As the fall season rolls around, many RV owners start winterizing their vehicles and storing them away until spring. However, if you’re someone who enjoys year-round camping or living in your RV full-time, it’s important to prepare for the wintry weather ahead. To combat the cold temperatures, make sure to keep your propane tanks full as LP use is essential in this case. Nevertheless, despite taking precautions, have you ever found yourself waking up in the middle of a freezing night with a furnace that won’t work? If so, you may have assumed that you ran out of propane. This is a common concern for those of us who love winter camping and dealing with wintry weather conditions.
When you buy propane, you are buying a liquid that has been compressed approximately two hundred and seventy times. So, the propane molecules are cold and tightly packed into the propane cylinder. In other words, those propane molecules want to get out as quickly as they can. Once the liquid is in our tank it starts to boil or evaporate because propane boils at negative forty-four degrees Fahrenheit. Remember I said it was cold. It is this vapor that is formed from the liquid propane we use in our furnace and other appliances.
Appliances are usually rated in terms of BTU’s or British Thermal Units. My furnace is rated at 40,000 BTUs per hour. A BTU is a measure of the amount of energy required to raise or lower one pound of water one degree. One pound of propane is equal to 21,960 BTUs. My thirty-pound propane tank holds 7.2 gallons of propane weighing approximately 30.24 lbs. This potentially gives me 664,070 BTUs. Remember though, our propane tanks should only be filled to eighty percent of their capacity as room has to be left in the tank for the propane to vaporize and expand. It is the rate of vaporization that can sometimes make it seem like we are out of propane during the wintertime.
In winter, the cold temperatures will affect the rate of vaporization by causing it to slow down. As the temperature gets colder the amount of BTU’s available from our propane will decrease. Continuing with my thirty-pound propane tank let’s assume my tank is sixty percent full. At twenty degrees Fahrenheit the propane will vaporize at a rate that will produce approximately 50,400 BTUs in one hour. When the temperature drops to zero degrees Fahrenheit the rate of vaporization will slow down producing approximately 25,200 BTUs in one hour. Now let’s assume my same propane tank is twenty percent full. At twenty degrees Fahrenheit the rate of vaporization will produce approximately 30,240 BTUs in one hour, while at zero degrees Fahrenheit the rate of vaporization will only produce approximately 15,120 BTUs in one hour.
Earlier I said the furnace in my RV is rated at 40,000 BTUs. That’s 40,000 BTUs consumed per hour if my furnace were to operate continually for one hour. Most RV furnaces are designed to cycle several times per hour and not run continually. However, looking at our example above, if my tank is twenty percent full and it is zero degrees Fahrenheit outside the propane is vaporizing at a rate that only produces approximately 15,120 BTUs per hour. If my furnace ran for five minutes six times per hour it would have run thirty minutes and used approximately 20,000 BTUs of propane. But the rate of vaporization would not have produced that many BTUs, so I could have potentially woken up in the middle of the night to a freezing RV and thought I was out of propane. So, is there anything we can do about this?
One trick when it gets cold is to place an electric blanket around your propane tank. The electric blanket will effectively warm the tank. The warm tank will increase the rate of vaporization which will in turn increase the number of BTUs available in an hour. Additionally, covering your propane tank will help keep them from exposure to windy and wintry conditions. Also, many people, especially if they are stationary, will enclose the bottom of their RV with insulation to help with keeping the inside of the RV as warm as possible. So, the next time you wake up in the middle of the night and your furnace is not keeping you warm it might be time to bring out the electric blanket. Your toasty warm propane tank will thank you for it by increasing the rate of vaporization of the propane producing more BTUs.