We'd like to install a smart thermostat in our home which is heated by a central Wood/Electric furnace (Wood being the primary heat source).
Currently, there is a group of 4 wires running from the furnace's command block to 2 thermostats on the main floor.
2 of the wires go to a simple mercury-tube thermostat which controls the dampers for the wood heat. (We keep this one at 26C so that it's always open if the fire is burning).
The other 2 wires had an identical setup (with a mercury thermostat) for the electric heat source, but a few years ago we replaced it with a programmable Honeywell thermostat so that we could program the electric heat when we were away for a few days (when we obviously couldn't make fires to heat the house). I've got this one wired very basically: 1 wire to 'R' and 1 wire to 'W'.
What we're hoping to setup now is a smart thermostat so we can see/control the electric heat from our phones when we're away. (We don't need the Alexa/Siri functionality)
Only problem is every smart thermostat I've found requires a "C-wire" which isn't present in the current configuration. The Ecobee3 Lite comes with a Power Extender Kit, but the instructions still reference control board wiring letters that aren't present at the furnace.
Is it even possible to hook up one of these thermostats?
Are there alternative thermostats that have the Wi-Fi functionality but don't require the C-Wire ?
Bonus question: For the thermostat that controls the wood furnace dampers, is it ill-advised to convert that to just a simple on/off switch?