New Furnace - Nest Thermostat Wiring Problem

[CRCFX]

Greetings:

We have a new home/system, and I'm having a problem sorting out the wiring. Currently wired to the thermostats (PRO model T705) - we have Y, G, RH&RC (jumpered) and W. 

Initially I wired Y to Y1, W to W1, R to RH to RH, and G to G. It turned on but registered an E80 wiring error on Y1, with my understanding being that it the unit wasn't seeing the 24V that it is looking for. 

I called the HVAC tech and he said it would need a common wire for power, and that was consistent with other posts that I've read. The blue wire was free, so I added that to the C terminal of the furnace and then wired that to C on the Nest thermostat. That configuration won't even turn on the thermostat. When you remove the blue wire, it 'works' as it did before with the E80 error. 

I must be missing something simple, but I can't find any answers to the problem. Hopefully someone has experience this issue and resolved it. Thank you.

[Jake]

Hey CRCFX,

My apologies for the late response. I wanted to reach out and see if you are still in need of any help? Please let me know, as I would be more than happy to look into the issue further for you.

Best regards,

Jake

[CRCFX]

Hello Jake,

Thank you for your response; I appreciate it.  We are now all set; it's working. The thermostat needed the blue/common wire, but the routing of the wire required some upstream connections to be made. The HVAC unit has a couple of boxes (upstream from the furnace) which house wires that are used to control electric dampers/zone controllers. The wires needed to be connected, there, and once they were, then the power flowed through the common wire and the thermostats are now working as they should. Thank you, again. Hopefully someone else benefits from the information. 

[GarrettDS]

Hey folks, 

It looks like we have come to a solution so I'm going to be locking this thread. If you have any other concerns or questions, please feel free to create a new thread. 

Have a great day. 

Garrett DS