Since I'm in a class C, the dash heat would not circulate and there is no "fan only" option on the furnace. That is why I replaced the return air grill with dual window fans. I've tested them to -27 c (-17 f) and there were no freeze ups of the fresh water system. The fans draw a scant 27 watts so it is easy to run them from an inverter.
Huntindog wrote:
Another point. Most TTs use the furnace to keep the tanks/plumbing from freezing. In my TT, this would work down to about 6 degrees. (YMMV). That was with the furnace running. If I were to use electric heat instead, the tanks/plumbing would freeze at a higher temp.