So we spent this past weekend camping at a local spot not far from our home in Connecticut and it got pretty chili at night and so we had to use our propane heater for the first time. the heater seemed to work great pumped out a lot of heat from the two lower vents and got our got our little travel trailer nice and toasty however, when the furnace would kick on the fan that would normally circulate air from the AC would also kick on and distribute air out from the celling vents. Is this normal to help circulate the warm air throughout the camper?