioning unit, and that there was something unique programmed into the previous old thermostats that allowed them to work together(?).  I'm willing to try making adjustments if you have any ideas. 

GarrettDS
Community Specialist
Community Specialist

Hey there,
Just wanted to see if you still needed help. Please let us know if you have any other questions or concerns.

Best regards,
Garrett DS

GarrettDS
Community Specialist
Community Specialist

Hey there,
Just checking in to make sure that you saw our response. Please let us know if you have any other questions or concerns as I will be locking this in 24 hours.

Have a great day.
Garrett DS
 

Jake
Community Specialist
Community Specialist

Hey all,

 

It has been a few days since the last reply, and I am going to lock the thread at this time. If you have any questions, please feel free to create a new post. 

Best regards,
Jake