I'm about to install 3 nest thermos on a three zone system and I want to be sure I am doing this correctly. Each location has three wires, but only two were being used by the old termos (W and R). I'm not sure the third is hooked up to anything on the basement side, but I am seeing one extra wire coiled around each of the thermo wires in the basement at the Taco SR-503 relay box (top right of image - green and yellow coiled wires). Should I be hooking these extra wires up to the COM port (top left)? If so, should all three loose wires go to the same COM port?
As a plan B, I do have three Nest Power Connectors. In my scenario, is it easier to simply use those? Thanks for your help.
Thanks for posting and sharing a photo of your wiring. You have an advanced system that requires a technician to determine where these wires are connected to from your control board and which system it affects.
I suggest reaching out to a local pro to discuss your options.
Just one quick final check in here since activity has slowed down. We'll be locking the thread in the next 24 hours, but if you still need help, I would be happy to keep it open. If there's more we can do, just let me know.