My heat-only system only has two or three wires connected to the thermostat. Am I compatible with ecobee?
Old thermostat has wire 1, 2 & 3. Which smart thermostat is compatible? : r/electrical
What if I don't have a C-Wire? – Smart Thermostat Guide
Cync Thermostat Wiring Configuration and Installation Guide
DC 12V 3 Draht 2 Kanal LED Digitale Thermostat Fan Temperatur Control Motor Speed Controller Gouverneur Schalter NTC Sensor summer _ - AliExpress Mobile
Wiring Nest from 3 wire honeywell thermostat : r/Nest