Besides the formula in perfect conditions, its also relative to the conditions, different pots, different insulation, different weather, pressure temps, elevation ?? Whether you're using pid pulse or on full power also??, with the lid on or off too
http://e-brewing.tumblr.com/ read down at Fun With Heat Elements and Math he has done some work on the subject with electric only The basic forums looks like this: target temp - start temp = temp rise needed temp rise needed / temp rise per hour provided by element * 60 minutes = minutes needed to reach target temp from start temp with element 220v: Striking: (18766 BTU/h) / 83.4 = 225F / hour 50F rise needed : 50F / 225F rise per hour * 60 min = 13 minutes to strike Boiling: (18766 BTU/h) / 62.55 = 300F / hour 57F rise needed : 57F / 300F * 60 = 11.4 minutes to boil 110v: Striking: (4691.5 BTU/h) / 83.4 = 56.25F / hour 50F / 56.25F * 60min = 53 mins to strike Boil: (4691.5 BTU/h) / 62.55 = 75F / hour 57F / 75F * 60min = 45.6 mins to boil 2x 110v: Striking: (2 * 4691.5 BTU/h) / 83.4 = 112.5F / hour 50F / 112.5F * 60min = 26.5 mins to strike Boil: (2 * 4691.5 BTU/h) / 62.55 = 150F / hour 57F / 150F * 60min = 22.8 mins to boil
See this: http://www.phpdoc.info/brew/boilcalc.html and also cross-referenced to my request today: http://www.brewersfriend.com/forum/viewtopic.php?f=7&t=1085 One issue in the source code of that equation is that when both "Start Temp" and "End Temp" are in units of Farhenheit and "End Temp" exceeds 99F, it always throws an error message of "Start temp cannot be greater than End Temp" even when "Start Temp" is less than "End Temp". It only does it when "End Temp" is in triple digits >=100F and my guess is that it still error checking based on a maximum boiling point of 100C and doesn't recognize hot, but not boiling water temps of 100-212F.
All of that mattters, yes, but the main point is to give electric brewers a ballpark idea of how to size their element or what to expect when mashing, boiling, etc... Real world conditions aside, they'll only affect the difference between boiling with an aluminum pot and a PID heater and boiling with a keggle and a PWM heater by about 5-10%, which equates to only a handful of minutes either way. The more important aspects are insulation and elevation, but even those won't affect the heating times by more than an additional 10-15%. Still well within a ballpark limit of 20% to either side for heating with electric.
posted this on the other post too take it its simple http://spfldmo.com/beer/downloads/boiltime.html http://spfldmo.com/beer/downloads/boiltime.zip
