I went and turned the furnace on Thursday and set the thermostat at 40, I have the RV winterized so this was just for precaution it was supposed to get down in the teens the LP gauge showed 2/3 tank e...
The propane is stored in the tank in liquid form. It has to change to a gas to make it to your furnace. That takes heat. It is possible that when it is really cold outside, there is not enough heat to evaporate the liquid to a gas fast enough to keep the furnace running.