DaleM, yes we are changing because of different fuel types. It's a "mobile" home that has been moved to another location, using LP gas. I did learn that Duo-Therm is no longer unfortunately at the beginning of my search. Thankyou for your insight into where the orifices are located however. There wasn't any real info. on the net for DuoTherm. As an update, we've opted for a replacement furnace. And I think we will happy with that decision. I'll be installing it myself so I may have more questions soon
It's made by Coleman, and is an electric unit.