Pull the inside panel to get access to the air box inside the RV. Check to insure that the ducts are hooked up and than none of the duct ports on the air box are open with no duct. Your furnace should be able to keep up at those temps. If the air flow was too low, the furnace would shut down due to over heat. If the ducts are not connected properly, you cold have a nice warm underbelly, but cool living area.
2015 Freedom Express 248RBS
TV 2015 Silverado HD2500 Duramax
TST Tire Monitors
Honda 2000I + Companion
2 65W solar panels