[DutchmenSport]

Originally Posted by DQDick

When you open the basement wall, behind the furnace you will probably find a plenum with connections going to the various ducts. I would be surprised if one or more of the connections haven't come loose. Several folks have had that problem.

I also agree with this assessment. When I removed the wall in my basement, I was very surprised what I found under there. I had a couple of those flexible duct hoses that had popped off the furnace, and I quickly discovered how the underbelly is "heated" ... um .... smaller lines coming from the furnace and just open on the end, blowing under the floor. No wonder the camper uses so much propane to heat the thing, probably 50% of the heat is blowing under the floor into that open space .... thus.... the winter package and good to zero degree temperatures ..... oh yes????

It's possible your air ducts are adjusted in a similar way, to keep the pipes from freezing in zero degree weather. Some sections UNDER the floor need more heat than others to prevent the lines from freezing, as in those locations the water lines and sewer lines and holding tanks are located. My guess. But you'll be SHOCKED how much heat goes under the floor.