About this deal
Remove the motherboard of the old 2 wire thermostat and put the new 2 wire thermostat in its place.
The most common type of 2-wire HVAC system is a forced air system. In a forced air system, the furnace blows heated air through ducts in the house and into rooms. The blower fan in the furnace is usually controlled by a thermostat. When the room reaches the desired temperature, the thermostat turns off the blower fan. A forced air system can also include a central air conditioner. List of two-wire smart thermostats and Specification Specification Take off the motherboard and secure the wires; if you don’t hold them, the four wires will get lost in the wall. So, the wire going to the existing term 3 is the Live feed so that should now go to the 'com' terminal on your new stat.B” is for reversing valve heating. Some producers like Rheem energizes the reversing valve when the heating mode is on in heat pumps. A dark blue “B” wire is needed for the t-stat terminal. Thermostat Green Wire (“G” Wire)
These thermostats are typical for heat pumps: HVAC devices that can cool and heat. To produce the airflow, a fan is needed (green wire). If you have properly reconnected the 2 wires, the new 2 wire thermostat should control the furnace in the same way your old 2 wire thermostat did. 3 Wire Thermostat Wiring (Boilers, Heaters) Knowing how to wire a 3-wire thermostat is fairly easy compared to 4 and 5-wire thermostats: 4 Wire Thermostat Wiring (Heat Pumps, HVAC)Take a photo of the wires; you can also label where each one goes, but taking a photo is much easier. Spreading them apart will create at least a 2×2 inch crosssection, and the wires will be suspending on the wall (instead of on the thermostat). Great thermostat which I required for existing two wire supply, couldn't find one like it anywhere else. White wires are for heating. You will find them in gas furnace thermostats, for example, but won’t find them in air conditioner thermostats. HVAC technicians know the color-coding by heart; they can just remove any Honeywell thermostat, replace it with the new one and reconnect the terminals.