using furnace fan to distribute heat from fireplace
Normally I am heating my house with a heatilator fireplace. The basement is cold though. I want to set the furnace thermostat to 70 F. and when the room with the fireplace, which also has the furnace thermostat, reaches 70 F. I want the furnace fan to come on but no heat from the furnace. When I am not going to be home for an extended period in the winter I want to flip a switch and have the furnace work normally to prevent the house from freezing in the winter. The current thermostat is a mercury switch with only 2 wires going to it. No switches at all except the one for the temperature. The return air also happens to be near the fireplace.
Run new thermostat wires. Then get an auto change over thermostat. Wire it in. Set the cooling temp to 73, and the heating temp to 70. Then when the room temp reaches 73 the fan will come on, when it drops to 70, the furnace will take over.
Thank you. I will probably set it to 60 for heat and 70 for cooling. I see the two wires are hooked up to 2 of the 5 screws on the control box of the furnace. The screws are labelled with letters. Do I just match the letters on the thermostat with the letters on the control box? Do I use 5 conductor wire?