powerstroke73L
ArboristSite Operative
Your main furnace has a thermostat in the plenum that tells the fan to run when it gets warm enough in the plenum. No propane is required for this to happen, just electricity and heat. My house works this way, kind of hard to regulate the temp so we open windows(nice to have fresh air). I'm sure you could wire in an additional thermostat that would help regulate but that's over my head.
I don't know if you have to have a certain type of furnace for this but I have three positions on my thermostat switch "HEAT," "AC," and "FAN ON." It's a digital programmable Aprilaire.