In other words, don't buy it.
Purchased Nest Learning to control both Heat (boiler) and AC (older system) in New England. Installed 1 Apr 21. Used heat and AC through mid June before transitioning to summer AC. While getting ready for winter on 6 Oct 21, turned on heat and controller in TACO box (interface between thermostats and boiler) just kept clicking. Called HVAC Co for PM and troubleshooting. No issue with boiler. Nest giving N72 error - no power to heat Rh wire (not true). Tech bypassed thermostat and started boiler. Contacted Nest - given unbelievable run around, including sending part that they knew wouldn't fix it. Contacted again today (10-29) and given same run around. Won't acknowledge problem or propose solution. Blames me. This is a common problem and not unique. Save the hassle and buy another brand. You can thank me later.
I'm having a similar problem. Taco fires the water boiler fine (no Nest), but at times has issue when the Nest calls for heat. Taco controller would just click and not fire the furnace. Did you ever figure out this issue? Thanks!
I'm sorry for the trouble this may have caused you—let's see what's going on.
It appears that you are experiencing a power issue on your Nest thermostat. A few questions: could you tell me the wiring configuration of your thermostat? Also, are you getting any wire reports or message codes?
Have a look at this guide to troubleshooting and let us know how it goes.
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.