I have a ten year old (propane) gravity wall furnace that came with it's own wall mounted thermostat, which is a Honeywell "Millivolt". I am now relocating the thermostat, because of a small remodeling, and want to replace the thermostat with a more up to date (looking) thermostat. Can I just go to a home improvement store and get a "universal" replacement thermostat? What do I need to know? Thanks,

Kavanaugh

What does the old thermostat have running between it and the furnace? If it is a pair of small wires, they can easily be extended to any mechanical thermostat and connected to the R and W terminals. Likely none of the newer, digital will work without a transformer. If it is more like a thin copper tube, it is a special thermostat and ordinary ones will not work in place of it. I don't know if any modern one is available to replace it.