Grounded C Wire issue

[ethanstuber]

Hello, 

I have a 3rd gen Nest Learning Thermostat that has been having issues with the heat short cycling (runs for about 5 mins and shuts down, get a delayed for "# of mins" message on nest). No issues at all with the AC side, has been running fine since install.

The furnace was inspected by a heating company and they see no issues. I have spoken to the nest help line and they have determined there is an issue with my common wire. I did a reading on the common wire for voltage using a multimeter and am receiving a steady 26.1 v across the C and R wires and at the control board in the furnace.

I have seen a lot of people mention its a power issue with this issue but no clear resolution, trying to figure out where to go from here? Is it possible that a bad ground would cause this (that's what nest help says the issue could be)? The main control board for the furnace is grounded to the frame of the furnace with a wire. 

The furnace, AC unit and all equipment are about 1 year old. Nest worked fine for about 6 months and then i started getting the issue. 

Any insight would be appreciated.

Thanks, 

Ethan 

[ethanstuber]

I found this which seems to be very similar to my issue besides run time on the furnace. But there's not a resolution here: https://support.google.com/googlenest/thread/16168375/common-wire-to-be-grounded-issue?hl=en

[Jake]

Hey ethanstuber,

I am sorry for the late reply. I wanted to follow up with you and ensure you are good to go. Please let me know if you are still having trouble with the heat short cycling. I also did find a helpful article with some troubleshooting steps that you can review. Let me know if that helps.

Best regards,

Jake

[ethanstuber]

Thanks yeah I still have the issue. I havent found a solution to whats causing it, replaced the flame rod in the furnace, had the system serviced, tech said everything is running properly on furnace, full 24v coming through the C wire to thermostat. 

I'm going to try buying a cheap $20 honeywell thermostat and verify that can keep the heat running. 

[GarrettDS]

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

I understand that these issues can be confusing but I definitely 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? Were you able to figure out if you are still able to heat with a honeywell thermostat? What other troubleshooting steps have you tried?

Please let me know.

Best regards,
Garrett DS
 

[ethanstuber]

Testing tonight will report back....If you the thread above you can see what i have tried already, plus i have talked to nest troubleshooting who has told me my c wire is not properly grounded (whatever that means for a low voltage wire). 

[Jake]

Hey ethanstuber,

I just wanted to follow up once more and ensure you are good to go. If your C wire is not properly grounded, there is a chance you are losing power, and that is why you are running into the issue.

I would recommend having a Nest Pro come out and take a closer look. They would be able to double-check the wire and ensure that the Nest Thermostat is installed and good to go. Please let me know if you have any questions from here, as I would be happy to take a closer look and assist you further. 

Best regards,
Jake

[Jake]

Hey ethanstuber,

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