I have a 100 lbs propane tank, plan on using it as a back up to my geothermal when it gets -30 to -45 below. Usually only a week or two a year. Wondering if it will work, the tank is outside and will be runnning a 120,000 BTU forced air unit.
If not will a 250 lbs work. Dont need propane other than the gas stove and back up for just a week or two in the winter.
Really dont want to by a 250 if i dont have to.
I doubt a vertical tank of either size will supply enough gas for a furnace that size in the indicated temperatures. You will probably need at least a 250 gallon horizontal tank to get enough liquid to change to a gas for that many BTU. Check with a local supplier, they should know.