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.