nest

Hi, My old mercury thermostat (2 wired) recently died and replaced it with a Nest Thermostat 1st Generation (2020). I have a Burnham ES2 Series gas fired boiler (Model # ES24BNI-T). After installing my Nest thermostat gave me an error N260 indicating that a C wire is needed. My thermostat is...

1 zone per floor --1st floor zone 1, 2nd floor zone 2 and basement zone 3 .. nest thermostats on 1st and 2nd. i DO NOT want a thermostat in cellar. right now cellar(3rd zone) has a modine that comes on when 1st floor calls for heat BUT we have a fireplace which keeps 1st floor from coming on...

I have a Navien NCB-240E connected via two wires to a traditional thermostat and all is well. I wanted to replace that setup with a Nest. I can run a new wire from the NCB-240E to the Nest. I'm unsure of what type of wire to use and where the connections should go. I can follow wiring...