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Dutto, how long does a 13kg propane last?
Very much a "How long's a piece of string?" question. It all depends on the amount boiled (for me that is 30 litres to start with), the length of the boil (for me 60 minutes), what you regard as a "rolling boil", the ambient temperature and the wind strength.
I reckon I got
over seven brews out of the last one. At about 40 minutes to bring the wort to the boil (this is when sparging directly into the Boiler) and then boiling it for 60 minutes (sometimes with just the one ring) this correlates with the Burner's maximum output which is rated at 7.5Kw/hr.
Regulators that deliver 1.5kg of Propane/Butane per hour (at 37 mbar and 30 mbar respectively) are perfectly adequate for one of these burners.
Roughly, 1.5Kg of LPG = +/-18,000 Kcal which in turn equals +/-20Kw. At 7.5Kw/hr the restricting factor is the burner output rather than the amount of LPG supplied.
After running out of Propane gas (BP -44 degrees celsius) on the Oatmeal Stout boil just before Christmas, I changed over to Butane gas (BP -4 degrees celsius) and quickly discovered that the ambient temperature was too low to keep the Butane boiling! I then had to go to a local Caravan Site to find a replacement 13kg Propane cylinder before resuming the boil. This is why I now have 2 x Propane bottles (13kg and 7kg) in addition to the 4.5kg Butane one.
Hope this answers the question. :thumb:
PS
If my maths don't stack up I will happily accept major corrections. It's late! :laugh: