I have a wood burning furnace that feeds into a natural gas furnace. I'd like to add a second thermostat near the one for my gas furnace. I'd like to wire it in such a way that it turns on the blower motor in the main furnace when the house gets cool, but I want to set the main thermostat lower than the wood burner thermostat in case the wood fire gets low and the gas burner will kick in. I just don't know how thermostats are wired.