Our house has an old boiler, and the thermostat isn't working. I'd like to replace it with a Nest thermostat. But, when I took the cover off to check which wires it had, I only see two wires (red and white) and they aren't marked. I checked the Nest compatibility guide, but it asks me to identify the wires, and I have no idea which ones they are.
Can anyone tell me how I can figure out which wires they are? Could I install a Nest E thermostat on this?