That thermostat is only controlling a heater. Basically it is not wired for AC cooling. The AC cooling terminal is Y. You have a a 2-wire heating system. The red wire connected it the Rc and a red jumper connecting Rc to Rh. The power from the heating system comes in on the Red wire, and the thermostat will connect the Rh to W when there is a call for Heat. To work with a 2-wire heat only system, you must use a Nest Learning Thermostat 3rd Generation or a Nest E learning thermostat. Only these thermostats are designed to work without a common wire.
Using a nest you would set it up as a Heating System, actually, it will auto detect that. You will need to set your fuel type, ie., Natural Gas, Fuel Oil or Electric. Next you need to choose the heating type, forced air, baseboards, etc.
So go out and buy yourself a Nest Learning Thermostat 3rd Generation or a Nest E Learning Thermostat.
Ken, The AC Cooling Wizard
NestPro, Google Pro, Mechanical Engineer and HVAC service company owner.
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